Where does shielding collide?

A conducting enclosure that blocks an external electric or electromagnetic field from reaching the space inside it, because charges in the conductor rearrange to cancel the field within. Faraday's 1838 Experimental researches in electricity, eleventh series reported that a charged conductor holds no electric field in its interior, the observation behind what is now called a Faraday cage. Schelkunoff's 1943 Electromagnetic waves later gave the quantitative theory of how much an enclosure attenuates a passing wave. The referent here is a physical barrier and the field reduction it produces, not the electronic screening of a single nucleus, a deduction that lowers a tax bill, or the mental guarding of a chosen goal.[1][2]

Unit

A shielded enclosure, rated by the field reduction it provides

Recovery means

Not applicable

Measured by

Quantified as shielding effectiveness in decibels, the ratio of field strength without the enclosure to field strength with it

The reduction of the magnetic field felt by an atomic nucleus because the surrounding electrons circulate and generate a small opposing field, so the nucleus resonates at a slightly shifted frequency that depends on its chemical surroundings. Ramsey's 1950 Magnetic shielding of nuclei in molecules set out the theory of this electronic screening and its shielding constant. Proctor and Yu's 1950 The dependence of a nuclear magnetic resonance frequency upon chemical compound reported the shifted frequencies that the screening produces, the basis of the chemical shift used to identify structures. The referent is a molecular electronic effect on one nucleus, measured in parts per million, not a room-sized barrier against a field, a deduction that lowers a tax bill, or the guarding of a goal in the mind.[3][4]

Unit

The screening of one nucleus, expressed as a dimensionless shielding constant

Recovery means

Not applicable

Measured by

Read from the chemical shift in an NMR spectrum, in parts per million relative to a reference compound

The reduction in a company's taxes that comes from an expense being deductible, most often the interest paid on debt, which lowers taxable income and so raises the cash left for investors. Modigliani and Miller's 1963 Corporate income taxes and the cost of capital: A correction showed that because interest is deductible, borrowing creates value equal to the taxes saved, the tax shield of debt. The referent is a financial quantity, the taxes avoided through a deductible cost, valued in currency, and it has nothing in common with a conducting enclosure, the screening of a nucleus, or the protection of a goal.[5]

Unit

The taxes saved by a deductible cost, in currency

Recovery means

Not applicable

Measured by

Estimated as the tax rate times the deductible expense, or as the present value of taxes saved over time

The mental process by which pursuing one goal automatically pushes competing goals and distractions out of mind, so attention stays on the chosen aim. Shah, Friedman, and Kruglanski's 2002 Forgetting all else: On the antecedents and consequences of goal shielding coined the term and showed that activating a focal goal makes alternative goals less accessible, more so when commitment is high. The referent is a cognitive and motivational effect inside a person, measured by how strongly a focal goal suppresses rival ones, not a physical barrier against a field, an electronic screen around a nucleus, or a deduction that lowers a tax bill.[6]

Unit

One person's suppression of competing goals while pursuing a focal goal

Recovery means

Not applicable

Measured by

Assessed in experiments by slowed recognition or reduced accessibility of alternative goals when a focal goal is active