Mu Values Research Articles

Measurement Uncertainty in Fire Tests—A Fire Laboratory Point of View

Since the adoption of ISO/IEC 17025, testing laboratories have been required to perform Measurement Uncertainty analysis for the tests within their scope. Four points of recurring debate are discussed: (1) The variability in fire test results due to unforeseen/uncontrolled variables is generally far greater than the measurement uncertainty of the result. (2) It is important not to confuse “measurement uncertainty” (MU) with “precision” of results. MU has a very specific meaning as used in ISO/IEC 17025, ISO/IEC Guide 98-3 Guide to the Expression of Uncertainty in Measurement (GUM) and ISO Guide 99 International vocabulary of metrology—Basic and general concepts and associated terms (VIM). (3) An uncertainty result is not used to justify passing or failing a product with results very near the pass/fail limit. Where the measured result is subject to a measurement uncertainty evaluation and reporting, compliance limits may or may not require extending the test result by the MU value in making a compliance determination. (4) ISO/IEC 17025 specifically exempts standards that specify limits on sources of uncertainty and specify the form of reporting from a required MU statement. This makes uncertainty estimates inapplicable to those fire tests.

FORMING PLANETESIMALS BY GRAVITATIONAL INSTABILITY. II. HOW DUST SETTLES TO ITS MARGINALLY STABLE STATE

Dust at the midplane of a circumstellar disk can become gravitationally unstable and fragment into planetesimals if the local dust-to-gas density ratio mu is sufficiently high. We simulate how dust settles in passive disks and ask how high mu can become. We settle the dust using a 1D code and test for dynamical stability using a 3D shearing box code. This scheme allows us to explore the behavior of small particles having short but non-zero stopping times in gas: 0 < t_stop << the orbital period. The streaming instability is thereby filtered out. Dust settles until shearing instabilities in the edges of the dust layer threaten to overturn the entire layer. In this state of marginal stability, mu=2.9 for a disk whose bulk (height-integrated) metallicity is solar. For a disk whose bulk metallicity is 4x solar, mu reaches 26.4. These maximum values of mu, which depend on the background radial pressure gradient, are so large that gravitational instability of small particles is viable in disks whose bulk metallicities are just a few (<4) times solar. Earlier studies assumed that dust settles until the Richardson number Ri is spatially constant. Our simulations are free of this assumption but provide support for it within the dust layer's edges, with the proviso that Ri increases with bulk metallicity in the same way that we found in Paper I. Only modest enhancements in bulk metallicity are needed to spawn planetesimals directly from small particles.

Permanent dipole moment of LiCs in the ground state

Recently we demonstrated the formation of ultracold polar LiCs molecules in deeply bound levels of the X1S+ ground state, including the rovibrational ground state [J. Deiglmayr et al., Phys. Rev. Lett. 101, 133004 (2008)]. Here we report on the first experimental determination of the permanent electric dipole moment of deeply bound LiCs molecules. For X1S+,v"=2 and v"=3 we measure values of mu=5.5(2) Debye and 5.3(2) Debye respectively.

A fundamental relation between mass, star formation rate and metallicity in local and high-redshift galaxies

We show that the mass-metallicity relation observed in the local universe is due to a more general relation between stellar mass M*, gas-phase metallicity and SFR. Local galaxies define a tight surface in this 3D space, the Fundamental Metallicity Relation (FMR), with a small residual dispersion of ~0.05 dex in metallicity, i.e, ~12%. At low stellar mass, metallicity decreases sharply with increasing SFR, while at high stellar mass, metallicity does not depend on SFR. High redshift galaxies, up to z~2.5 are found to follow the same FMR defined by local SDSS galaxies, with no indication of evolution. The evolution of the mass-metallicity relation observed up to z=2.5 is due to the fact that galaxies with progressively higher SFRs, and therefore lower metallicities, are selected at increasing redshifts, sampling different parts of the same FMR. By introducing the new quantity mu_alpha=log(M*)-alpha log(SFR), with alpha=0.32, we define a projection of the FMR that minimizes the metallicity scatter of local galaxies. The same quantity also cancels out any redshift evolution up to z~2.5, i.e, all galaxies have the same range of values of mu_0.32. At z>2.5, evolution of about 0.6 dex off the FMR is observed, with high-redshift galaxies showing lower metallicities. The existence of the FMR can be explained by the interplay of infall of pristine gas and outflow of enriched material. The former effect is responsible for the dependence of metallicity with SFR and is the dominant effect at high-redshift, while the latter introduces the dependence on stellar mass and dominates at low redshift. The combination of these two effects, together with the Schmidt-Kennicutt law, explains the shape of the FMR and the role of mu_0.32. The small metallicity scatter around the FMR supports the smooth infall scenario of gas accretion in the local universe.

Mutation Size Optimizes Speciation in an Evolutionary Model

The role of mutation rate in optimizing key features of evolutionary dynamics has recently been investigated in various computational models. Here, we address the related question of how maximum mutation size affects the formation of species in a simple computational evolutionary model. We find that the number of species is maximized for intermediate values of a mutation size parameter μ; the result is observed for evolving organisms on a randomly changing landscape as well as in a version of the model where negative feedback exists between the local population size and the fitness provided by the landscape. The same result is observed for various distributions of mutation values within the limits set by μ. When organisms with various values of μ compete against each other, those with intermediate μ values are found to survive. The surviving values of μ from these competition simulations, however, do not necessarily coincide with the values that maximize the number of species. These results suggest that various complex factors are involved in determining optimal mutation parameters for any population, and may also suggest approaches for building a computational bridge between the (micro) dynamics of mutations at the level of individual organisms and (macro) evolutionary dynamics at the species level.

Effect of substrate feeding on viscosity evolution of anaerobic granular sludges

This work aims to describe the effect of the feeding regime of anaerobic activity tests on the limit viscosity (mu(lim)) evolution of the granules. Batch experiments were performed with 3 different sources of substrate: acetate, peptone, and glucose. Despite, the substrate origin was shown to affect the mu(lim) evolution of granules, no clear relationship was found between the mu(lim) evolution, type of substrate and other granule physico-chemical characteristics (i.e. pH; % of Volatile Suspended Solid; concentration of exopolymeric substances, divalent cations, P and S). The origin of granules and the substrate feeding regime modify the surface shape of the granules and may change granule-granule interactions under a shear stress, thus affecting the evolution of the mu(lim) value during long term reactor operation.

Permanent electric dipole moment of copper monoxide, CuO

A number of low-rotational lines of the A (2)Sigma(-) <-- X (2)Pi(3/2)(0,0) subband of a molecular beam of copper monoxide, CuO, were recorded field free and in the presence of a static electric field. A set of optimized fine and hyperfine parameters for the A (2)Sigma(-)(upsilon(') = 0) state was produced from the analysis of the field-free spectrum. The permanent electric dipole moments mu for the A (2)Sigma(-)(upsilon = 0) and X (2)Pi(3/2)(upsilon = 0) states were determined to be 1.12(71) and 4.57(3) D, respectively, from the analysis of the observed Stark shifts. The error of the experimentally determined mu value for the X (2)Pi(3/2)(upsilon = 0) state is approximately ten times less than that for the previously determined value: mu = 4.45(30) D [T. C. Steimle et al., J. Chem. Phys. 87, 5670 (1987)]. The experimental mu values are compared with theoretical predictions.

SU‐GG‐T‐209: A Novel Method for Further Analysis of IMRT QA

Purpose: IMRT QA is often performed with a commercial device that compares 2D intensity maps to determine if a field passes certain dose and position criteria. The effect of an intensity map error on 3D dosimetry and DVH is clinically relevant but often not considered in IMRT QA. We herein exam the 3D dosimetric impact of IMRT failures measured with a 2D IMRT QA tool. Methods and Materials: 22 IMRT plans had at least one field fail QA using MapCHECK 2, and these were further analyzed using in‐house software to perform a DVH analysis. The MapCHECK 2 passing criteria was 95% of measured points had to be within 5% of the planned dose and have a distance‐to‐agreement of 4mm. Software was installed in our treatment planning system, PlanUNC, that reads intensity maps measured with the MapCHECK 2 and creates DVHs for 3D dose analysis. The software allows for field segment adjustment of MLC positions to address field edge failures and modification of prescribed MUs to address detector points that failed QA. Results: Of the 22 plans that had a field fail initial QA with MapCHECK 2, it was determined that 16/22 and 3/22 plans were within 1% and 2% of the planned CTV and critical structure DVHs. 3/22 plans were found to have DVH differences greater than 2%, and MU values were therefore altered in the treatment plan. Conclusions: Further analysis following an initial IMRT QA with the MapCHECK 2 is often needed to address the 3D dosimetric effects of the measured plan. Software has been installed into PLUNC that allows for 3D analysis for IMRT QA. Our analysis shows that using the MapCHECK 2 passing criteria of dose within 5% and 4mm DTA is sufficient, since 19/22 plans failing this criteria are within 2% of the planned DVH.

Evaluation of [Ln(H2cmp)(H2O)] Metal Organic Framework Materials for Potential Application as Magnetic Resonance Imaging Contrast Agents

Aqueous suspensions of metal organic frameworks (MOF) containing different Ln(3+) ions, consisting of a series of layered Ln(3+) networks formulated as [Ln(H(2)cmp)(H(2)O)] (where H(5)cmp is (carboxymethyl)iminodi(methylphosphonic acid), with a relatively wide size distribution (400 nm to 1 microm) were studied by relaxometry. The water (1)H longitudinal (r(1)) and transverse (r(2)) relaxivities were obtained for aqueous suspensions of these materials with different lanthanide ions. The values of r(1) are very small and varied only slightly with the effective magnetic moment (mu(eff)) of the lanthanide ions, while r(2) values are larger and proportional to the value of mu(eff)(2). The dependence of R(2) on tau(CP) (the time interval between two consecutive refocusing pulses in the train of 180 degrees pulses applied in a CPMG pulse sequence) was evaluated. The value of R(2) initially increases with tau(CP) and then saturates at higher tau(CP) at a value that is about 3 to 5 times lower than R(2p)*. This can be explained by the static dephasing regime (SDR) theory, in which the diffusion effect is taken into account and where the condition tau(D) > Delta omega(r(p))(-1) holds (tau(D) = r(p)(2)/D, where D is the diffusion coefficient, r(p) is the radius of the particle, and Delta omega(r(p)) is the Larmor frequency shift at the particle's surface). Separation of the particles into two fractions with different particle sizes led to a significant enhancement of the r(2) relaxivity of the smaller particles with a narrow size distribution. Magnetometric measurements performed with the particles containing Dy(III), Ho(III), and Gd(III) showed a typical paramagnetic behavior from 4 to 100 K, used to determine the Curie constants.

Hyperfine interaction and Stark effect in the b Π3-X ∑1+(,) band of copper monofluoride, CuF

The low-rotational levels of the b (3)Pi-X (1)Sigma(+)(0,0) band of copper monofluoride, CuF, were recorded field free and in the presence of a static electric field. The field-free spectrum was analyzed to produce a refined set of fine and hyperfine parameters for the b (3)Pi(v=0) state. The permanent electric dipole moment, mu, for the b (3)Pi(v=0) and X (1) summation operator(+)(v=0) states were determined to be 2.36(2) and 5.26(2) D, respectively, from the analysis of the observed Stark shifts. The experimental mu values are compared to theoretical predictions. The change in mu upon excitation and the hyperfine parameters are discussed in terms of the proposed electronic configuration for the b (3)Pi and X (1)Sigma(+) states. The optical Stark spectroscopy of the A (2)Pi(3/2)-X (2)Sigma(+)(0,0) subband of YO was also recorded and analyzed to precisely calibrate the electric field strength. The determined mu values are 3.714(5) and 4.542(40) D for the A (2)Pi(3/2)(v=0) and X (2)Sigma(+)(v=0) states, respectively.

Iron(III) Schiff base complexes of arginine and lysine as netropsin mimics showing AT-selective DNA binding and photonuclease activity

Iron(III) complexes [Fe(L)(2)]Cl (1-3), where L is monoanionic N-salicylidene-arginine (sal-argH for 1), hydroxynaphthylidene-arginine (nap-argH for 2) and N-salicylidene-lysine (sal-lysH for 3), were prepared and their DNA binding and photo-induced DNA cleavage activity studied. Complex 3 as its hexafluorophosphate salt [Fe(sal-lysH)(2)](PF(6)).6H(2)O (3a) was structurally characterized by single crystal X-ray crystallography. The crystals belonged to the triclinic space group P-1. The complex has two tridentate ligands in FeN(2)O(4) coordination geometry with two pendant cationic amine moieties. Complexes 1 and 2 with two pendant cationic guanidinium moieties are the structural models for the antitumor antibiotics netropsin. The complexes are stable and soluble in water. They showed quasi-reversible Fe(III)/Fe(II) redox couple near 0.6V in H(2)O-0.1M KCl. The high-spin 3d(5)-iron(III) complexes with mu(eff) value of approximately 5.9 mu(B) displayed ligand-to-metal charge transfer electronic band near 500nm in Tris-HCl buffer. The complexes show binding to Calf Thymus (CT) DNA. Complex 2 showed better binding propensity to the synthetic oligomer poly(dA).poly(dT) than to CT-DNA or poly(dG).poly(dC). All the complexes displayed chemical nuclease activity in the presence of 3-mercaptopropionic acid as a reducing agent and cleaved supercoiled pUC19 DNA to its nicked circular form. They exhibited photo-induced DNA cleavage activity in UV-A light and visible light via a mechanistic pathway that involves the formation of reactive hydroxyl radical species.

A quantitative analysis of genomic instability in lymphoid and plasma cell neoplasms based on the PIG-A gene

It has been proposed that hypermutability is necessary to account for the high frequency of mutations in cancer. However, historically, the mutation rate (mu) has been difficult to measure directly, and increased cell turnover or selection could provide an alternative explanation. We recently developed an assay for mu using PIG-A as a sentinel gene and estimated that its average value is 10.6 x 10(-7) mutations per cell division in B-lymphoblastoid cell lines (BLCLs) from normal donors. Here we have measured mu in human malignancies and found that it was elevated in cell lines derived from T cell acute lymphoblastic leukemia, mantle cell lymphoma, follicular lymphoma in transformed phase, and 2 plasma cell neoplasms. In contrast, mu was much lower in a marginal zone lymphoma cell line and 5 other plasma cell neoplasms. The highest mu value that we measured, 3286 x 10(-7), is 2 orders of magnitude above the range we have observed in non-malignant human cells. We conclude that the type of genomic instability detected in this assay is a common but not universal feature of hematologic malignancies.

Electron transport properties in fluorinated copper–phthalocyanine films: importance of vibrational reorganization energy and molecular microstructure

Electron transport (ET) properties of a series of fluorinated copper-phthalocyanine (F(16)CuPc) thin films, which were deposited at different substrate temperatures (T(sub)) ranging from 30 to 150 degrees C, have been investigated by quantum mechanical calculations of the reorganization energy (lambda(reorg)), X-ray diffraction (XRD), atomic force microscopy (AFM), and microRaman spectroscopy. Density functional theory calculations were used to predict the vibrational frequencies, normal mode displacement vectors, and electron-vibrational lambda(reorg) for the F(16)CuPc molecule. The electron mobilities (mu(e)) of F(16)CuPc thin films are strongly dependent on the T(sub), and the value of mu(e) increases with increasing T(sub) from 30 to 120 degrees C, at which point it reaches its maximum value. The importance of electron-vibrational coupling and molecular microstructures for ET properties in F(16)CuPc thin films are discussed on the basis of theoretical vibrational lambda(reorg) calculations and experimental observations of resonance Raman spectra. We observed a good correlation between mu(e) and the full-width-at-half-maximum of the vibrational bands, which greatly contributed to lambda(reorg) and/or which reflects the molecular microstructural quality of the active channel. In contrast, the crystal size analysis by XRD and surface grain morphology by AFM did not reveal a clear correlation with the ET behaviours for these different F(16)CuPc thin films. Therefore, we suggest that for organic films with weak intermolecular interactions, such as F(16)CuPc, optimized microscopic molecular-scale parameters are highly important for efficient long-range charge transport in the macroscopic devices.

Correlations of Dietary Crude Protein and Gross Energy on Blood Glucose and Urea, Milk Urea and Lactose Concentrations in Lactating Ewes

Concentrations of serum glucose (SG) and urea (SU), milk lactose (ML) and urea (MU) and their relationships to dietary gross energy (GE) and crude protein (CP) were studied in 16 lactating ewes in Urmia, Iran. Ewes were aged 3 to 5 years and were bred in a closed pen. They were fed alfalfa hay, pasture grass, concentrate and corn silage. Each lactating ewe was nursing a single lamb. Five ml of blood from v. jugularis, 50 ml milk and 200 g feed mixture were collected at 15 day intervals up to 135 days (9 samples). Serum glucose and urea concentrations were evaluated using a spectrophotometer, milk lactose in Polarimeter, gross energy by calculation method and crude protein by Kjeldahl methods. The mean values for dietary GE, CP, SG, SU, MU and ML were 2.39 Mcal/kg/DM, 14.1% food/DM, 2.69, 4.65, 3.67 mmol/l and 4.8 mg/dl milk, respectively. Significant differences (P &lt; 0.01) were found for serum and milk indicators during the milking periods among the sampling times. Serum urea and milk urea irregularly increased while serum glucose and milk lactose irregularly decreased. Positive correlations were found (P &lt; 0.05) between SU/MU (r = 0.45), MU/GE (r = 0.75), MU/CP (r = 0.70) and SU/CP (r = 0.97). Negative correlations (P &lt; 0.05) were found between MU/SG (r = -0.17), SU/ML (r = -0.20) and MU/ML (r = -0.24). Based on results, it is concluded that urea, glucose and lactose would be appropriate variables in the prediction of crude protein and gross energy concentration of diet in lactating ewes.

An extremely rare example of asymmetric tetranuclear core {M4(μ3-X)2(μ-X)4} in a novel alkoxo-bridged heterometallic Cr/Cd complex

A novel heterometallic tetranuclear complex [Cr(3)Cd(NCS)(4)(H(2)tea)(Htea)(3)].3CH(3)OH () has been prepared using cadmium oxide, Reinecke's salt, ammonium thiocyanate and a methanol solution of triethanolamine (H(3)tea) in air. Crystallographic investigations reveal that the molecular structure of the complex is based on an uncommon asymmetric {Cr(3)Cd(mu(3)-O)(2)(mu-O)(4)} core with firstly observed terminal coordination of the NCS-groups in such molecular structure type. A network of O-HO hydrogen bonds as well as SS interactions link the molecules into a two-dimensional supramolecular network. Variable-temperature (1.8-300 K) magnetic susceptibility measurements show a change of the mu(B) value at low temperature, indicative of antiferromagnetic interactions (J = -7.45 cm(-1)) between chromium(iii) centers.

Sampling rate and misidentification of Lévy and non‐Lévy movement paths

A large number of empirical studies have attributed Lévy search patterns to the foraging movements of animals. Typically, this is done by fitting a power-law distribution with an exponent of 1 < mu < or = 3 to the observed step lengths. Most studies record the animal's location at equally spaced time intervals, which are sometimes significantly longer than the natural time scale of the animal's movements. The collected data thus represent a subsample of the animal's movement. In this paper, the effect of subsampling on the observed properties of both Lévy and non-Lévy simulated movement paths is investigated. We find that the apparent properties of the observed movement path can be sensitive to the sampling rate even though Lévy search patterns are supposedly scale-independent. We demonstrate that, in certain contexts and dependent on the sampling rate used in observation, it is possible to misidentify a non-Lévy movement path as being a Lévy path. We also demonstrate that a Lévy movement path can be misidentified as a non-Lévy path, but this is dependent on the value of mu of the original simulated path, with the greatest uncertainty for mu = 2. We discuss the implications of these results in the context of studies of animal movements and foraging behavior.

Inhibition and modulation of rhythmic neuronal spiking by noise

We investigated the effects of noise on periodic firing in the Hodgkin-Huxley nonlinear system. With mean input current mu as a bifurcation parameter, a bifurcation to repetitive spiking occurs at a critical value microc approximately 6.44 . The firing behavior was studied as a function of the mean and variance of the input current, firstly with initial resting conditions. Noise of a small amplitude can turn off the spiking for values of micro close to microc, and the number of spikes undergoes a minimum as a function of the noise level. The robustness of these phenomena was confirmed by simulations with random initial conditions and with random time of commencement of the noise. Furthermore, their generality was indicated by their occurrence when additive noise was replaced by conductance-based noise. For long periods of observation, many frequent transitions may occur from spiking to nonspiking activity when the noise is sufficiently strong. Explanations of the above phenomena are sought in terms of the underlying bifurcation structure and the probabilities that noise shifts the process from the basin of attraction of a stable limit cycle to that of a stable rest state. The waiting times for such transitions depend strongly on the values of mu and sigma and on the forms of the basins of attraction. The observed effects of noise are expected to occur in diverse fields in systems with the same underlying dynamical structure.

The permanent electric dipole moments of cobalt monofluoride, CoF, and monohydride, CoH

The optical Stark spectra of the R(4) and Q(4) lines of the [18.8](3)Phi(4)-X (3)Phi(4)(0,0) band systems of cobalt monofluoride, CoF, and the A(') (3)Phi(4)-X (3)Phi(4)(0,0) band systems of cobalt monohydride, CoH, have been recorded using laser induced fluorescence technique. The shifts and splittings caused by the static electric field have been analyzed to give the permanent electric dipole moments, mu(e), of 4.51(5) and 2.82(5) D for the [18.8](3)Phi(4) and X (3)Phi(4) states of CoF, and 0.01(8) and 1.88(8) D for the A(') (3)Phi(4) and X (3)Phi(4) states of CoH. The experimental dipole moments are compared with theoretical predictions. A molecular orbital correlation description is used to explain the relative ground state mu(e) values for CoH and CoF.

AN OBSERVATIONAL DETERMINATION OF THE PROTON TO ELECTRON MASS RATIO IN THE EARLY UNIVERSE

In an effort to resolve the discrepancy between two measurements of the fundamental constant mu, the proton to electron mass ratio, at early times in the universe we reanalyze the same data used in the earlier studies. Our analysis of the molecular hydrogen absorption lines in archival VLT/UVES spectra of the damped Lyman alpha systems in the QSOs Q0347-383 and Q0405-443 yields a combined measurement of a (Delta mu)/mu value of (-7 +/- 8) x 10^{-6}, consistent with no change in the value of mu over a time span of 11.5 gigayears. Here we define (Delta mu) as (mu_z - mu_0) where mu_z is the value of mu at a redshift of z and mu_0 is the present day value. Our null result is consistent with the recent measurements of King et al. 2009, (Delta mu)/u = (2.6 +/- 3.0) x 10^{-6}, and inconsistent with the positive detection of a change in mu by Reinhold et al. 2006. Both of the previous studies and this study are based on the same data but with differing analysis methods. Improvements in the wavelength calibration over the UVES pipeline calibration is a key element in both of the null results. This leads to the conclusion that the fundamental constant mu is unchanged to an accuracy of 10^{-5} over the last 80% of the age of the universe, well into the matter dominated epoch. This limit provides constraints on models of dark energy that invoke rolling scalar fields and also limits the parameter space of Super Symmetric or string theory models of physics. New instruments, both planned and under construction, will provide opportunities to greatly improve the accuracy of these measurements.

Direct spectroscopic observation of large quenching of first-order orbital angular momentum with bending in monomeric, two-coordinate Fe(II) primary amido complexes and the profound magnetic effects of the absence of Jahn- and Renner-Teller distortions in rigorously linear coordination.

The monomeric iron(II) amido derivatives Fe{N(H)Ar*}(2) (1), Ar* = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Pr(i)(3))(2), and Fe{N(H)Ar(#)}(2) (2), Ar(#) = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Me(3))(2), were synthesized and studied in order to determine the effects of geometric changes on their unusual magnetic properties. The compounds, which are the first stable homoleptic primary amides of iron(II), were obtained by the transamination of Fe{N(SiMe(3))(2)}(2), with HN(SiMe(3))(2) elimination, by the primary amines H(2)NAr* or H(2)NAr(#). X-ray crystallography showed that they have either strictly linear (1) or bent (2, N-Fe-N = 140.9(2) degrees ) iron coordination. Variable temperature magnetization and applied magnetic field Mossbauer spectroscopy studies revealed a very large dependence of the magnetic properties on the metal coordination geometry. At ambient temperature, the linear 1 displayed an effective magnetic moment in the range 7.0-7.50 mu(B), consistent with essentially free ion magnetism. There is a very high internal orbital field component, H(L) approximately 170 T which is only exceeded by a H(L) approximately 203 T of Fe{C(SiMe(3))(3)}(2). In contrast, the strongly bent 2 displayed a significantly lower mu(eff) value in the range 5.25-5.80 mu(B) at ambient temperature and a much lower orbital field H(L) value of 116 T. The data for the two amido complexes demonstrate a very large quenching of the orbital magnetic moment upon bending the linear geometry. In addition, a strong correlation of H(L) with overall formal symmetry is confirmed. ESR spectroscopy supports the existence of large orbital magnetic moments in 1 and 2, and DFT calculations provide good agreement with the physical data.