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Localized Surface Plasmon Resonance - an overview | ScienceDirect Topics

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In some cases, almost 100% of the light energy can be converted to the second harmonic frequency. These cases typically involve intense pulsed laser beams passing through large crystals, and careful alignment to obtain phase matching.
In other cases, like second-harmonic imaging microscopy, only a tiny fraction of the light energy is converted to the second harmonic—but this light can nevertheless be detected with the help of optical filters.
Generating the second harmonic, often called frequency doubling, is also a process in radio communication; it was developed early in the 20th century, and has been used with frequencies in the megahertz range. It is a special case of frequency multiplication.
An electron (purple) is being pushed side-to-side by a sinusoidally-oscillating force, i.e. the light's electric field. But because the electron is in an anharmonic potential energy environment (black curve), the electron motion is not sinusoidal.
The three arrows show the Fourier series of the motion: The blue arrow corresponds to ordinary (linear) susceptibility, the green arrow corresponds to second-harmonic generation, and the red arrow corresponds to optical rectification.
Electro-optic rectification (EOR), also referred to as optical rectification, is a non-linear optical process that consists of the generation of a quasi-DC polarization in a non-linear medium at the passage of an intense optical beam.
For typical intensities, optical rectification is a second-order phenomenon[1] which is based on the inverse process of the electro-optic effect.
It was reported for the first time in 1962,[2] when radiation from a ruby laser was transmitted through potassium dihydrogen phosphate (KDP) and potassium dideuterium phosphate (KDdP) crystals.
https://t.co/Px03xrubJ0

The term "electro-optic" is often erroneously used as a synonym for "optoelectronic".
Opto-electronics (or optronics) is the study and application of electronic devices and systems that source, detect and control light, usually considered a sub-field of photonics.
In this context, light often includes invisible forms of radiation such as gamma rays, X-rays, ultraviolet and infrared, in addition to visible light.
Optoelectronic devices

are electrical-to-optical

or optical-to-electrical transducers,

or instruments that use such devices in their operation.
Optoelectronics is based on the quantum mechanical effects of light on electronic materials, especially semiconductors, sometimes in the presence of electric fields.
•Photoelectric or photovoltaic effect, used in:
◦photodiodes (including solar cells)
◦phototransistors
◦photomultipliers
◦optoisolators
◦integrated optical circuit (IOC) elements
•Photoconductivity, used in:
◦photoresistors
◦photoconductive camera tubes
◦charge-coupled imaging devices
•Stimulated emission, used in:
◦injection laser diodes
◦quantum cascade lasers
•Lossev effect, or radiative recombination, used in:
◦light-emitting diodes or LED
◦OLEDs
•Photoemissivity, used in
◦photoemissive camera tube
Important applications of optoelectronics include:
•Optocoupler
•Optical fiber communications
An opto-isolator (also called an optocoupler, photocoupler, or optical isolator) is an electronic component that transfers electrical signals between two isolated circuits by using light.
https://t.co/ku83nBU7Ck

An opto-isolator contains a source (emitter) of light, almost always a near infrared light-emitting diode (LED), that converts electrical input signal into light, a closed optical channel (also called dielectrical channel),
and a photosensor, which detects incoming light and either generates electric energy directly, or modulates electric current flowing from an external power supply.
The sensor can be a photoresistor, a photodiode, a phototransistor, a silicon-controlled rectifier (SCR) or a triac. Since LEDs can sense light in addition to emitting it, construction of symmetrical, bidirectional opto-isolators is possible.
An optocoupled solid-state relay contains a photodiode opto-isolator which drives a power switch, usually a complementary pair of MOSFETs.
A slotted optical switch contains a source of light and a sensor, but its optical channel is open, allowing modulation of light by external objects obstructing the path of light or reflecting light into the sensor.
Electronic equipment and signal and power transmission lines can be subjected to voltage surges induced by lightning, electrostatic discharge, radio frequency transmissions,

switching pulses (spikes) and perturbations in power supply.
Transformers and opto-isolators are the only two classes of electronic devices that offer reinforced protection — they protect both the equipment and the human user operating this equipment.
They contain a single physical isolation barrier, but provide protection equivalent to double isolation.

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This nonspecific cation channel opens when illuminated with blue light, depolarizing the cell [4, 6] to trigger action potentials cells with high temporal precision [5]. Since the initial discovery of ChR2, many modifications have been made to refine the kinetic properties.

For example, ChETA, engineered to address limitations of spike fidelity with ChR2, has faster temporal kinetics and can maintain reliable spike precision up to 200 Hz [7].

Halorhodopsins (NpHR), light-gated chloride pumps activated by yellow light, allow for temporally specific hyperpolarization with single spike precision [8–10].

Archaerhodopsin-3 (Arch), a yellow light-activated outward proton pump, is an increasingly popular tool for light-induced hyperpolarization to inhibit cellular activity. Arch recovers spontaneously from inactivation with a much shorter recovery time than NpHRs [11].

Arch currents continue to increase with increasing light intensity, while NpHRs saturate [11]. The increased light sensitivity of the ArchT variant, along with better membrane targeting, allows for improved neural silencing both at cell bodies and terminals [12].
LIFE
NotTheMacAnon
NotTheMacAnon
@NotTheMacAnon1
Transduction is the process by which foreign DNA is introduced into a cell by a virus or viral vector.

Viral vectors are tools commonly used by molecular biologists to deliver genetic material into cells.

Viruses have evolved?

specialized molecular mechanisms

to efficiently

transport their genomes

inside the cells they infect.

Delivery of genes, or other genetic material, by a vector is termed transduction and the infected cells are described as transduced.

A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another.
HEALTH
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@NotTheMacAnon1
In continuum mechanics, stress is a physical quantity that expresses the internal forces that neighbouring particles of a continuous material exert on each other, while strain is the measure of the deformation of the material.

For example, when a solid vertical bar is supporting an overhead weight, each particle in the bar pushes on the particles immediately below it. When a liquid is in a closed container under pressure, each particle gets pushed against by all the surrounding particles.

The container walls and the pressure-inducing surface (such as a piston) push against them in (Newtonian) reaction.

These macroscopic forces are actually the net result of a very large number of intermolecular forces and collisions between the particles in those molecules. Stress is frequently represented by a lowercase Greek letter sigma (σ).

Residual stresses inside a plastic protractor are revealed by the polarized light.
TECH
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👍🏻


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Pott found an association between exposure to soot and a high incidence of scrotal skin cancer in chimney sweeps. This cancer is now known as Pott's or chimney sweep cancer.

Coal contains trace amounts of naturally-occurring radioactive elements. The process of burning coal at coal-fired power plants, called combustion, creates wastes that contain small amounts of naturally-occurring radioactive material (NORM).

Fly ash particles (a major component of coal ash) can become lodged in the deepest part of your lungs, where they trigger asthma, inflammation and immunological reactions.
SONG
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If you shine light of high enough energy on to a metal, electrons will be emitted from the metal.
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Miguel Luengo-Oroz
@litonidas
So proud of my @UNGlobalPulse team and collaborators that step by step and over the years have managed to bring 🤖 science closer to humanitarian and development work. We now have a library!! 📚 📚📚 https://t.co/rOxXQRllo5 Some peer-reviewed highlights in this thread 👇
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Navin Kabra
Navin Kabra
@NGKabra
Did you know that all the nuclear bombs we exploded in the '40s-50s-60s have permanently contaminated all the steel the world has produced since then? All steel in the world is divided into two categories: pre-1945 non-contaminated steel, and post-1945 contaminated steel.

How?

Nuclear bombs (including the tests) create a lot of radioisotopes that are not found in nature. For example Cobalt-60 (a radioactive version of Cobalt-59). And since the 1945 Trinity test, these have all dispersed in the atmosphere.

What does this have to do with steel?

The process of manufacturing steel uses atmospheric air (or atmospheric oxygen). Some of the radioisotopes like Cobalt-60 get pulled in too, and as a result, any steel produced after 1945 has embedded in it some of these radioisotopes, sitting there emitting gamma rays.

Why do we care about traces of radioisotopes in steel? When making Geiger counters, or medical devices to check for radioactive contamination, or astronomical instruments, the emissions from the contaminated steel would interfere with the measurements.

So we need pre-1945 steel

Pre-1945 non-contaminated steel is called "low background steel". And when we need it, where do we get it from?

We go, find pre-World-War-II sunken shipwrecks, and then salvage the steel (and lead) from those to build our instruments which need heavy radiation shielding.
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Mark Tomasovic
Mark Tomasovic
@MarkTomasovic
What is carbon capture? And how does it work?

While carbon capture is regularly discussed in the media, no one really ever explains what it is.

Below is a quick thread discussing the technology behind traditional carbon capture 👇

Carbon capture is broadly the "capture" of CO2 emissions from a power plant or other type of industrial facility.

Technology is connected to the "tailpipes" of these facilities and is used to remove CO2 from the plant exhaust.

Once the CO2 is removed from the plant exhaust, it is typically pressurized and sent under ground for permanent storage.

This step is called "sequestration" and is why experts often talks about "carbon capture and sequestration" or "CCS".

So how do you "capture" the CO2 molecules from exhaust?

Currently, one of the most economic forms of carbon capture is called "amine-based" capture.

An "amine" is a special liquid chemical which selectively grabs on to CO2 molecules.

To get the amine to grab on to the CO2, the amine is put into the top of a large column, while the exhaust is put into the bottom of the column.

The exhaust bubbles up through the column, and the amine drips down.

The liquid amine and gas exhaust mix in the column.
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This is a pretty valiant attempt to defend the "Feminist Glaciology" article, which says conventional wisdom is wrong, and this is a solid piece of scholarship. I'll beg to differ, because I think Jeffery, here, is confusing scholarship with "saying things that seem right".


The article is, at heart, deeply weird, even essentialist. Here, for example, is the claim that proposing climate engineering is a "man" thing. Also a "man" thing: attempting to get distance from a topic, approaching it in a disinterested fashion.


Also a "man" thing—physical courage. (I guess, not quite: physical courage "co-constitutes" masculinist glaciology along with nationalism and colonialism.)


There's criticism of a New York Times article that talks about glaciology adventures, which makes a similar point.


At the heart of this chunk is the claim that glaciology excludes women because of a narrative of scientific objectivity and physical adventure. This is a strong claim! It's not enough to say, hey, sure, sounds good. Is it true?
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6) Asian Paints (decorative paints)
7) Colgate (oral care)
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List of companies with more than 60% Market Share:

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Vibhu Vashisth \U0001f1ee\U0001f1f3
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VEDIC COSMOLOGY, also known as Hindu Cosmology, and cosmography are both interesting and inspiring. Today’s “modern” Vedic texts originated around 3,000 B.C.E. This is the oldest scientific and the oldest religious doctrine known to the human race.


Our current astronomy of the solar system and universe has its roots in Vedic knowledge. It only shows that man had advanced knowledge of astronomy way before our current civilization came into existence.
We are here to talk about the Vedic version of the planetary system,

starting at the top from the eternal planets to the temporary planetary system within innumerable universes in the material world.

Talking about “cosmic manifestation,” we need to incorporate both spiritual and material existence.


The spiritual realm of the planets is everlasting, and this will forever be beyond what the material universe can encapsulate. The spiritual realm belongs to the “super dimensional” or “anti-material” dimension. It means that it is beyond what we can perceive,


beyond time as a linear dimension, and the space of our vision and perception.

There are innumerable planets, all indestructible and forever lasting. That is what the Vedas say about the spiritual planets. Our concentration here is more towards the material side of things.
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