Are genes units of inheritance

ABSTRACT: Definitions of the term 'gene' typically superimpose molecular genetics onto Mendelism. What emerges are persistent attempts to regard the gene as a 'unit' of structure and/or function, language that creates multiple meanings for the term and fails to acknowledge the diversity of gene architecture. I argue that coherence at the molecular level requires abandonment of the classical unit concept and recognition that a gene is constructed from an assemblage of domains. Hence, a domain set (1) conforms more closely to empirical evidence for genetic organization of DNA regions capable of transcription and (2) has ontological properties lacking in the traditional unit definition

Temperature dependence of the magnetostriction and magnetoelastic coupling in Fe100−xAlx (x = 14.1,16.6,21.5,26.3) and Fe50Co50

In this paper, we report magnetostriction measurements, (λ100) on Fe-rich Fe–Al alloys and Fe50Co50 as functions of temperature from 77 K to room temperature (RT). From these measurements and elastic constant (c′) measurements, the tetragonal magnetoelastic coupling constants (b1’s) were calculated. Significant differences were found between our RT measurements and earlier magnetostriction measurements for the higher Al concentration alloys (16.6%, 21.5%, 26.3% Al) and the Fe50Co50 alloy. Reminiscent of the temperature dependence of λ100 for pure Fe, magnetostriction changes with temperature are minimal for Fe–Al alloys having the disordered bcc (A2)structure (x\u3c19% Al). In contrast, the alloy possessing the ordered (D03) structure shows an anomalous decrease in magnetostriction in λ100 with decreasing temperature. For the Fe–Al alloy system, the magnetoelastic coupling constant, ∣b1∣, exhibits a peak at room temperature maximizing at 16.6% Al with a value of 12.3 MJ/m3. For Fe50Co50, ∣b1∣ was calculated to be ∼ 34 MJ/m3 at room temperature

Effect of interstitial additions on magnetostriction in Fe–Ga alloys

The additions of trace amounts of small interstitial atoms (carbon, boron, and nitrogen) to Fe–Ga (Galfenol) alloys have a small but beneficial effect on the magnetostriction of Fe–Ga alloys especially at high Ga compositions. The saturated magnetostrictions [(3/2)λ100’s] of both slow cooled and quenched single crystal Fe–Ga–C alloys with Ga contents \u3e18 at. % are about 10%–30% higher than those of the comparable binary Fe–Ga alloys. For boron and nitrogen additions, the magnetostrictions of slow cooled alloys with Ga content \u3e18 at. % were approximately 20% higher than those of the binary Fe–Ga alloys. We assume that these small atoms enter interstitially into the octahedral site as in pure α-Fe and inhibit chemical ordering, resulting in increased λ100. Thermal analysis of the Fe–Ga binary alloys and Fe–Ga–C ternary alloys indicates that the addition of C into the Fe–Ga system decreases the formation kinetics of D03 and extends the disordered region beyond the maximum for slow cooled binary samples

Quasi-Static Transduction Characterization of Galfenol

The objective of the work presented is characterization of the magnetoelastic transduction properties of single crystal and textured polycrystalline Fe-Ga alloys (Galfenol) under controlled mechanical, magnetic and thermal conditions. Polycrystalline samples of interest include a directionally solidified specimen, which possesses a favorable saturation magnetostriction output, and an extruded specimen, whose magnetostriction properties were significantly reduced by annealing. A brief discussion of the thermally controlled transducer used for the magnetic testing is presented first. Thereafter, the single crystal response to major-loop cyclic magnetic fields under different temperature and stress conditions, as well as its response to minor-loop cyclic magnetic fields and major-loop cyclic stress is examined. Next, the magnetic and magnetostrictive responses to major-loop cyclic magnetic field conditions are compared for the directionally solidified, extruded and single crystal specimens. The paper concludes with a magnetic characterization summary of the different Fe-Ga alloys examined

Temperature and stress dependencies of the magnetic and magnetostrictive properties of Fe0.81Ga0.19

It was recently reported that the addition of nonmagnetic Ga increased the saturation magnetostriction (λ100) of Fe over tenfold while leaving the rhombohedral magnetostriction (λ111) almost unchanged. To determine the relationship between the magnetostriction and the magnetization we measured the temperature and stress dependence of both the magnetostriction and magnetization from −21 °C to +80 °C under compressive stresses ranging from 14.4 MPa to 87.1 MPa. For this study a single crystal rod of Fe0.81Ga0.19 was quenched from 800 °C into water to insure a nearly random distribution of Ga atoms. Constant temperature tests showed that compressive stresses greater than 14.4 MPa were needed to achieve the maximum magnetostriction. For the case of a 45.3 MPa compressive stress and applied field of 800 Oe, the maximum magnetostriction at 80 °C decreases from its value at −21 °C by 12.9%. This small magnetostrictive decrease is consistent with a correspondingly small 3.6% decrease in magnetization over the same temperature range. This well-behaved temperature response makes this alloy particularly valuable for industrial and military smart actuator, transducer, and active damping applications. The measured value of Young’s modulus is low (∼55±1 GPa) and almost temperature independent. The large magnetostriction over a wide temperature range combined with the nonbrittle nature of the alloy is rare

Magnetostriction and elasticity of body centered cubic Fe100−xBex alloys

Magnetostriction measurements from 77 K to room temperature on oriented (100) and (110) disk samples of Fe93.9Be6.1 and Fe88.7Be11.3 reveal substantial increases in λ100compared to iron. For the 11.3% alloy, λ100=110 ppm, a sixfold increase above that of α-Fe. For the 6.1% alloy, λ100=81 ppm, ∼40% and ∼170% greater than λ100 of comparable Fe–Ga and Fe–Al alloys, respectively, for H=15 kOe. Large differences exist between the values of λ100 and λ111 (λ100\u3e0, λ111\u3c0) and their temperature dependencies. Elastic constants, c11, c12, and c44, from 4 to 300 K were obtained on the same Fe–Be alloys. From these measurements, the magnetoelastic energy coefficients b1 and b2 were calculated. While the magnitudes of the magnetostrictions λ100 and λ111 are widely different, the magnitudes of b1 and b2 are within a factor of 2. The Fe–Be alloys are highly anisotropic magnetostrictively, elastically, and magnetoelastically. For Fe88.7Be11.3 at room temperature λ100/λ111, 2c44/(c11−c12), and b1/b2 are −6.6, 3.55, and −1.86, respectively

Magnetostrictive and piezomagnetic properties of Tb1-xDyx Zn at low temperatures

Tb1-xDyxZn(0 axes can be changed to very hard \u3c100\u3e axes by increasing x from 0 to 1. (In fact, the existence of a near zero magnetic anisotropy by the proper choice of x is the origin of the well-known Terfenol-D alloys, Tb1-xDyxFe2). The Tb$1-x)DyxZn system discussed here is particularly attractive because of the simplicity of its crystal structure (CsCl), its relatively high Curie temperatures (for rare earth alloys), and the existence of a large (uv0) phase for T \u3c 50K. A summary of some of the important properties of these three alloy systems is given in Table I. In all these systems, at least one of the magnetostriction constraints is very large

Temperature dependence of the magnetic anisotropy and magnetostriction of Fe100−xGax (x = 8.6, 16.6, 28.5)

The temperature dependence of the lowest order magnetic anisotropy constant K1 and the lowest order saturation magnetostriction constant, (3/2)λ100, were measured from 4 K to 300 K for Fe91.4Ga8.6,Fe83.4Ga16.6, and Fe71.5Ga28.5 and were compared to the normalized magnetization power law, ml(l+1)/2. Fe91.4Ga8.6 maintains the magnetostriction anomaly of Fe (dλ100/dT\u3e0) and K1 is a reasonable fit to the ml(l+1)/2power law with K1(0 K) ≅ 90 kJ/m3. Fe83.4Ga16.6 does not show a magnetostriction anomaly, but fits the power law remarkably well. Fe71.5Ga28.5 possesses a small K1( ∼ 1 kJ/m3) at all temperatures and a large temperature dependent magnetostriction, reaching ∼ 800 ppm at low temperature

Magnetoelastic coupling in Fe100−xGex single crystals with 4

In this paper we examine the elastic (c′ and c44) and magnetostrictive (λ100 and λ111) behaviors of Fe100−xGex for 4\u3cx\u3c18, quantities used further to find the fundamental magnetoelastic coupling constants b1 and b2 at room temperature. The x dependence ofb1 and b2 for Fe100−xGex is contrasted to those of Fe100−xGax and Fe100−xAlx. While the rhombohedral shear elastic constant c44 is almost insensitive to the type and amount of solute, the tetragonal shear constant c′ shows a pronounced and rapid softening with increasing x for all three alloys but with different decreasing slopes. Similarly, while the rhombohedral magnetostriction λ111 behavior is analogous for all three alloy systems, showing a sign change from negative to positive at the onset of chemical order, the tetragonal magnetostriction λ100 behavior differs. For the Ga and Al alloys, λ100 maintains positive values over the entire x range, both curves showing large peak values, whereasλ100 of Fe100−xGex exhibits a moderate positive peak followed by a negative dip, both of comparable magnitude. Finally the tetragonal coupling constant −b1 of Fe–Ge shows a marked, sharp decrease as chemical order occurs at x ∼ 12 at. % Ge. The decline continues until the ordered D03 phase is fully established at x ∼ 18 at. % Ge. The peak value of |b1| for Fe–Ge is approximately half of those for Fe–Ga and Fe–Al. This smaller value of |b1|, obtained for the higher electron concentration Ge alloy, is consistent with predictions based on band structure calculations. The rhombohedral coupling constant−b2 shows a consistent sign change at the occurrence of chemical ordering in both Fe–Ga and Fe–Ge