In thermionic-valve diodes, a current through the heater filament indirectly heats the thermionic cathode, another internal electrode treated with a mixture of barium and strontium oxides, which are oxides of alkaline earth metals ; these substances are chosen because they have a small work function.

It is kept under a liquid hydrocarbon such as mineral oil or kerosene to prevent oxidation ; freshly exposed strontium metal rapidly turns a yellowish color with the formation of the oxide.

Although unbinilium is expected to behave typically for an alkaline earth metal, showing a strong + 2 oxidation state, the energetic properties of its valence electrons would increase its ionization energies ; hence, unbinilium may have a lower metallic and ionic radius than expected, and may behave more similarly to calcium and strontium than barium or radium.

In addition, he discovered zirconium, and characterized uranium and zirconium as distinct elements, though he did not obtain any of them in the pure metallic state ; and he elucidated the composition of numerous substances till then imperfectly known, including compounds of the then newly recognized elements: tellurium, strontium, cerium and chromium.

* Scottish chemist Thomas Charles Hope confirms the existence of the alkaline earth metal which he names strontites ; later isolated as strontium.

The strontium unit is a unit used to measure the amount of radioactivity from strontium-90, a radionuclide found in nuclear fallout, in a subject's body ; as the human body absorbs strontium as if it were calcium, incorporating it into the skeleton, its presence is very common.

; Beamline 2C ( BL2C ): used for the Proton Therapy Program to treat choroidal melanomas ( eye tumours ) and proton irradiation to produce strontium isotopes, which are chemically processed and then used for medical imaging generators.

The most studied trace and isotopic signatures are strontium due to the same charge and similar ionic radius to calcium ; however, scientists can study multiple trace elements within an otolith to discriminate more specific signatures.

The United States National Academy of Sciences holds that the maximum safe measure of strontium-90 in a person is one hundred strontium units ( 3700 Bq / kg ).

Cold ion trapping in optical lattices is an experimental tool commonly used in condensed matter as well as atomic, molecular, and optical physics.

The overall accuracy of single trapped ion based optical standards closely approaches that of the state-of-the-art caesium fountain standards.

* National Physical Laboratory: Trapped ion optical frequency standards

Although the electronic transitions of an isolated ion are very well defined, broadening of the energy levels occurs when the ions are incorporated into the glass of the optical fiber and thus the amplification window is also broadened.

Hydroxyl ion absorption is the absorption in optical fibers of electromagnetic waves, including the near-infrared, due to the presence of trapped hydroxyl ions remaining from water as a contaminant.

The hydroxyl ( OH < sup >-</ sup >) ion can penetrate glass during or after product fabrication, resulting in significant attenuation of discrete optical wavelengths, e. g., centred at 1. 383 μm, used for communications via optical fibres.

MCD measurements can detect transitions which are too weak to be seen in conventional optical absorption spectra ; they can also probe paramagnetic properties and the symmetry of the electronic levels of the studied systems, such as metal ion sites.

These are used primarily to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines.

Atomic ion sources are generally modifications of atomic optical spectroscopy atom sources.

; MIS: The Meteorology Instrument System had a temperature sensor, a pressure sensor, a relative humidity sensor, an optical depth sensor ( ODS ) to compare the intensity of direct and scattered sunlight, and an ion anemometer used to detect ion current and atmosphere ionization.

There, the scintillation process is due to an optical transition of the Bi < sup > 3 +</ sup > ion, a major constituent of the crystal.

Protonating or deprotonating a molecule or ion alters many chemical properties beyond the change in the charge and mass: hydrophilicity, reduction potential, optical properties, among others.

This means that optical isomers partition identically into lipid, but have differential effects on ion channels and synaptic transmission.

In a trapped ion system, this is often done using magnetic dipole transitions or stimulated Raman transitions for hyperfine qubits and electric quadrupole transitions for optical qubits.

In 1939 he demonstrated that the major source of optical opacity in the Sun's atmosphere is the H < sup >-</ sup > ion, and thus the main source of visible light for the Sun and stars.

While the previously mentioned methods are focusing on the temperature detection, the inclusion of phosphorescent materials into the thermal barrier coating can also work as a micro probe to detect the aging mechanisms or changes to other physical parameters that affect the local atomic surroundings of the optical active ion.

The NRC attaches a " relative uncertainty " of 2. 5 ( limited by day-to-day and device-to-device reproducibility ) to their atomic clock based upon the < sup > 127 </ sup > I < sub > 2 </ sub > molecule, and is advocating use of an < sup > 88 </ sup > Sr ion trap instead ( relative uncertainty due to linewidth of 2. 2 ).

A proton is transferred from an unspecified Brønsted acid to ammonia, a Brønsted base ; alternatively, ammonia acts as a Lewis base and transfers a lone pair of electrons to form a bond with a hydrogen ion.

In neurons, calcium-sensitive adenylate cyclases are located next to calcium ion channels for faster reaction to Ca < sup > 2 +</ sup > influx ; they are suspected of playing an important role in learning processes.

Bromine is rarer than about three-quarters of elements in the Earth's crust ; however, the high solubility of bromide ion has caused its accumulation in the oceans, and commercially the element is easily extracted from brine pools, mostly in the United States, Israel and China.

According to Brønsted – Lowry acid-base theory, acids are substances that donate a positive hydrogen ion to another substance in a chemical reaction ; by extension, a base is the substance which receives that hydrogen ion.

The concentrations of ions such as sodium and potassium are different in the cytosol than in the extracellular fluid ; these differences in ion levels are important in processes such as osmoregulation and cell signaling.

Larger amounts of radioactive material were later isolated from coral debris of the atoll, which were delivered to the U. S. The separation of suspected new elements was carried out in the presence of a citric acid / ammonium buffer solution in a weakly acidic medium ( pH ≈ 3. 5 ), using ion exchange at elevated temperatures ; fewer than 200 atoms of einsteinium were recovered in the end.

The lithium battery, which does not ( and cannot ) use water in the electrolyte, provides improved performance over other types ; a rechargeable lithium ion battery is an essential part of many mobile devices.

* The ISFET ( ion-sensitive field-effect transistor ) used to measure ion concentrations in a solution ; when the ion concentration ( such as H < sup >+</ sup >, see pH electrode ) changes, the current through the transistor will change accordingly.

The modifiers ( calcium, lead, lithium, sodium, potassium ) alter the network structure ; they are usually present as ions, compensated by nearby non-bridging oxygen atoms, bound by one covalent bond to the glass network and holding one negative charge to compensate for the positive ion nearby.

The high ionic radius of the Pb < sup > 2 +</ sup > ion renders it highly immobile in the matrix and hinders the movement of other ions ; lead glasses therefore have high electrical resistance, about two orders of magnitude higher than soda-lime glass ( 10 < sup > 8. 5 </ sup > vs 10 < sup > 6. 5 </ sup > Ohm · cm, DC at 250 ° C ).

; in most cases the purported rationale is lower current ( less heat ) and or matched ion mobilities, which leads to longer buffer life.

Ions in crystal lattices of purely ionic compounds are spherical ; however, if the positive ion is small and / or highly charged, it will distort the electron cloud of the negative ion, an effect summarised in Fajans ' rules.

* Sodium, a very common electrolyte ; not generally found in dietary supplements, despite being needed in large quantities, because the ion is very common in food: typically as sodium chloride, or common salt.

The status of compounds in which the canonical anion has a delocalized structure in which the negative charge is shared with an atom more electronegative than carbon, as in enolates, may vary with the nature of the anionic moiety, the metal ion, and possibly the medium ; in the absence of direct structural evidence for a carbon – metal bond, such compounds are not considered to be organometallic.

Many ion channel proteins are specialized to select for only a particular ion ; for example, potassium and sodium channels often discriminate for only one of the two ions.

The oxidation of water is catalyzed in photosystem II by a redox-active structure that contains four manganese ions and a calcium ion ; this oxygen-evolving complex binds two water molecules and stores the four oxidizing equivalents that are required to drive the water-oxidizing reaction.

Cryptands, like crown ethers and other ionophores, have a high affinity for the sodium ion ; derivatives of the alkalide Na < sup >-</ sup > are obtainable < ref > by the addition of cryptands to solutions of sodium in ammonia via disproportionation.

Along with potassium, many important medicines have sodium added to improve their bioavailability ; although in most cases potassium is the better ion, sodium is selected for its lower price and atomic weight.

The three main pathways that lead to its activation are GPCR pathways, RTK pathways and gated ion channels ; it regulates proteins either directly or by binding to an enzyme.

Buffer transfer by capillary action from a region of high water potential to a region of low water potential ( usually filter paper and paper tissues ) is then used to move the DNA from the gel on to the membrane ; ion exchange interactions bind the DNA to the membrane due to the negative charge of the DNA and positive charge of the membrane.