507 research outputs found
Minicomputer Control of a Latex Reactor
No full textTitle: Minicomputer Control of a Latex Reactor, Author: Stuart W. Ray, Location: ThodeA minicomputer software and hardware system was developed to monitor and control the particle size growth in the emulsion polymerization of vinyl acetate. The basis of the on line detector was a UV spectrophotometer which measured turbidity as a function of wavelength . A preliminary investigation was made to develop a technique for converting turbidity measurements into particle size distributions.ThesisMaster of Engineering (ME
Determinação de arranjos moleculares em cristais líquidos nemáticos utilizando defração de raio-x
No full textDissertaçao (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Curso de Pós-Graduação em Físico-Química
Data from: Inferring the evolution of reproductive isolation in a lineage of fossil threespine stickleback, Gasterosteus doryssus
No full text<p>Darwin attributed the absence of species transitions in the fossil record to his hypothesis that speciation occurs within isolated habitat patches too geographically restricted to be captured by fossil sequences. Mayr's peripatric speciation model added that such speciation would be rapid, further explaining missing evidence of diversification. Indeed, Eldredge and Gould's original punctuated equilibrium model combined Darwin's conjecture, Mayr's model, and 124 years of unsuccessfully sampling the fossil record for transitions. Observing such divergence, however, could illustrate the tempo and mode of evolution during early speciation. Here, we investigate peripatric divergence in a Miocene stickleback fish, <em>Gasterosteus doryssus</em>. This lineage appeared and, over ~8,000 generations, evolved significant reduction of twelve of sixteen traits related to armor, swimming, and diet, relative to its ancestral population. This was greater morphological divergence than we observed between reproductively isolated, benthic-limnetic ecotypes of extant <em>Gasterosteus aculeatus</em>. Therefore, we infer that reproductive isolation was evolving. However, local extinction of low-armoured <em>G. doryssus</em> lineages shows how young isolate populations often disappear, supporting Darwin's explanation for missing evidence and revealing a mechanism behind morphological stasis. Exctinction may also account for limited sustained divergence within the stickleback species complex and help reconcile speciation rate variation observed across time scales.</p><p>Microsoft Excel is helpful to open the data files.</p>
<p>R and R Studio are necessary to run the analysis scripts.</p><p>Funding provided by: National Science Foundation<br>Crossref Funder Registry ID: https://ror.org/021nxhr62<br>Award Number: EAR-2145830</p><p>(a) Fossil specimen data</p>
<p>To quantify morphological divergence in the fossils, we compiled published data from the D (Bell et al. 1985), L (Bell et al. 2006), and K series (Stuart et al. 2020, Voje et al. 2022). See Figure 1A for stratigraphic correlations among series. Series D consisted of 26 samples spaced at ~5,000-year intervals over an estimated 108,275 years (Figure 1A). Six traits were measured from D: standard length, pelvic score, and the number of pre-dorsal pterygiophores, dorsal spines, anal-fin rays, and dorsal-fin rays (Bell et al. 1985). Series L comprised a section starting ~4,500 years before the replacement event until ~16,500 years after and was sampled continuously. Three armour traits were measured for series L: pelvic score, number of dorsal spines, and number of touching pre-dorsal pterygiophores. This series confirmed replacement of lineage I by lineage II within ~125 years (Bell et al. 2006) and that subsequent evolution of lineage II was probably caused by directional natural selection (Hunt et al. 2008). Our analysis focuses on series K (Stuart et al. 2020; Voje et al. 2022) because 16 traits were measured for K (Table S1), allowing estimates of multivariate divergence of traits that should reflect swimming, feeding, and defense. These traits are also divergent between benthic and limnetic ecotypes in the species-pair lakes as well as among allopatric generalist populations of <em>G. aculeatus</em> (Walker 1997; Spoljaric and Reimchen 2007; Willacker et al. 2010). Series K consisted of 18 samples taken at ~1000-year intervals, and mean sample times span ~16,363 years. Series K starts at the replacement, when lineage I and lineage II specimens occurred in a single sample. We removed lineage I fish from this sample for morphological analysis. Traits measured and their sample sizes are provided in Table S1 and Table S2, respectively. Finally, we note that a parapatric, highly armored form with a benthic diet (Bell 2009) was collected from Quarry E (of Brown 1986), approximately 1.7km from the depositional environment studied here. This site was dated to roughly the same time as the K series (Brown 1986) and appears to have been a nearshore sample, based on abundant terrestrial plant fossils and thick clastic layers embedded within the diatomite (Bell 2009). This contrasts the open water habitat that characterized the depositional environment of series D, L, and K (Bell 2009). </p>
<p>(b) Extant specimen data</p>
<p>For comparison to fossil divergence, we measured benthic and limnetic ecotypes from five species-pair lakes (Table 2) for the same 16 traits that were scored in the K-series fossils (Table S1). Specimens were loaned by D. Schluter's lab (University of British Columbia). They collected from Enos Lake in 1988 and from Emily, Little Quarry, Paxton, and Priest Lakes in 2018. The Enos specimens were fixed in formalin and stored in 40% isopropanol. The other specimens were initially preserved in 95% ethanol in the field before being transferred to water then formalin in the lab and stored in 40% isopropanol. In 2019, we stained these specimens for bone using Alizarin Red. Standard length as well as pelvic-spine lengths were measured with calipers. We used a dissection microscope to count dorsal spines, pelvic spines, dorsal-fin rays, and anal-fin rays. Right and left-side pelvic girdle and ectocoracoid lengths were measured from ventral photographs (Canon EOS Rebel T7, Tamron 16-300 mm MACRO lens, Kaiser RS1 copy stand). Lateral X-rays were used to measure dorsal spine length, number of pterygiophores anterior to the pterygiophore holding the third spine, length of the pterygiophore just anterior to the third spine, cleithrum length, and pre-maxilla ascending branch length. We also counted vertebrae from X-rays: abdominal vertebrae were counted anterior to the first vertebra with a haemal spine contacting an anal fin pterygiophore. Caudal vertebrae were posterior, including the first vertebra with the haemal spine contacting the anal fin pterygiophore (Aguirre et al. 2014). X-rays were taken with an AXR Hot Shot X-ray Machine (Associated X-ray Corporation) at the Field Museum of Natural History. Specimens were exposed at 35kV and 4mA for 7 to 10 seconds. We developed the film and scanned individual fish images using the B&W Negatives setting on an Epson Perfection 4990 Photo flatbed at 2400 dpi. Measurements from photographs and X-rays were taken with FIJI (Schindelin et al. 2012) and its plugin ObjectJ (<a href="https://sils.fnwi.uva.nl/bcb/objectj/">https://sils.fnwi.uva.nl/bcb/objectj/</a>). Table S3 reports sample sizes by population, ecotype, and trait.</p>
Data from: Inferring the evolution of reproductive isolation in a lineage of fossil threespine stickleback, Gasterosteus doryssus
No full text<p>Darwin attributed the absence of species transitions in the fossil record to his hypothesis that speciation occurs within isolated habitat patches too geographically restricted to be captured by fossil sequences. Mayr's peripatric speciation model added that such speciation would be rapid, further explaining missing evidence of diversification. Indeed, Eldredge and Gould's original punctuated equilibrium model combined Darwin's conjecture, Mayr's model, and 124 years of unsuccessfully sampling the fossil record for transitions. Observing such divergence, however, could illustrate the tempo and mode of evolution during early speciation. Here, we investigate peripatric divergence in a Miocene stickleback fish, <em>Gasterosteus doryssus</em>. This lineage appeared and, over ~8,000 generations, evolved significant reduction of twelve of sixteen traits related to armor, swimming, and diet, relative to its ancestral population. This was greater morphological divergence than we observed between reproductively isolated, benthic-limnetic ecotypes of extant <em>Gasterosteus aculeatus</em>. Therefore, we infer that reproductive isolation was evolving. However, local extinction of low-armoured <em>G. doryssus</em> lineages shows how young isolate populations often disappear, supporting Darwin's explanation for missing evidence and revealing a mechanism behind morphological stasis. Exctinction may also account for limited sustained divergence within the stickleback species complex and help reconcile speciation rate variation observed across time scales.</p><p>Microsoft Excel is helpful to open the data files.</p>
<p>R and R Studio are necessary to run the analysis scripts.</p><p>Funding provided by: National Science Foundation<br>Crossref Funder Registry ID: https://ror.org/021nxhr62<br>Award Number: EAR-2145830</p><p>(a) Fossil specimen data</p>
<p>To quantify morphological divergence in the fossils, we compiled published data from the D (Bell et al. 1985), L (Bell et al. 2006), and K series (Stuart et al. 2020, Voje et al. 2022). See Figure 1A for stratigraphic correlations among series. Series D consisted of 26 samples spaced at ~5,000-year intervals over an estimated 108,275 years (Figure 1A). Six traits were measured from D: standard length, pelvic score, and the number of pre-dorsal pterygiophores, dorsal spines, anal-fin rays, and dorsal-fin rays (Bell et al. 1985). Series L comprised a section starting ~4,500 years before the replacement event until ~16,500 years after and was sampled continuously. Three armour traits were measured for series L: pelvic score, number of dorsal spines, and number of touching pre-dorsal pterygiophores. This series confirmed replacement of lineage I by lineage II within ~125 years (Bell et al. 2006) and that subsequent evolution of lineage II was probably caused by directional natural selection (Hunt et al. 2008). Our analysis focuses on series K (Stuart et al. 2020; Voje et al. 2022) because 16 traits were measured for K (Table S1), allowing estimates of multivariate divergence of traits that should reflect swimming, feeding, and defense. These traits are also divergent between benthic and limnetic ecotypes in the species-pair lakes as well as among allopatric generalist populations of <em>G. aculeatus</em> (Walker 1997; Spoljaric and Reimchen 2007; Willacker et al. 2010). Series K consisted of 18 samples taken at ~1000-year intervals, and mean sample times span ~16,363 years. Series K starts at the replacement, when lineage I and lineage II specimens occurred in a single sample. We removed lineage I fish from this sample for morphological analysis. Traits measured and their sample sizes are provided in Table S1 and Table S2, respectively. Finally, we note that a parapatric, highly armored form with a benthic diet (Bell 2009) was collected from Quarry E (of Brown 1986), approximately 1.7km from the depositional environment studied here. This site was dated to roughly the same time as the K series (Brown 1986) and appears to have been a nearshore sample, based on abundant terrestrial plant fossils and thick clastic layers embedded within the diatomite (Bell 2009). This contrasts the open water habitat that characterized the depositional environment of series D, L, and K (Bell 2009). </p>
<p>(b) Extant specimen data</p>
<p>For comparison to fossil divergence, we measured benthic and limnetic ecotypes from five species-pair lakes (Table 2) for the same 16 traits that were scored in the K-series fossils (Table S1). Specimens were loaned by D. Schluter's lab (University of British Columbia). They collected from Enos Lake in 1988 and from Emily, Little Quarry, Paxton, and Priest Lakes in 2018. The Enos specimens were fixed in formalin and stored in 40% isopropanol. The other specimens were initially preserved in 95% ethanol in the field before being transferred to water then formalin in the lab and stored in 40% isopropanol. In 2019, we stained these specimens for bone using Alizarin Red. Standard length as well as pelvic-spine lengths were measured with calipers. We used a dissection microscope to count dorsal spines, pelvic spines, dorsal-fin rays, and anal-fin rays. Right and left-side pelvic girdle and ectocoracoid lengths were measured from ventral photographs (Canon EOS Rebel T7, Tamron 16-300 mm MACRO lens, Kaiser RS1 copy stand). Lateral X-rays were used to measure dorsal spine length, number of pterygiophores anterior to the pterygiophore holding the third spine, length of the pterygiophore just anterior to the third spine, cleithrum length, and pre-maxilla ascending branch length. We also counted vertebrae from X-rays: abdominal vertebrae were counted anterior to the first vertebra with a haemal spine contacting an anal fin pterygiophore. Caudal vertebrae were posterior, including the first vertebra with the haemal spine contacting the anal fin pterygiophore (Aguirre et al. 2014). X-rays were taken with an AXR Hot Shot X-ray Machine (Associated X-ray Corporation) at the Field Museum of Natural History. Specimens were exposed at 35kV and 4mA for 7 to 10 seconds. We developed the film and scanned individual fish images using the B&W Negatives setting on an Epson Perfection 4990 Photo flatbed at 2400 dpi. Measurements from photographs and X-rays were taken with FIJI (Schindelin et al. 2012) and its plugin ObjectJ (<a href="https://sils.fnwi.uva.nl/bcb/objectj/">https://sils.fnwi.uva.nl/bcb/objectj/</a>). Table S3 reports sample sizes by population, ecotype, and trait.</p>
Testing the randomness in the sky-distribution of gamma-ray bursts
No full textWe have studied the complete randomness of the angular distribution of gamma-ray bursts (GRBs) detected by the Burst and Transient Source Experiment (BATSE). Because GRBs seem to be a mixture of objects of different physical nature, we divided the BATSE sample into five subsamples (short1, short2, intermediate, long1, long2) based on their durations and peak fluxes, and we studied the angular distributions separately. We used three methods, Voronoi tesselation, minimal spanning tree and multifractal spectra, to search for non-randomness in the subsamples. To investigate the eventual non-randomness in the subsamples, we defined 13 test variables (nine from the Voronoi tesselation, three from the minimal spanning tree and one from the multifractal spectrum). Assuming that the point patterns obtained from the BATSE subsamples are fully random, we made Monte Carlo simulations taking into account the BATSE's sky-exposure function. The Monte Carlo simulations enabled us to test the null hypothesis (i.e. that the angular distributions are fully random). We tested the randomness using a binomial test and by introducing squared Euclidean distances in the parameter space of the test variables. We concluded that the short1 and short2 groups deviate significantly (99.90 and 99.98 per cent, respectively) from the full randomness in the distribution of the squared Euclidean distances; however, this is not the case for the long samples. For the intermediate group, the squared Euclidean distances also give a significant deviation (98.51 per cent)
The electron density: experimental determination and theoretical analysis
No full textTwo related lines of research in experimental electron density determination are reported in this thesis. In the first case, the well-proven and popular multipole modeling technique is applied to three high resolution, single-crystal X-ray diffraction data sets. The preliminary part of this thesis (Chapters 2-5) deals with the theoretical aspects of the multipole model, and also some of the theoretical and practical aspects of data collection and reduction. Chapter 6 reports an experimental charge density determination of a nitrogen ylide. Chapter 7 contains details of the treatment of data from a large, pendant-arm macrocyclic complex of nickel, while Chapter 8 reports the characteristics of the experimentally determined charge density for a substituted acetylene molecule which exhibits interesting intramolecular interactions. The charge densities for all three cases are analysed using Bader's Theory of Atoms in Molecules. The latter part of this thesis deals with more novel ways of treating experimental data. Chapter 9 gives a thorough review of the literature on the application of Maximum Entropy techniques to image reconstruction in general and charge density determination in particular, followed in Chapter 10 by an application to diffraction data from the cubic phase of acetylene. The novel approach of removing core scattering from the data is developed and gives improved results. Chapter 11 reviews some aspects of fermion density matrices and their relationship to electron density functions and X-ray scattering, followed in Chapter 12 by results from the density matrix refinement method applied to diffraction data from formamide. Particular emphasis is placed upon basis set effects, idempotency and various N-representable approximations to the experimentally determined density matrix
Development of a cycle simulation for a coal-fueled, direct-injected, internal combustion engine
No full textTypescript (photocopy).An engine cycle simulation for a coal-fueled internal combustion, reciprocating engine was developed. The primary objective of this work was to develop the simulation for evaluating the viability of coal fuels for engines. The cycle simulation was used to investigate details of the combustion process to identify controlling phenomena and to establish directions for future evaluations. Models for coal particle combustion and devolatilization, liquid droplet vaporization, fuel vapor combustion, cylinder heat transfer, piston work, and mass flow rates were combined with a thermodynamic analysis of the engine to yield instantaneous cylinder conditions and overall indicated engine performance. For selected engine and operating conditions, sensitivity of engine performance on fuel characteristics such as coal reactivity, devolatilization, liquid carriers, atomization, and pilot fuels for ignition were investigated. Several commercially manufactured engines were also simulated with the model. The major conclusions of this work include: (1) devolatilization can have a significant effect on the ignition and combustion processes, (2) liquid carriers can have a significant effect on the ignition and combustion processes, (3) the cylinder gas temperature and pressure at fuel injection are important engine operating parameters for coal fuels, (4) the characteristics of the coal fuel (such as particle size and reactivity) can have a significant impact on the ignition and combustion processes, and (5) the combustion process of coal slurry fuels is largely diffusion (air mixing) controlled
Evaluation of open pit incineration for the disposal of hydrocarbon wastes
No full textDue to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Bibliography: leaves 61-63.Not availabl
Deuterium NMR and x-ray crystallographic studies of guest and host motions in the thiourea/1, 4-di-tert-butylbenzene inclusion compound
No full textDeuterium nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation times are used to investigate the guest and host molecular dynamics of solid 1,4-di-tert-butylbenzene-d4 (DTBB-d4), 1,4-di-tert-butylbenzene-d18 (DTBB-d18), the thiourea/ 1,4-di-tert-butylbenzene-d4 inclusion compound (TU/DTBB-d4), the thiourea/ 1,4-di-tert-butylbenzene-d22 inclusion compound (TU/DTBB-d22), the thiourea-d4/1,4-di-tert-butylbenzene inclusion compound (TU-d4/DTBB), and thiourea-d4 (TU-d4). X-ray crystallographic studies of TU/DTBB-d4 have been carried out at 291 K. In solid DTBB the phenyl ring is essentially static whereas the tert-butyl groups are undergoing rapid reorientation of both methyl and tert-butyl groups. Attempts to analyze the H-2 spectra and T1 data for DTBB-d18 suggest that the dynamics of the methyl and tert-butyl groups are nearly equivalent, and as a result, a satisfactory analysis, yielding methyl and tert-butyl rotational activation energies, was not possible. X-ray diffraction results for TU/DTBB-d4 suggest that, at 291 K, the phenyl ring is occupying three nearly equivalent sites. The H-2 NMR line shapes between 186 and 392 K were interpreted using a model in which the phenyl ring is rapidly flipping between three positions, with one position less favored, At 296 and 186 K the populations are 0.81:1.00:1.00 and 0.20:1.00.1.00, respectively. Relaxation times obtained between 111 and 322 K show no minimum, supporting the assumption of very rapid phenyl ring reorientation. For TU/DTBB-d22 a high-temperature T1 minimum is well-defined, and a second minimum, corresponding to tert-butyl group rotation, is reached at the lowest attainable temperatures. Line-shape simulations of the spectrum at 77 K yield methyl and tert-butyl group rotational rates of 1.0 x 10(3) and 2.0 x 10(6) s-1, respectively. Analysis of the higher temperature spectra (109-172 K) and T1 data (167-300 K) yield methyl rotation activation energies of 12.7 and 12.3 kJ/mol, respectively. Deuterium line-shape studies of the thiourea dynamics in TU-d4 and TU-d4/DTBB yield activation energies for 180-degrees flips about the C=S bond of 47 and 46 kJ/mol, respectively.PT: J; CR: 1974, INT TABLES XRAY CRYS, V4 ARONSON M, 1981, CHEM PHYS, V63, P349 ATWOOD JL, 1984, INCLUSION COMPOUNDS, V1 BECKMANN P, 1979, J MAGN RESON, V36, P199 BECKMANN P, 1981, CHEM PHYS, V63, P359 BECKMANN PA, 1984, J MAGN RESON, V59, P63 BLOEMBERGEN N, 1948, PHYS REV, V73, P679 CANNAROZZI GM, 1991, J PHYS CHEM-US, V95, P1525 CLEMENT R, 1974, J CHEM SOC CHEM COMM, P654 CLEMENT R, 1977, J CHEM PHYS, V67, P5381 COLLINS MJ, 1989, J PHYS CHEM-US, V93, P7495 DAVIS JH, 1976, CHEM PHYS LETT, V42, P390 DAVIS JH, 1991, ISOTOPES PHYSICAL BI, V2, CH2 DRAVERS MA, 1980, CRYST STRUCT COMMUN, V9, P951 ELCOMBE MM, 1968, ACTA CRYSTALLOGR A, V24, P410 FLOVENICIO F, 1976, ACTA CRYSTALLOGR B, V32, P2480 GABE EJ, 1981, ACTA CRYSTALLOGR B, V37, P197 GABE EJ, 1989, J APPL CRYSTALLOGR, V22, P384 GELERINTER E, 1990, J PHYS CHEM-US, V94, P5391 GELERINTER E, 1990, J PHYS CHEM-US, V94, P8845 GOPAL R, 1989, ACTA CRYSTALLOGR C, V45, P257 GREENFIELD MS, 1987, J MAGN RESON, V72, P89 GRIFFIN RG, 1981, METHOD ENZYMOL, V72, P108 GRIFFITH EAH, 1972, CAN J CHEM, V50, P2972 GRUWEL MLH, 1990, Z NATURFORSCH A, V45, P55 HEATON NJ, 1989, J AM CHEM SOC, V111, P3211 HEYES SJ, 1990, MAGN RESON CHEM S, V37 HEYES SJ, 1991, J PHYS CHEM-US, V95, P1547 HOUGH E, 1978, J CHEM SOC DA, P15 HUFFMAN JC, 1990, INORG CHEM, V19, P2749 IKEDA R, 1989, J PHYS CHEM-US, V93, P7315 IWASAKI F, 1979, ACTA CRYSTALLOGR B, V35, P2099 IWASAKI F, 1980, ACTA CRYSTALLOGR B, V36, P1700 JUNGK AE, 1971, CHEM BER, V104, P3289 KENNEDY MA, 1991, J MAGN RESON, V91, P301 KOERFER M, 1989, Z NATURFORSCH A, V44, P1177 KRAVERS MA, 1979, CRYST STRUCT COMMUN, V8, P427 KRAVERS MA, 1980, CRYST STRUCT COMMUN, V9, P955 LIFSHITZ E, 1986, J PHYS CHEM SOLIDS, V47, P1045 LOWERY MD, 1990, J AM CHEM SOC, V112, P4212 MACK JW, 1991, J PHYS CHEM-US, V95, P4207 MAGDOFF BS, 1951, ACTA CRYSTALLOGR, V4, P176 MCDANIEL PL, 1988, J PHYS CHEM-US, V92, P626 MEIROVITCH E, 1987, J PHYS CHEM-US, V91, P5014 NISHIKIORI S, 1990, J PHYS CHEM-US, V94, P8098 OK JH, 1989, J PHYS CHEM-US, V93, P7618 OREILLY DE, 1971, J CHEM PHYS, V54, P1304 POLSON JM, 1991, J CHEM PHYS, V94, P3381 POUPKO R, 1989, J AM CHEM SOC, V111, P6094 POUPKO R, 1991, J PHYS CHEM-US, V95, P407 RATCLIFFE CI, 1990, J PHYS CHEM-US, V94, P152 ROESSLER G, 1989, BER BUNSEN GEN PHYS, V93, P1241 ROY AK, 1990, PROGR NMR SPECTROSCO, V22 SPIESS HW, 1980, J CHEM PHYS, V72, P6755 SPIESS HW, 1985, ADV POLYM SCI, V66, P23 TAKEMOTO K, 1984, INCLUSION COMPOUNDS, V2, CH2 TORCHIA DA, 1981, J MAGN RESON, V42, P381 WASYLISHEN RE, COMMUNICATION WENDOLOSKI JJ, 1990, SCIENCE, V247, P431 WITTEBORT RJ, 1987, J CHEM PHYS, V86, P5411 ZAMIR S, 1991, J CHEM PHYS, V94, P5939; NR: 61; TC: 14; J9: J PHYS CHEM; PG: 9; GA: HY322Source type: Electronic(1
Reynoldsite, Pb_2Mn^(4+)_2O_5(CrO_4), a new phyllomanganate-chromate from the Blue Bell claims, California and the Red Lead mine, Tasmania
No full textThe new mineral reynoldsite, Pb_2Mn^(4+)_2O_5(CrO_4), occurs at the Blue Bell claims, near Baker, San Bernardino County, California, U.S.A., and at the Red Lead mine, Dundas, Tasmania, Australia. At the Blue Bell claims, reynoldsite occurs in subparallel growths and divergent sprays of thin prisms with a square cross section. At the Red Lead mine, it occurs as thin rectangular blades. At both occurrences, crystals are small (≤0.2 mm), and ubiquitously and multiply twinned. At both deposits, reynoldsite formed as a secondary mineral derived from the weathering of primary minerals including oxides and sulfides in the presence of acidic groundwater. Reynoldsite is dark orange-brown to black in color and has a dark orange-brown streak. Its luster is subadamantine and its Mohs hardness is about 4½. The mineral is brittle with irregular to splintery fracture and a poorly developed {001} cleavage. The calculated density is 6.574 g/cm^3 (Red Lead mine). The very high indices of refraction and dark color permitted only partial determination of the transmitted light optical properties. Electron microprobe analyses of Blue Bell and Red Lead reynoldsite provided the empirical formulas (based on nine O atoms): Pb_(1.97)Mn_(2.01)O_5(Cr_(1.01)O_4) and (Pb_(2.07)Sr_(0.04))_(∑2.11)Mn_(2.15)O_5(Cr_(0.87)O_4), respectively. The strongest powder X-ray diffraction lines for Red Lead reynoldsite are [d(hkl)I]: 3.427(021,110)52, 3.254(021,112,121)85, 3.052(112,111,022,103)100, 2.923(013,122)40, 2.5015(004,211,130)47, 1.9818(015,105,202,231)42, 1.7694(115,134,203,142,133)36, and 1.6368(223,043,221,124,224)36. Reynoldsite is triclinic with space group P1 and unit-cell parameters: α = 5.0278(7), b = 7.5865(11), c = 10.2808(15) Å, α = 91.968(12), β = 99.405(12), γ = 109.159(10)°, V = 363.81(9) Å_3, and Z = 2 (for a Red Lead mine crystal). The crystal structure of reynoldsite (R_1 = 10.2% for 902 reflections with F_o > 4σF for a Red Lead crystal) contains close-packed layers of edge-sharing Mn^(4+)O_6 octahedra parallel to {001}. These layers are composed of edge-sharing double chains of octahedra extending along [100], which in turn are linked to one another by sharing edges in the [010] direction. The thick interlayer region contains Pb^(2+) cations and CrO_4 tetrahedra. The 6s^2 lone-electron pair of the Pb^(2+) is stereochemically active, resulting in a one-sided Pb-O coordination arrangement. The structure bears strong similarities to those of the phyllomanganates, such as chalcophanite and birnessite
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