Limits Of Experimental Uncertainty Research Articles

Binding of plasma low density lipoproteins to erythrocytes

Low density lipoproteins (LDL) containing apolipoprotein B bind to intact, freshly isolated erythrocytes. The LDL-erythrocyte interaction is of low affinity, with a K d of 1.1 · 10 −6 M. Binding is noncooperative. There are about 200 binding sites per cell and, within the limits of experimental uncertainty, these sites comprise a homogeneous class. Binding of LDL is a temperature-independent process. The maximum amount of LDL bound increases following proteolytic digestion of the cells with trypsin or chymotrypsin. The specificity of the binding sites for LDL is not absolute: high density lipoproteins and lipid vesicles composed of phosphatidylcholine or phosphatidylcholine/cholesterol (equimolar) compete with LDL for occupancy of 60% of the binding sites. Modification of 5–6 of the 9 apolipoprotein B arginine residues with 1,2-cyclohexanedione/borate or of 10–15 of the 20 lysine residues by reductive methylation does not alter the ability of LDL to bind to erythrocytes. Native LDL and methylated-LDL alter erythrocyte morphology. However, LDL in which the arginine residues are derivatized with 1,2-cyclohexanedione/borate do not induce the discocyte → echinocyte transformation. Chemically modified and native LDL exchange cholesterol with erythrocytes at equal rates and to nearly equal extents. Taken together, the data suggest that the binding sites for LDL on the erythrocyte membrane are distinct from the LDL receptors at the surface of other cells — e.g., fibroblasts and lymphocytes — which do not bind HDL and which do not recognize LDL with derivatized arginine or lysine residues. It is proposed that the biological function of the erythrocyte binding sites is to mediate the exchange of cholesterol between the cell membrane and lipoproteins.

Geology of the Pyhasalmi ore deposit, Finland

The Pyhaesalmi deposit is a stratabound massive pyrite-copper-zinc deposit in a Precambrian metamorphic schist belt mainly composed of metavolcanites. The host rocks of the ore are silicic fine-grained metavolcanites, and the stratum of ore is stratigraphically overlain by mafic metavolcanites. In the close environment of the ore the silicic metavolcanites, rhyolitic in composition, and the more mafic rocks have been chemically altered; hence, they are enriched in potassium, iron, and magnesium and depleted in sodium and calcium. The metamorphic derivatives of the altered volcanites are sericite schists and cordierite-anthophyllite rocks. The ore deposit, which is syngenetic with silicic volcanites, was folded during polyphase deformation. The orebody averages 0.85 percent Cu, 2.8 percent Zn, 37 percent S, 33 percent Fe, 0.2 g/ton Au, and 14 g/ton Ag. The main gangue minerals are quartz, barite, and local carbonates. The data presented indicate a fairly constant isotope composition of sulfur with an average value of 34 S of +7.5 per mil for pyrite. Isotopic dating of intrusive and supracrustal rocks yields ages of about 1,900 m.y. for the metavolcanites but a somewhat higher age (1,932 + or - 1.5 m.y.) for the gneissic granite, east of the schist belt. The lead isotope compositions of the galena in the Pyhaesalmi ore and its silicic metavolcanite hosts lie on the same isochron within limits of experimental uncertainty. The lead isotopes applied to a plumbotectonic model yield an age of 1.970 m.y. and indicate a mantle origin.

Vacancy properties in gold

A detailed, multi-parameter fitting analysis has been performed on the experimental data available for self-diffusion, equilibrium vacancy concentrations and effective vacancy migration energies, obtained from direct observations of vacancy precipitation after quenching, in gold. The ranges of allowed values for the various vacancy activation enthalpies were determined, within realistic experimental uncertainty limits, to be 0.89 ⩽ EF1V ⩽ 0.96 eV, 0.25 ⩽ EB2v ⩽ 0.57 eV, 0.83 ⩽ EM1V ⩽ ⩽ 0.89 eV, 0.62 ⩽ EM2V ⩽ 0.79 eV and 0.48 ⩽ EM3v ⩽ 0.56 eV. Limits were also obtained for the various pre-exponential or entropy factors. Since within these limits correlations among the possible parameter values exist, the results of the combined analyses are presented as fields in parameter-space. The value of this type of fitting procedure for deducing vacancy defect properties from experiment is discussed. A representative set of allowed vacancy parameters was used to computer-model a quench and subsequent recovery. These calculations demonstrated the self-consistency of the assumption of local equilibrium for the analyses of these vacancy precipitation results.

Charge exchange of metastable 2D oxygen ions with N 2 in the thermosphere

Measurements of N 2 + and supporting data made on the Atmosphere Explorer-C satellite in the ionosphere are used to study the charge exchange process O +( 2 D)+ N 2 → k N + 2+ O The equality k = (5 ± 1.7) × 10 −10cm 3 s −1. This value lies close to the lower limit of experimental uncertainty of the rate coefficient determined in the laboratory. We have also investigated atomic oxygen quenching of O +( 2D) and find that the rate coefficient is 2 × 10 −11 cm 3s −1 to within approximately a factor of two.

Reduced transition probabilities for high-spin states in 232Th

The lifetimes and reduced transition probabilities for spins 6+ − 18+ in the ground-state rotational band of 232Th have been measured by recoil-distance, Doppler-broadened lineshape, and multiple Coulomb excitation methods using 84Kr and 136Xe projectiles. Within the limits of experimental uncertainty, transition probabilities from all of the methods are consistent with those of a good rotor for spins 6+ − 18+. The descrepancy with the prediction of simple β-band mixing and centrifugal stretching models is discussed.

Net ionization coefficient in boron trifluoride

Values of the net ionization coefficient λ1 in BF3 have been determined from spatial current growth measurements in uniform electric fields E over the range 1.07×10−15⩽E/N⩽17.0 ×10−15 V cm2 for gas densities N in the range 4.07×1016 ⩽N⩽348×1016 cm−3. For the limited range 1.07×10−15⩽E/N⩽1.70×10−15 V cm2, values of the ionization and effective attachment coefficients have also been determined. Within the limits of experimental uncertainty all the coefficients are found to be functions of E/N only. The limiting value of E/N at which λl=0 is found to be 1.13×10−15 V cm2.

The thermal expansion of alkali halides at low temperatures - II. Sodium, rubidium and caesium halides

Linear thermal expansions of eleven alkali halides have been determined at room temperature, from 90 to 54 K, and from 30 to 1.5 K. Values are given for the Grüneisen parameter γ = 3 α V / Cx , where α is the linear expansion coefficient, C / V the heat capacity per unit volume, and X is the compressibility. For the four sodium halides γ → γ 0 ≈ 1.0 at the lowest temperature; in NaCl there is evidence of a shallow minimum in γ(T) at about Ɵ D /20. For KCl γ 0 ≈ 0.35, which differs little from our earlier data. Both RbBr and Rbl show a negative expansion below ca . 10 K, having γ 0 ≈ -0.03 and -0.11 respectively, and for RbCl, γ 0 ≈ 0. The limiting values γ 0 agree with γ el 0 , calculated from pressure derivatives of elastic moduli, within limits of experimental uncertainty . CsF which also has NaCl structure was measured but the very limited information about C and X makes γ -values uncertain: approximately γ 0 = 0.3 and γ 283 = 1.7. For CsBr and Csl (each b. c. c.) γ ≈ 2.0 an d is nearly constant.

The low temperature thermal expansion of thallous chloride and thallous bromide

Measurements of the linear coefficients of thermal expansion of TlCl and TlBr are reported between 25 and 260 K. The results are believed to be accurate in an absolute sense to within 2% down to 50K, falling to 6% at 25K. The Gruneisen parameters gamma have been calculated using earlier data on the specific heats and elastic constants, between 260 and 80K. Within this range it is concluded: (i) Any variation of gamma with temperature is within the limits of experimental uncertainty. (ii) Any variation of gamma with ionic mass ratio is within the limits of experimental uncertainty. (iii) The mean room temperature value of gamma for TlCl and TlBr, 2.45+or-0.18, exceeds the corresponding mean value for CsCl, CsBr and CsI, 2.04+or-0.12. Estimates of gamma0based upon the pressure derivatives of the elastic constants at room temperature suggest that for TlBr statement (i) may be extended to T=0, but for TlCl( gamma0- gammainfinity) may exceed unity. Moments of the vibrational frequency spectra of the two crystals have been calculated and varying degrees of consistency with different theoretical models have been observed.

Experimental and theoretical study of “random walk” disorder in mercury(II) amidobromide

Mercury(II) amidobromide can exist in two forms. The stable form at room temperature has an ordered, orthorhombic lattice, whereas in the unstable cubic form the mercury atoms are believed to be disordered with respect to their positions in a way equivalent to a type of random walk disorder in the crystal. The heat capacities of the two forms have been measured from ∼ 10 to ∼ 300 K, giving values of the calorimetric entropy at 25°C. The difference between the actual entropy of the two forms at 25°C has been found from the relation: ΔG=ΔH–TΔS, where ΔH has been determined from heat of solution measurements and ΔG from the e.m.f. of a cell. The value of 131.01 J K–1 mol–1 for the calorimetric entropy of cubic mercury amidobromide at 25°C agrees, within the limits of experimental uncertainty, with that of 130.17 J K–1 mol–1 obtained from the study of the equilibrium between the two forms, which suggests that the cubic form is ordered at the absolute zero.

Thermodynamic investigation of sodium pyrophosphate decahydrate for residual disorder

The heat capacity of sodium pyrophosphate decahydrate has been measured from ∼10 K to ∼300 K. Measurements have also been made, at 25°C, of the heat of solution of the decahydrate and of the anhydrous salt, and of the dissociation pressure in the equilibrium between the decahydrate, anhydrous salt, and water vapour. The value of 164.77 ± 0.2 cal K–1 mol–1 for the entropy of the decahydrate obtained from the heat capacity results agrees, within the limits of experimental uncertainty, with that of 164.62±0.3 cal K–1 mol–1 derived from the equilibrium study. The conclusion that the decahydrate achieves perfect order at 0 K is consistent with previous X-ray structural studies.

Superconductivity of Hydrides and Deuterides of Thorium

Superconductivity has been observed in the hydrides and deuterides of thorium with H-or D-to-metal atom ratios of 3.6 to 3.65. Transition temperatures fall in the range from 8.05 to 8.35 K. These materials are apparently type-II superconductors with ${H}_{c2}$ of the order of 25-30 kG at 1.1 K. There is no evidence for an isotope effect within the limits of experimental uncertainty.

The effect of the wall on the Fricke dosemeter

The influence of the wall on the response of the Fricke dosemeter is discussed and a survey of experimental work on this effect is made. A recent theory of cavity theory is applied to this effect and the results of calculations covering a range of irradiation vessel radii from 0·1 to 5·0 cm and a range of photon energies from 0·20 to 3·0 MeV are presented. Experimental data obtained on a 60Co irradiation unit is compared with these calculations and the agreement is within the limits of experimental uncertainty.

Isobaric spin dependence in proton transfer reactions

Results of an experimental investigation of 54Fe(d, n) 55Co reaction are presented and spectroscopic strengths for both T < and T > states are derived. It is concluded that within the limits of experimental and analytical uncertainties there is no discrepancy between the spectroscopic factors for T > analogue states as derived from the (d, n) and ( 3He, d) reactions.

Corrections to the ft-values of 0 + → 0 + superallowed β-decays

The second-forbidden corrections to superallowed Fermi β-decays are determined by expectation values rather than matrix elements between states of different structure. They partly cancel the corrections arising from violation of isospin symmetry. Within the limits of experimental uncertainty, ( t) corr has the same value for all the decays except that of 26Al.

Volume and Grain-Boundary Diffusion in 20 Cr/25 Ni/Nb Stainless Steel

Abstract Standard radiotracer techniques have been used to measure the volume-diffusion rates of chromium and nickel in a 20 Cr/25 Ni/Nb austenitic steel in the temperature range 840–1290° C. Within the limits of experimental uncertainty, the results are described by D Cr = 0·19 exp (−58·8 × 103/RT), D Ni = 4·06 exp (−67·5 × 103/RT). Grain-boundary-diffusion measurements have been made in the range 550–900° C. The diffusion rates of chromium and nickel isotopes are not significantly different from previously reported values for iron. Combining the data for all three elements gives a mean Arrhenius equation δDB = 1·5 × 10−7 exp (−44 × 103/RT).

A PRELIMINARY INVESTIGATION ON THE ROTATIONAL ENERGY LEVELS OF Mg&lt;sup&gt;24&lt;/sup&gt;

直到目前为止,Mg24的能级、自旋、宇称之在5.24兆电子伏以下者都已准确测定,但对5.24兆电子伏以上者,实验结果尚多分歧。Mg24能级的转动带的特征虽已可肯定,但实验值4.12兆电子伏和从简单的转动能级公式算出的数值4.6兆电子伏的差别,远超过实验误差的范围,对于简单的理论的修正可有两个来源,即振动转动相互作用和转动微扰。本文指出,单考虑一方面的修正不能合理地说明实验事实,只有同时考虑上述两方面的修正才能完满地理解能级的实验结果,并且说明最近测出的γ跃迁分支比和E(2)/M(1)比。

Multiplicity of resonance neutron capture gamma rays

Measurements of the multiplicity of resonance neutron capture gamma rays are reported for 23 resonances of 15 nucleides in the range A = 110 to 198 by comparison with the known multiplicity for B 10 (n, γ) Multiplicities of two resonances forming Eu 152, two resonances forming Er 168, three resonances forming Lu 177 and two resonances forming Hf 178 were not dependent on resonance energy within the limits of experimental uncertainty. Significant variations were found among the multiplicities of three resonances forming In 116 and two resonances forming Sm 150. There is some evidence that J = 3 for the 3.9-eV resonance forming Ho 166. Direct measurements of the resonance J values are not yet available for comparison.

An evaluation of molecular weight distribution in high pressure polyethylene

AbstractA particular kind of plot has been used, yielding graphs tending toward straight lines, to compare the fractionation and viscometry data of eight high pressure polyethylene samples with the distribution formula deduced by Beasley. These graphs are equivalent, except for an additive constant in the abscissas, to the log‐log plots of intrinsic viscosity versus molecular weights. In this way an evaluation of the distribution parameters defined by Beasley can be obtained for all the investigated samples. By means of these parameters and the absolute determination of the (number‐)average molecular weight of a single sample, an evaluation of all the molecular weights and of their distribution in the given samples has been proposed. Within the limits of experimental uncertainty of the measurements of high pressure polyethylene in diluted solutions, these results are in some agreement with the experimental findings of other authors.