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1. The DANish Comorbidity Index for Acute Myocardial Infarction (DANCAMI): Development, Validation and Comparison with Existing Comorbidity Indices

Author

Wellejus Albertsen L, Heide-Jørgensen U, Schmidt SAJ, Grey C, Jackson R, Sørensen HT, and Schmidt M

Subjects
comorbidity, myocardial infarction, prognosis, risk score, Infectious and parasitic diseases, RC109-216
Abstract

Lisbeth Wellejus Albertsen,1 Uffe Heide-Jørgensen,1 Sigrun Alba Johannesdottir Schmidt,1 Corina Grey,2 Rod Jackson,2 Henrik Toft Sørensen,1 Morten Schmidt1,3,4 1Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark; 2Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand; 3Department of Cardiology, Regional Hospital West Jutland, Herning, Denmark; 4Department of Cardiology, Aarhus University Hospital, Aarhus, DenmarkCorrespondence: Morten Schmidt Email Morten.schmidt@clin.au.dkObjective: To develop and validate the DANish Comorbidity index for Acute Myocardial Infarction (DANCAMI) for adjustment of comorbidity burden in studies of myocardial infarction prognosis.Methods: Using medical registries, we identified patients with first-time myocardial infarction in Denmark during 2000– 2013 (n=36,685). We developed comorbidity indices predicting 1-year all-cause mortality from all comorbidities (DANCAMI) and restricted to non-cardiovascular comorbidities (rDANCAMI). For variable selection, we eliminated comorbidities stepwise using hazard ratios from multivariable Cox models. We compared DANCAMI/rDANCAMI with Charlson and Elixhauser comorbidity indices using standard performance measures (Nagelkerke’s R2, Harrell’s C-statistic, the Integrated Discrimination Improvement, and the continuous Net Reclassification Index). We assessed the significance of the novel DANCAMI variables not included in the Charlson Comorbidity Index. External validation was performed in patients with myocardial infarction in New Zealand during 2007– 2016 (n=75,069).Results: The DANCAMI included 24 comorbidities. The rDANCAMI included 17 non-cardiovascular comorbidities. In the Danish cohort, the DANCAMI indices outperformed both the Charlson and the Elixhauser comorbidity indices on all performance measures. The DANCAMI indices included multiple variables that were significant predictors of 1-year mortality even after controlling for all variables in the Charlson Comorbidity Index. These novel variables included valvular heart disease (hazard ratio for 1-year mortality=1.25, 95% CI: 1.14– 1.35), coagulopathy (1.13, 95% CI: 1.05– 1.22), alcohol and drug abuse (1.35, 95% CI: 1.15– 1.58), schizophrenia (1.60, 95% CI: 1.46– 1.76), affective disorder (1.29, 95% CI: 1.22– 1.36), epilepsy (1.26, 95% CI: 1.05– 1.50), neurodegenerative disorder (1.30, 95% CI: 1.10– 1.54) and chronic pancreatitis (1.71, 95% CI: 1.14– 2.56). The results were supported by the external validation in New Zealand.Conclusion: DANCAMI assessed comorbidity burden of patients with first-time myocardial infarction, outperformed existing comorbidity indices, and was generalizable to patients outside Denmark. DANCAMI is recommended as a standard approach for comorbidity adjustment in studies of myocardial infarction prognosis.Keywords: comorbidity, myocardial infarction, prognosis, risk score

Published
2020

2. Transesterification vegetable oils using heterogeneous catalysts

Author

Grey C. Castellar Ortega, Edgardo R. Angulo Mercado, and Beatriz M. Cardozo Arrieta

Subjects
Biodiesel, Transesterificación, Triacilglicéridos, Catálisis, Sitio activo., Mechanical engineering and machinery, TJ1-1570
Abstract

El progresivo aumento en los precios del petróleo y el agotamiento de sus reservas ha motivado a la sociedad científica a pensar en combustibles alternativos y renovables como el biodiesel. La producción de biodiesel se lleva a cabo principalmente por transesterificación de triacilglicéridos (aceites vegetales y grasas animales) y un alcohol liviano en presencia de catalizadores. Los catalizadores homogéneos tipo hidróxidos de sodio o de potasio son típicamente los más empleados en la producción de biodiesel; desafortunadamente problemas asociados principalmente con el aumento de costos debido a la implementación de etapas de separación y el tratamiento posterior de aguas residuales, ha enfocado la atención de los investigadores hacia el empleo de catalizadores heterogéneos. Este artículo presenta una revisión sobre tres tipos de catalizadores heterogéneos, los óxidos de metales alcalinotérreos, las zeolitas y los heteropoliácidos, empleados en reacciones de transestrificación de aceites para la obtención de biodiesel. En términos generales, estos catalizadores han demostrado ser eficientes, selectivos, fáciles de separar, reutilizables y algunos más que otros, tolerables a la presencia de agua y de ácidos grasos libres.

Published
2014
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3. Oxygen Hole Formation Controls Stability in LiNiO$_2$ Cathodes: DFT Studies of Oxygen Loss and Singlet Oxygen Formation in Li-Ion Batteries

Author

Genreith-Schriever, A. R., Banerjee, H., Menon, A. S., Bassey, E. N., Piper, L. F., Grey, C. P., and Morris, A. J.

Subjects
Condensed Matter - Materials Science
Abstract

Ni-rich cathode materials achieve both high voltages and capacities in Li-ion batteries but are prone to structural instabilities and oxygen loss via the formation of singlet oxygen. Using ab initio molecular dynamics simulations, we observe spontaneous O$_2$ loss from the (012) surface of delithiated LiNiO$_2$, singlet oxygen forming in the process. We find that the origin of the instability lies in the pronounced oxidation of O during delithiation, i.e., O plays a central role in Ni O redox in LiNiO$_2$. For LiNiO$_2$, NiO$_2$, and the prototype rock salt NiO, density-functional theory and dynamical mean-field theory calculations based on maximally localised Wannier functions yield a Ni charge state of ca. +2, with O varying between -2 (NiO), -1.5 (LiNiO$_2$) and -1 (NiO$_2$). Predicted XAS Ni $K$ and O $K$-edge spectra are in excellent agreement with experimental XAS spectra, confirming the predicted charge states. The calculations also show that a high-voltage O $K$-edge feature at 531 eV previously assigned to lattice O-redox processes could alternatively arise from O-redox induced water intercalation and O-O dimer formation with lattice O at high states of charge. The O$_2$ surface loss route observed here consists of 2 surface O$^{.-}$ radicals combining to form a peroxide ion, which is oxidised to O$_2$, leaving behind 2 O vacancies and 2 O$^{2-}$ ions: effectively 4 O$^{.-}$ radicals disproportionate to O$_2$ and 2 O$^{2-}$ ions. The reaction liberates ca. 3 eV per O$_2$ molecule. Singlet oxygen formation is caused by the singlet ground state of the peroxide ion, with spin conservation dictating the preferential release of $^1$O$_2$, the strongly exergonic reaction providing the free energy required for the formation of $^1$O$_2$ in its excited state.

Published
2022
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4. Sample Dependence of Magnetism in the Next Generation Cathode Material LiNi$_{0.8}$Mn$_{0.1}$Co$_{0.1}$O$_2$

Author

Mukherjee, P., Paddison, J. A. M., Xu, C., Ruff, Z., Wildes, A. R., Keen, D. A., Smith, R. I., Grey, C. P., and Dutton, S. E.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons
Abstract

We present a structural and magnetic study on two batches of polycrystalline LiNi$_{0.8}$Mn$_{0.1}$Co$_{0.1}$O$_2$ (commonly known as Li NMC 811), a Ni-rich Li ion battery cathode material, using elemental analysis, X-ray and neutron diffraction, magnetometry, and polarised neutron scattering measurements. We find that the samples, labelled S1 and S2, have the composition Li$_{1-x}$Ni$_{0.9+x-y}$Mn$_y$Co$_{0.1}$O$_2$, with $x = 0.025(2)$, $y = 0.120(2)$ for S1 and $x = 0.002(2)$, $y = 0.094(2)$ for S2, corresponding to different concentrations of magnetic ions and excess Ni$^{2+}$ in the Li$^+$layers. Both samples show a peak in the zero-field cooled (ZFC) dc susceptibility at 8.0(2) K but the temperature at which the ZFC and FC (field-cooled) curves deviate is substantially different: 64(2) K for S1 and 122(2) K for S2. Ac susceptibility measurements show that the transition for S1 shifts with frequency whereas no such shift is observed for S2 within the resolution of our measurements. Our results demonstrate the sample dependence of magnetic properties in Li NMC 811, consistent with previous reports on the parent material LiNiO$_2$. We further establish that a combination of experimental techniques are necessary to accurately determine the chemical composition of next generation battery materials with multiple cations., Comment: Revised manuscript, 27 pages main text, 6 figures, 5 pages supplementary material. Accepted for publication in Inorganic Chemistry

Published
2020
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6. The effect of interface heterogeneity on zinc metal anode cyclability.

Author

Simon, J. T., Šedajová, V., Tripathy, D., Smith, H. E., Clarke, S. M., Grey, C. P., and Menkin, S.

Abstract

Zinc metal batteries (ZMBs) are promising candidates for low-cost, intrinsically safe, and environmentally friendly energy storage systems. However, the anode is plagued with problems such as the parasitic hydrogen evolution reaction, surface passivation, corrosion, and a rough metal electrode morphology that is prone to short circuits. One strategy to overcome these issues is understanding surface processes to facilitate more homogeneous electrodeposition of zinc by guiding the alignment of electrodeposited zinc. Using Scanning Electrochemical Microscopy (SECM), the charge transport rate on zinc metal anodes was mapped, demonstrating that manipulating electrolyte concentration can influence zinc electrodeposition and solid electrolyte interphase (SEI) formation in ZMBs. Using XPS and Raman spectroscopy, it is demonstrated that an SEI is formed on zinc electrodes at neutral pH, composed primarily of a Zn4(OH)6SO4·xH2O species, its formation being attributed to local pH increases at the interface. This work shows that more extended high-rate cycling can be achieved using a 1 M ZnSO4 electrolyte and that these systems have a reduced tendency for soft shorts. The improved cyclability in 1 M ZnSO4 was attributed to a more homogeneous and conductive interface formed, rather than the bulk electrolyte properties. This experimental methodology for studying metal battery electrodes is transferable to lithium metal and anode-free batteries, and other sustainable battery chemistries such as sodium, magnesium, and calcium. [ABSTRACT FROM AUTHOR]

Published
2024
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7. Thermodynamically stable lithium silicides and germanides from density-functional theory calculations

Author

Morris, Andrew J., Grey, C. P., and Pickard, C. J

Subjects
Condensed Matter - Materials Science
Abstract

Density-functional-theory (DFT) calculations have been performed on the Li-Si and Li-Ge systems. Lithiated Si and Ge, including their metastable phases, play an important technological r\^ole as Li-ion battery (LIB) anodes. The calculations comprise structural optimisations on crystal structures obtained by swapping atomic species to Li-Si and Li-Ge from the X-Y structures in the International Crystal Structure Database, where X={Li,Na,K,Rb,Cs} and Y={Si,Ge,Sn,Pb}. To complement this at various Li-Si and Li-Ge stoichiometries, ab initio random structure searching (AIRSS) was also performed. Between the ground-state stoichiometries, including the recently found Li$_{17}$Si$_{4}$ phase, the average voltages were calculated, indicating that germanium may be a safer alternative to silicon anodes in LIB, due to its higher lithium insertion voltage. Calculations predict high-density Li$_1$Si$_1$ and Li$_1$Ge$_1$ $P4/mmm$ layered phases which become the ground state above 2.5 and 5 GPa respectively and reveal silicon and germanium's propensity to form dumbbells in the Li$_x$Si, $x=2.33-3.25$ stoichiometry range. DFT predicts the stability of the Li$_{11}$Ge$_6$ $Cmmm$, Li$_{12}$Ge$_7$ $Pnma$ and Li$_7$Ge$_3$ $P32_12$ phases and several new Li-Ge compounds, with stoichiometries Li$_5$Ge$_2$, Li$_{13}$Ge$_5$, Li$_8$Ge$_3$ and Li$_{13}$Ge$_4$., Comment: 10 pages, 5 figures

Published
2014
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8. Lithiation of silicon via lithium Zintl-defect complexes

Author

Morris, Andrew J., Needs, R. J., Salager, Elodie, Grey, C. P., and Pickard, Chris J.

Subjects
Condensed Matter - Materials Science
Abstract

An extensive search for low-energy lithium defects in crystalline silicon using density-functional-theory methods and the ab initio random structure searching (AIRSS) method shows that the four-lithium-atom substitutional point defect is exceptionally stable. This defect consists of four lithium atoms with strong ionic bonds to the four under-coordinated atoms of a silicon vacancy defect, similar to the bonding of metal ions in Zintl phases. This complex is stable over a range of silicon environments, indicating that it may aid amorphization of crystalline silicon and form upon delithiation of the silicon anode of a Li-ion rechargeable battery., Comment: 4 pages, 3 figures

Published
2013
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9. Energetics of hydrogen/lithium complexes in silicon analyzed using the Maxwell construction

Author

Morris, Andrew J., Grey, C. P., Needs, R. J., and Pickard, Chris J.

Subjects
Condensed Matter - Materials Science
Abstract

We have studied hydrogen/lithium complexes in crystalline silicon using density-functional-theory methods and the ab initio random structure searching (AIRSS) method for predicting structures. A method based on the Maxwell construction and convex hull diagrams is introduced which gives a graphical representation of the relative stabilities of point defects in a crystal and enables visualization of the changes in stability when the chemical potentials are altered. We have used this approach to study lithium and hydrogen impurities in silicon, which models aspects of the anode material in the recently-suggested lithium-ion batteries. We show that hydrogen may play a role in these anodes, finding that hydrogen atoms bind to three-atom lithium clusters in silicon, forming stable {H,3Li} and {2H,3Li} complexes, while the {H,2Li} complex is almost stable., Comment: (5 pages, 4 figures)

Published
2012
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10. Performance of cardiovascular disease risk prediction equations in more than 14 000 survivors of cancer in New Zealand primary care: a validation study.

Author

Tawfiq, E, Selak, V, Elwood, JM, Pylypchuk, R, Tin, ST, Harwood, M, Grey, C, McKeage, M, Wells, S, Tawfiq, E, Selak, V, Elwood, JM, Pylypchuk, R, Tin, ST, Harwood, M, Grey, C, McKeage, M, and Wells, S

Abstract

BACKGROUND: People with cancer have an increased risk of cardiovascular disease. Risk prediction equations developed in New Zealand accurately predict 5-year cardiovascular disease risk in a general primary care population in the country. We assessed the performance of these equations for survivors of cancer in New Zealand. METHODS: For this validation study, patients aged 30-74 years from the PREDICT open cohort study, which was used to develop the New Zealand cardiovascular disease risk prediction equations, were included in the analysis if they had a primary diagnosis of invasive cancer at least 2 years before the date of the first cardiovascular disease risk assessment. The risk prediction equations are sex-specific and include the following predictors: age, ethnicity, socioeconomic deprivation index, family history of cardiovascular disease, smoking status, history of atrial fibrillation and diabetes, systolic blood pressure, total cholesterol to HDL cholesterol ratio, and preventive pharmacotherapy (blood-pressure-lowering, lipid-lowering, and antithrombotic drugs). Calibration was assessed by comparing the mean predicted 5-year cardiovascular disease risk, estimated using the risk prediction equations, with the observed risk across deciles of risk, for men and women, and according to the three clinical 5-year cardiovascular disease risk groups in New Zealand guidelines (<5%, 5% to <15%, and ≥15%). Discrimination was assessed by Harrell's C statistic. FINDINGS: 14 263 patients were included in the study. The mean age was 61 years (SD 9) for men and 60 years (SD 8) for women, with a median follow-up of 5·8 years for men and 5·7 years for women. The observed cardiovascular disease risk was underpredicted by a maximum of 2·5% in male and 3·2% in female decile groups. When patients were grouped according to clinical risk groups, observed cardiovascular disease risk was underpredicted by less than 2% in the lower risk groups and overpredicted by 2·2% for men and 3·

Published
2023

11. Peasants, patronage and taxation c.280-c.480

Author

Grey, C. A.

Subjects
930
Abstract

Relations between aristocratic landowners and agriculturalists in the late Roman period were part of systems of vertical alliance that were fluid, ambiguous and flexible. This thesis moves beyond theories of Patrocinium and the 'colonate of the late Roman Empire' to reconstruct those alliance systems. Three basic types of vertical interaction in rural contexts may be identified: tenancy, patronage and slavery. Peasants also interacted with aristocratic landowners in relations of casual or periodic labour, estate management and legal agency. It is argued that patronage for the purposes of tax evasion and registered tenancy were merely elements in these systems of vertical alliance. Chapter 1 addresses the attitudes of late Roman legislators and authors to patronage and registered tenancy through the language they employed in describing these phenomena. It will be demonstrated that these concepts continued to be analytically fluid, and did not crystallise into the institutions that have been labelled Patrocinium and the 'colonate' in the historiographical literature. In Chapter 2, late Roman rural labour relations are explored. It is argued that the analytical distinctions between the three categories of vertical alliance identified above mask a reality of blurred boundaries and elision of various relationships of dependence. In Chapter 3, those systems of vertical alliance are further contextualised within the social and economic world of the fourth and fifth centuries. It is argued that that world was characterised by 'landscapes of diversity', within which particular systems of interaction between peasants and aristocrats were necessarily adaptable and disparate. Those systems of interaction complemented and competed with patterns of horizontal organisation within individual rural communities, and between communities. It is upon these patterns of competition and complementarity that the tax system of the late Roman period was imposed in the late third century. Chapter 4 focuses upon the tax system, and the elements of it that contributed to the high visibility of structures of rural social organisation in the period.

Published
2000

20. Clinical outcomes and gestational age based prediction of pneumatosis intestinalis in preterm infants with necrotizing enterocolitis.

Author

Garg, P.M., Paschal, J.L., Ansari, M.A.Y., Sonani, H., Grey, C., Chan, S., Varshney, N., and Hillegass, W.

Subjects
PREMATURE infants, GESTATIONAL age, ENTEROCOLITIS, BIRTH weight, TREATMENT effectiveness
Abstract

BACKGROUND: To determine the clinical implications and gestation age-specific diagnostic predictability of pneumatosis in preterm infants with necrotizing enterocolitis (NEC). METHODS: A retrospective study on abdominal radiographs comparing clinical and radiological information in infants with and without pneumatosis. RESULT: Our findings disproved our hypothesis. Pneumatosis was seen more frequently in infants with higher gestational age [28.4 (26.1–32.4) vs. 26.4 (24.3–29) weeks; p < 0.001] and birth weight [1110 (762–1768) vs. 770 (645–1022) grams; p < 0.001] and were more likely delivered vaginally (39.1% vs. 21.7%, p = 0.01). Portal venous gas was seen frequently on radiographs (10.3% vs. 0%, p < 0.001), but not pneumoperitoneum (20.7% vs. 36.7%, p = 0.02). Infants with pneumatosis frequently developed acute kidney injury, with higher serum creatinine (16.5% vs. 4.5%, p = 0.02) and frequent oliguria (12.9% vs. 2.7 %; p = 0.043) and had higher C-reactive protein levels at 24 and 96 hours (p < 0.002). Receiver operating curves for pneumatosis showed GA >28 weeks and birth weight > 1000 gm to have a sensitivity of 58.6% and specificity of 72.5%. CONCLUSION: Contrary to our hypothesis, infants who developed pneumatosis during NEC were more mature with a higher gestational age and birth weight than those who did not. [ABSTRACT FROM AUTHOR]

Published
2022
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21. Clinical Utility of Random Anti–Tumor Necrosis Factor Drug–Level Testing and Measurement of Antidrug Antibodies on the Long-Term Treatment Response in Rheumatoid Arthritis

Author

Jani, Meghna, Chinoy, Hector, Warren, Richard B., Griffiths, Christopher E. M., Plant, Darren, Fu, Bo, Morgan, Ann W., Wilson, Anthony G., Isaacs, John D., Hyrich, Kimme L., Barton, Anne, Prouse, P. J., Moitra, R. K., Shawe, D. J., Nisar, M., Fairburn, K., Nixon, J., Barnes, T., Hui, M., Coady, D., Wright, D., Morley, C., Raftery, G., Bracewell, C., Bridges, M., Armstrong, D., Chuck, A. J., Hailwood, S., Kumar, N., Ashok, D., Reece, R., OʼReilly, S. C., Ding, T., Badcock, L. J., Deighton, C. M., Raj, N., Regan, M. R., Summers, G. D., Williams, R. A., Lambert, J. R., Stevens, R., Wilkinson, C., Kelly, C. A., Hamilton, J., Heycock, C. R., Saravanan, V., Cope, A., Garrood, T., Ng, N., Kirkham, B., Green, M., Gough, A., Lawson, C., Das, D., Borbas, E., Wazir, T., Emery, P., Bingham, S., Bird, H. A., Conaghan, P. G., Pease, C. T., Wakefield, R. J., Buch, M., Bruce, I., Gorodkin, R., Ho, P., Parker, B., Smith, W., Jenkins, E., Mukhtyar, C., Gaffney, K., Macgregor, A. J., Marshall, T., Merry, P., DeSilva, C., Birrell, F. N., Crook, P. R., Szebenyi, B., Bates, D., James, D., Gillott, T., Alvi, A., Grey, C., Browning, J., McHale, J. F., Gaywood, I. C., Jones, A. C., Lanyon, P., Pande, I., Doherty, M., Gupta, A., Courtney, P. A., Srikanth, A., Abhishek, A., Das, L., Pattrick, M., Snowden, H. N., Bowden, A. P., Smith, E. E., Klimiuk, P., Speden, D. J., Naz, S., Ledingham, J. M., Hull, R. G., McCrae, F., Cooper, A., Young-Min, S. A., Wong, E., Shaban, R., Woolf, A. D., Davis, M., Hutchinson, D., Endean, A., Mewar, D., Tunn, E. J., Nelson, K., Kennedy, T. D., Dubois, C., Pauling, J., Korendowych, E., Jenkinson, T., Sengupta, R., Bhalla, A., McHugh, N., OʼNeil, T., Herrick, A. L., Jones, A. K., Cooper, R. G., Dixon, W. G., Harrison, B., Buckley, C. D., Carruthers, D. C., Elamanchi, R., Gordon, P. C., Grindulis, K. A., Khattak, F., Raza, K., Situnayake, K., Akil, M., Till, S., Dunkley, L., Tattersall, R., Kilding, R., Tait, T., Maxwell, J., Kuet, K.-P., Plant, M. J., Clarke, F., Fordham, J. N., Tuck, S., Pathare, S. K., Paul, A., Marguerie, C. P., Rigby, S. P., Dunn, N., Abbas, I., Filer, C., Abernethy, V. E., Clewes, A. R., Dawson, J. K., Kitas, G., Erb, N., Klocke, R., Whallett, A. J., Douglas, K., Pace, A., Sandhu, R., John, H., Shand, L., Lane, S., Foster, H., Griffiths, B., Griffiths, I., Kay, L., Ng, W.-F., Platt, P. N., Walker, D. J., Peterson, P., Lorenzi, A., Friswell, M., Thompson, B., Lee, M., Pratt, A., Hopkinson, N. D., Dunne, C. A., Quilty, B., Marks, J., Mukherjee, S., Mulherin, D., Chalam, S. V., Price, T., Sheeran, T., Venkatachalam, S., Baskar, S., Al-Allaf, W., McKenna, F., Shah, P., Filer, A., Bowman, S. J., Jobanputra, P., Rankin, E. C., Allen, M., Chaudhuri, K., Dubey, S., Price-Forbes, A., Ravindran, J., Samanta, A., Sheldon, P., Hassan, W., Francis, J., Kinder, A., Neame, R., Moorthy, A., Bukhari, M., Ottewell, L., Palkonyai, E., Hider, S., Hassell, A., Menon, A., Dowson, C., Kamath, S., Packham, J., Dutta, S., Price, S., Roddy, E., Paskins, Z., OʼReilly, D. T., Rajagopal, V., Bhagat, S., Chattopadhyay, C. B., Quinn, D., Isdale, A., Brown, A., Saleem, B., Foo, B., Al Saffar, Z., and Koduri, G.

Published
2015
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25. Valve Timing and Area Profile Selection for Hydraulic Pumps and Motors

Author

James D. Van de Ven, Thomas R. Chase, and Grey C. Boyce-Erickson

Subjects
Valve timing, Reliability (semiconductor), Environmental science, Hydraulic pump, Selection (genetic algorithm), Automotive engineering
Abstract

A significant amount of research has been conducted to select valve timing and area profiles that create efficient and quiet hydraulic pumps and motors. Numerous active valve architectures have been modeled and optimized, but the rationale for the final solution is often unclear. The solution is usually highly dependent on the modeled valve geometry constraints and the duty cycle of the pump or motor for which the valve was optimized. In contrast, this paper proposes a methodology for designing efficient valving that is not constrained to any specific valve geometry, operating point, parameterization, or physical system limitation. An idealized valve area profile is formulated using a piston-cylinder model with variable valve openings. A working fluid that has a pressure dependent bulk modulus is utilized in the model. The valve timing is idealized by constraining it to produce a specified constant pressure drop across the valve. The idealized area profile is synthesized by modeling the piston-cylinder as a pump with passive (check) valves. A representation of the idealized timing is demonstrated for positive pressure differential and positive rotation direction, also known as the first quadrant. The effect of varying pressure on valve timing is shown for the first quadrant, but the trend can be extrapolated for all quadrants of operation. The idealized valve area profile is implemented as fixed valve timing in a pump-motor, meaning the valve area is only a function of the timing angle of the rotating group. Fixed valve timing is preferred to variable valve timing as it can often be implemented mechanically, increasing reliability. The pump-motor is simulated in one rotation direction through a pressure range. Performance is high in pumping operation, but when the pressure differential is reversed, cylinder pressure spikes ensue. Two strategies to modify an idealized valve area profile are presented: timing grooves and a pressure shifted valve timing. Timing grooves reduce pressure spikes and cavitation in the cylinder but generally increase throttling losses. A pressure shifted valve timing has lower throttling energy losses, making it the favored solution.

Published
2020

26. Mechanical and Hydraulic Actuation Strategies for Mainstage Spool Valves in Hydraulic Motors

Author

James D. Van de Ven, Nathaniel J. Fulbright, Thomas R. Chase, Perry Y. Li, John A. Voth, and Grey C. Boyce-Erickson

Subjects
Materials science, Hydraulic motor, Dynamic models, Compressibility, Mechanical engineering, Engineering simulation, Leakage (electronics)
Abstract

A large variety of options for the internal valves of a hydraulic motor are available. Poppet valves, rotary valves, and port plates are common options, but each have drawbacks such as actuation force, complexity, leakage, or friction. An alternative type that is also common is spool valves. Spool valves require minimal actuation force and have low throttling losses if sized correctly. This paper compares two drive options for a mainstage spool valve: a hydraulic pilot from a rotary valve and mechanical actuation. Dynamic models of the two valve configurations are created to carry out design studies and evaluate the performance of the motor. Compressibility effects, viscous drag, and flow forces are included in the model. Simulations show that the rotary valve pilot operation causes an unacceptable lag in the motion of the spool that cannot be corrected without reducing performance when running in reverse. Furthermore, the rotary pilot stage drive results in the motor timing becoming retarded at higher operating speeds. For these reasons, mechanically actuated valves are preferred over pilot operated valves for hydraulic motors operated bi-directionally or across a wide speed range.

Published
2019

27. Automated Design and Analysis of a Variable Displacement Linkage Motor

Author

Grey C. Boyce-Erickson, Perry Y. Li, Thomas R. Chase, James D. Van de Ven, and Nathaniel J. Fulbright

Subjects
Control theory, law, Computer science, Torque, Displacement (orthopedic surgery), Linkage (mechanical), Variable displacement, law.invention
Abstract

Hydrostatic drives consisting of a variable displacement pump and a low speed high torque (LSHT) motor are frequently used in off-highway vehicles. A variable displacement traction motor is desirable because of the ability to downsize the pump and thereby run the hydrostat at higher efficiency, as well as the possibility of hybridization of the drivetrain. Currently on the market are fixed and discrete speed LSHT radial piston motors and high speed low torque variable displacement axial piston motors. The radial piston motors are displacement dense but are not continuously variable, whereas the axial piston motors are continuously variable but require gearboxes, introducing packaging and robustness concerns. The Variable Displacement Linkage Motor (VDLM) is a LSHT motor that is continuously variable. It offers several benefits over current LSHT motors in that it is highly efficient over its operating range, it has low torque ripple, and it is displacement dense due to its multi-lobed cam and radial packaging. As with the design of any motor, the process is iterative and must be performed whenever performance objectives change. This paper describes an automated method for rapid exploration of the solution space for a variable displacement motor with specific application to the VDLM. This method leads to a motor design that theoretically can achieve 97% efficiency with a torque ripple below 5% at full displacement.

Published
2019

29. Infrared-active optical phonons in LiFePO4 single crystals.

Author

Stanislavchuk, T. N., Middlemiss, D. S., Syzdek, J. S., Janssen, Y., Basistyy, R., Sirenko, A. A., Khalifah, P. G., Grey, C. P., and Kostecki, R.

Subjects
PHONONS, OLIVINE, IRON silicates, ELLIPSOMETRY, DENSITY functional theory
Abstract

Infrared-active optical phonons were studied in olivine LiFePO4 oriented single crystals by means of both rotating analyzer and rotating compensator spectroscopic ellipsometry in the spectral range between 50 and 1400 cm-1. The eigenfrequencies, oscillator strengths, and broadenings of the phonon modes were determined from fits of the anisotropic harmonic oscillator model to the data. Optical phonons in a heterosite FePO4 crystal were measured from the delithiated ab-surface of the LiFePO4 crystal and compared with the phonon modes of the latter. Good agreement was found between experimental data and the results of solid-state hybrid density functional theory calculations for the phonon modes in both LiFePO4 and FePO4. [ABSTRACT FROM AUTHOR]

Published
2017
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44. Long-term low ascorbic acid intake reduces bone mass in guinea pigs

Author

Kipp, Deborah E., Grey, C. Eric, McElvain, Michele E., Kimmel, Donald B., Robinson, Ralph G., and Lukert, Barbara P.

Subjects
Guinea pigs -- Physiological aspects, Vitamin C in animal nutrition -- Research, Bone densitometry -- Research, Food/cooking/nutrition
Abstract

The effect of long-term (1 y) low to excess ascorbic acid (AA) intake on bone mass was evaluated using guinea pigs that were 12-14 d old at the start of the experiment. Dietary AA was low (0.15 g/kg diet) (n = 7), normal (0.50 g/kg) (n = 8) or excess (10 g/kg) (n = 8). After 12 mo, total body bone mineral density (BMD, mg/[cm.sup.2]) and bone mineral content (BMC, g) were determined by dual energy X-ray absorptiometry. Histomorphometric analysis of the cancellous bone of the proximal tibial metaphysis was completed after in vivo dual fluorochrome labeling. Total body BMD of the low AA group was 4.9% lower (P [less than] 0.05), and total body BMC was 12.4% lower (P [less than] 0.05) than in the normal AA group. Total body BMD and BMC were similar in normal and excess AA groups and in the low and excess AA groups. Histomorphometric analysis indicated significantly greater (P [less than] 0.05) double-labeled bone surface, mineralizing surface, and bone formation rate in the low AA guinea pigs compared with the normal AA animals. Thus, there was greater bone turnover in the low AA group than in the normal AA guinea pigs. No differences in histomorphometric endpoints existed between the normal AA and excess AA groups. Long-term AA deficiency, during the period of rapid growth and slower phases of skeletal maturation, resulted in bone abnormalities in adult guinea pig skeletons. Long-term dietary AA excess caused no such abnormalities. J. Nutr. 126: 2044-2049, 1996. INDEXING KEY WORDS: guinea pigs; ascorbic acid; bone mass; densitometry; histomorphometry

Published
1996

45. Equilibrio, cinética y termodinámica de la adsorción del colorante DB-86 sobre carbón activado de la cáscara de yuca

Author

Castellar Ortega, Grey C., Mendoza-Colina, Evert de Jesús, Angulo M, Edgardo, Paula P., Zilena, Rosso B., María, Jaramillo Colpas, Javier Enrique, Castellar Ortega, Grey C., Mendoza-Colina, Evert de Jesús, Angulo M, Edgardo, Paula P., Zilena, Rosso B., María, and Jaramillo Colpas, Javier Enrique

Abstract

Objective. To establish by means of experimenting by batch the capacity of removal, the kinetics and adsorption thermodynamics of activated carbon prepared from manioc husk (Manihot esculenta) in the removal of direct blue 86 dye. Materials and methods. Firstly, the experimental methodology worked on the preparation of activated carbon by chemical activation of manioc husk with H3PO4 calcined at 530°C. In the characterization the texture properties were determined by means of the blue methylene and iodine indices, the basic and acidic functional groups were quantified by the Boehm method, and the proximate analyses were done following the norms ASTM D2867-70, ASTM D2866 and ASTM D2866-94. During the batch studies, the effect of several parameters over the adsorption capacity was evaluated: pH (2, 4, 8 and 10), temperature (25, 30 and 40°C) and initial concentration of the dye (20, 40, 60, 80 and 100 mg/L). Both physicochemical and adsorption characteristics of the activated carbon from manioc husk (CAY) were compared against those of a commercial brand (CAM). Results. The results of characterization showed that both carbons have a chemistry heterogeneous surface, acidic for CAY and basic for CAM. The maximum capacity obtained was 6.1 mg/g for CAY and 3.7 mg/g for CAM. The thermodynamic calculations showed that the removal was spontaneous. The kinetics for both carbon samples fits a pseudo second-order model. Conclusions. The activated carbon obtained from the manioc husk can be considered an efficient adsorbent for the removal of dyes., RESUMEN Objetivo. Establecer mediante experimentos por lote la capacidad de remoción, la cinética y termodinámica de adsorción del carbón activado preparado a partir de la cáscara de yuca (Manihot esculenta) en la remoción del colorante azul directo 86. Materiales y métodos. La metodología experimental consistió inicialmente en la preparación del carbón activado por activación química de la cáscara de yuca con H3PO4 y su posterior calcinación a 530°C. En la caracterización se determinaron las propiedades de textura mediante el índice de yodo e índice de azul de metileno, se cuantificaron los grupos funcionales orgánicos ácidos y básicos con el método Boehm, y se realizó el análisis próximo siguiendo las normas ASTM D-2867-70, ASTM D2866 y ASTM D2866-94. En el estudio por lote, el efecto de varios parámetros sobre la capacidad de adsorción fueron evaluados: el pH (2, 4, 8 y 10), la temperatura (25, 30 y 40°C) y la concentración inicial de colorante (20, 40, 60, 80 y 100 mg/L). Tanto las características fisicoquímicas como los ensayos de adsorción del carbón activado preparado a partir de la cáscara de yuca (CAY) fueron comparadas con otro de marca comercial (CAM). Resultados. Los resultados de la caracterización indican que ambos carbones tienen una química de superfície heterogénea, de naturaleza ácida para el CAY y básica para el CAM. La máxima capacidad obtenida fue 6.1 mg/g para el CAY y de 3.7 mg/g para el CAM. Los cálculos termodinámicos indican que la remoción es espontánea y para ambos carbones la cinética se ajusta al modelo de pseudo segundo orden. Conclusiones. El carbón activado obtenido a partir de la cáscara de yuca puede considerarse un adsorbente eficiente en la remoción de colorantes.

Published
2019

46. Solar radiation in Jamaica

Author

Chen, A.A., Chin, P.N., Forrest, W., McLean, P., and Grey, C.

Subjects
Jamaica -- Energy use, Solar radiation -- Research, Earth sciences, Petroleum, energy and mining industries
Abstract

Average monthly global radiation in Jamaica was calculated for the years between 1978 and 1987 from values measured at 12 stations and from Angstrom-coefficient derived values. From these values daily global radiation was estimated for various periods at grid points separated by approximately 10 km on a square. Three dimensional plots and contour maps for the various periods were produced. The interpolation was based on kriging adopted by Hay (1986). A relationship between global and diffuse radiation based on the Liu and Jordan (1960) relationship was obtained. The errors in the interpolated annual values were less than 10%. The maps were made available to the public with suggested usages of solar energy. Diffuse radiation formed less than 50% of the total radiation.

Published
1994

47. Effect of piperacillin-tazobactam vs meropenem on 30-day mortality for patients with e coli or Klebsiella pneumoniae bloodstream infection and ceftriaxone resistance

Author

Harris, P. N. A., Tambyah, P. A., Lye, D. C., Mo, Y., Lee, T. H., Yilmaz, M., Alenazi, T. H., Arabi, Y., Falcone, M., Bassetti, M., Righi, E., Rogers, B. A., Kanj, S., Bhally, H., Iredell, J., Mendelson, M., Boyles, T. H., Looke, D., Miyakis, S., Walls, G., Al Khamis, M., Zikri, A., Crowe, A., Ingram, P., Daneman, N., Griffin, P., Athan, E., Lorenc, P., Baker, P., Roberts, L., Beatson, S. A., Peleg, A. Y., Harris-Brown, T., Paterson, D. L., Mcnamara, J., Sieler, R., Garlick, J., Costa, J., Roney, J., Pratt, N., Tabaja, H., Kmeid, J., Tayyar, R., El Zein, S., Jones, S., Cowan, R., Tai, A., Lin, B., Rad, B., Macmorran, E., Pollard, J., Dinleyici, R., Istanbullu, A., Ceylan, B., Mert, A., Hashhoush, M., Dalwi, T., Korman, T., Azzam, R., Birrell, M., Hughes, C., Khan, S., Lau, J., Lee, L., Lim, K., Lin, Y. D., Lister, D., New, D., Rafiei, N., Stewart, J., Trad, M. A., Aye Yeung, V., Mcbride, S., Holland, D., Hopkins, C., Luey, C., Taylor, S., Morpeth, S., Finney, M., Martin, M., Holland, U., Ali, J., Jureen, R., Underwood, N., Henderson, A., Runnegar, N., Slavin, M., Robinson, O., Rishu, A., Shawkat, S., Fish, J., Chin Liew, K., Newton, P., Merelli, M., Carnelutti, A., Ussai, S., Pecori, D., Izharuddin, E., Young, B., Ding, Y., Ram, R., Kelly, J., Joshi, N., Richards, G., Smith, O., Alli, A., Vermeulen, I., Wright, B., Grey, C., Stewart, A., Reddy, D., Wasserman, S., Richi, H., Sultana, K., Alanazi, N., Bin Awad, E., Franzetti, F., Stolz, A., De Kock, E., Magongoa, T., Dutoit, M., Russo, A., Dentone, C., Eisen, D., and Heyer, L.

Subjects
Adult, Male, Piperacillin, Tazobactam Drug Combination, Ceftriaxone, Drug Resistance, Bacterial, Penicillanic Acid, Bacteremia, Meropenem, Middle Aged, Anti-Bacterial Agents, Klebsiella Infections, Klebsiella pneumoniae, Cause of Death, Escherichia coli, Humans, Female, Thienamycins, Aged, Drug Resistance, Bacterial, Escherichia coli Infections, Piperacillin, Tazobactam Drug Combination
Published
2018

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