154 results on '"Schwegler E"'
Search Results
52. Conformational dynamics of the dimethyl phosphate anion in solution
- Author
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Schwegler, E., Galli, G., and Gygi, F.
- Published
- 2001
- Full Text
- View/download PDF
53. EFEITO DO JEJUM E DA ADMINISTRAÇÃO DE INSULINA SOBRE OS PARÂMETROS METABÓLICOS DE OVELHAS EM CONFINAMENTO.
- Author
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SCHNEIDER, A., SCHWEGLER, E., GOULART, M. A., ROOS, T. B., RABASSA, V. R., DEL PINO, F. A. B., and CORRÊA, M. N.
- Published
- 2007
54. Milk composition, ruminal ph and metabolic parameters of dairy cows supplemented with slow-release urea,Composição do leite, pH do fluído ruminal e perfil metabólico de vacas leiteiras suplementadas com uréia de liberação lenta
- Author
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Goulart, M. A., Montagner, P., Lopes, M. S., Azambuja, R. C. C., Schwegler, E., Antunes, M. M., Pereira, R. A., Roll, V. F. B., Augusto Schneider, Rabassa, V. R., Del Pino, F. A. B., and Corrêa, M. N.
55. Monensin controlled-release capsules do not change performance and metabolic profile in unchallenged beef cattle
- Author
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Demarco, C. F., Schwegler, E., Brauner, C. C., Ferri, E., Jéssica Halfen, Florio, G., Florio, D., Da Silva Pedroso, C. E., Gonçalves, F. M., and Corrêa, M. N.
56. Calcium and insulin correlation during the glucose tolerance test in pregnant non-pregnant ewes
- Author
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Schmitt, E., Augusto Schneider, Goulart, M. A., Schwegler, E., Pereira, R. A., Hoffmann, D. A. C., Lopes, M. S., Hax, L. T., Del Pino, F. A. B., and Correa, M. N.
- Subjects
insulin ,gestação ,teste de tolerância ,insulina ,glucose tolerance test ,pregnancy ,glicose ,ovelha ,ewe - Abstract
Compararam-se as concentrações de cálcio, glicose e insulina em ovelhas gestantes e não gestantes submetidas ao teste de tolerância à glicose (TTG). Oito ovelhas gestantes (GG) e oito não gestantes (NG) foram submetidas ao TTG por meio da administração endovenosa de uma solução de glicose, na dose de 500mg/kg de peso vivo. Amostras de sangue foram coletadas nos tempos de -15, zero, 15, 30, 45, 60, 90, 120, 150 e 180 minutos, sendo zero min o momento da infusão, para avaliação da concentração sanguínea de glicose, cálcio e insulina. Foi avaliada a taxa de metabolização de glicose e insulina, por meio do cálculo da área sob a curva (ASC). As concentrações de glicose, cálcio, insulina e a ASC da insulina não diferiram entre os grupos (P>0,05), entretanto as três últimas ASCs da glicose foram mais elevados nas gestantes (P
57. Comment on 'Dissociation of water under pressure' (multiple letters)
- Author
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Dellago, C., Geissler, P. L., Chandler, D., Juerg Hutter, Parrinello, M., Schwegler, E. R., Galli, G., Gygi, F., and Hood, R. Q.
58. Molecular dynamics simulations and X-ray emission studies of Mg2+ cation in liquid water.
- Author
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Kashtanov, Stepan, Schwegler, E., Galli, G., Guo, J.-H., Luo, Yi, Kashtanov, Stepan, Schwegler, E., Galli, G., Guo, J.-H., and Luo, Yi
- Abstract
QC 20101101
59. EFEITO DA ZEARALENONA SOBRE PARÂMETROS METABÓLICOS DE BORREGAS.
- Author
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RABASSA, V. R., SCHWEGLER, E., GOULART, M. A., LISBOA, F. P., HOFFMANN, D. A. C., MADEIRA, E. M., DA SILVA NETO, J. W., FONSECA, M. C. P., ROLL, V. F. B., and CORRÊA, M. N.
- Published
- 2007
60. Recurrence relations for calculation of the Cartesian multipole tensor
- Author
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Challacombe, M., Schwegler, E., and Almloef, J.
- Published
- 1995
- Full Text
- View/download PDF
61. Ab-initio modeling of water-semiconductor interfaces for direct solar-to-chemical energy conversion
- Author
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Schwegler, E
- Published
- 2010
62. Hydrogen-Helium Mixtures at High Pressure
- Author
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Schwegler, E
- Published
- 2012
63. Local Structural Models of Complex Oxygen- and Hydroxyl-rich GaP/InP(001) Surfaces
- Author
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Schwegler, E
- Published
- 2011
64. STRUCTURE AND REACTIVITY OF III-V SEMICONDUCTORS FOR PHOTOELECTROCHEMICAL HYDROGEN PRODUCTION
- Author
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Schwegler, E
- Published
- 2010
65. First-Principles Simulations of Aqueous Solutions
- Author
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Schwegler, E
- Published
- 2007
- Full Text
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66. CALCULATION OF REVERSE ANNEALING IN NEUTRON-DAMAGED p-TYPE SILICON.
- Author
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Schwegler, E
- Published
- 1971
- Full Text
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67. Effects of dietary supplementation with inactivated Lactobacillus plantarum on growth performance, haemato-biochemical parameters, liver fatty acids profile and intestinal microbiome of Nile tilapia.
- Author
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Ferro PHS, Ribeiro GC, Borba LE, Batista RO, da Rosa Farias D, Fracalossi DM, Schwegler E, Owatari MS, and Schleder DD
- Subjects
- Animals, Lactobacillus plantarum, Gastrointestinal Microbiome drug effects, Cichlids, Animal Feed analysis, Probiotics pharmacology, Probiotics administration & dosage, Dietary Supplements analysis, Fatty Acids analysis, Diet veterinary, Liver drug effects, Liver metabolism
- Abstract
This study investigated the effects of dietary supplementation with inactivated Lactobacillus plantarum for Nile tilapia (Oreochromis niloticus). Three treatments, in quintuplicate, were established: a control group, fish fed a diet without additives; LP group, fish fed a diet supplemented with live probiotic; and IP group, fish fed a diet supplemented with inactivated probiotic. Final weights (49.40 ± 3.15 g) and weight gains (38.20 ± 3.23 g) were increased in tilapia in the IP group. Feed conversion (1.32 ± 0.04) decreased significantly in the IP group. Haemato-biochemical parameters were significantly influenced by dietary supplementation. Erythrocyte count (262.74 ± 69.28 × 106 μL
-1 ) was significantly low, while albumin (1.79 ± 1.12 g dL-1 ) and cholesterol (254.14 ± 98.49 mg dL-1 ) were high in the control group. Dietary supplementation modified the tilapia microbiome. Rhodobacter was abundant in fish intestines from the control and IP groups. Phreatobacter was abundant in the IP and LP groups, while Aurantimicrobium and Bosea were abundant in the LP group. Oleic acid (C18:1n9) was significantly increased in the LP (3.25 ± 0.49%) and IP (3.02 ± 0.30%) groups. Hexadecatrienoic acid (C16:3n4) was significantly increased (0.04 ± 0.01%) in the IP group, while Cis 11,14,17-eicosatrienoic acid (C20:3n3) (0.31 ± 0.03%) and adrenic acid (C22:4n6) (0.11 ± 0.02%) were significantly decreased in the LP group. Additionally, monounsaturated fatty acids (MUFA) were significantly increased (4.83 ± 0.35%) in the LP group compared to that in the control group. Collectively, these results indicate the potential of inactivated L. plantarum for use in commercial feed, leading to the conclusion that both inactivated and live L. plantarum can improve the Nile tilapia metabolism, altering haematological and biochemical markers., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)- Published
- 2024
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68. Effect of Density and Lineage on Dorsal Surface Temperature, Performance, and Carcass Condemnation of Broiler Grillers.
- Author
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Marins IC, Giacomelli B, Correia B, Olsson DC, Moreira F, de Oliveira Júnior JM, Bianchi I, Schwegler E, Tanure CB, Quirino M, Paim TDP, Fonseca NN, Santos BRCD, and Peripolli V
- Abstract
The aims of this study were (i) to evaluate the effect of density, lineage, age, and time of day on dorsal surface temperature and (ii) to evaluate the effect of density and lineage on performance and carcass condemnations in broiler grillers. The evaluations were carried out in barns with the Dark House system, with two densities, 17 and 19 chickens/m
2 and two lineages, Cobb and Ross. The dorsal surface temperature of the chickens was measured by infrared thermography at 7, 14, 21, 23, 25 and 27 days of age, four times a day. The average daily weight gain, feed conversion, mortality, partial carcass condemnations, as well as those due to arthritis and dermatosis were also evaluated. The highest dorsal surface temperatures were observed in Cobbs housed at a density of 17 chickens/m2 , and in Ross housed at a density of 19 chickens/m2 . Cobbs housed at a 17 chickens/m2 density showed the lowest feed conversion compared to Ross at the same density. Ross showed higher dorsal surface temperatures when compared to Cobbs at 14, 21, and 27 days. Cobbs showed higher percentages of partial carcass condemnation and arthritis compared to Ross. The higher density of broiler grillers in the Dark House system does not influence the dorsal surface temperature, performance, dermatosis, arthritis, and partial carcass condemnations.- Published
- 2024
- Full Text
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69. Metabolic and productive parameters of lactating dairy cows under heat stress conditions supplemented with plant polyphenol extract.
- Author
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Stingelin LA, Schell CE, Palmeira M, Araujo GM, Casas BAD, Moreira F, Alvarado-Rincón JA, Schneider A, Peripolli V, and Schwegler E
- Subjects
- Animals, Cattle physiology, Female, Plant Extracts administration & dosage, Plant Extracts pharmacology, Heat-Shock Response drug effects, Hot Temperature, Lactation drug effects, Dietary Supplements analysis, Milk chemistry, Animal Feed analysis, Diet veterinary, Polyphenols administration & dosage, Polyphenols pharmacology, Polyphenols analysis
- Abstract
The impact of heat stress on dairy cattle leads to significant economic losses and a negative impact on the welfare of the animals. The objective of this research was to evaluate the effect of the nutritional additive (Thermoplus®) in dairy cows under postpartum heat stress conditions, and its effects on the metabolic profile, production and quality of milk. Eighteen lactating Holstein cows (8 multiparous and ten primiparous), in a free-stall system, with a mean body condition score (BCS) of 3.14 ± 0.05, live weight of 624.55 ± 18, 61 kg, with initial mean days in milk (DIM) of 90 ± 10.11, were selected. The animals were grouped into a control (CG, n = 9) and a treatment (TG, n = 9). Both groups underwent 14 days of diet adaptation, the TG received the basal diet supplemented with 50 g of the additive, once a day, individually, while the control group received only the total diet. Data collection of metabolic and productive parameters were evaluated on days -14 (before adaptation), 1 (after the diet adaptation period), 16, 30, and 44. Milk, blood, and body condition score (BCS) were collected once a day, and heart rate, respiratory rate, and rectal temperature were collected twice a day. Serum concentrations of albumin, calcium, magnesium, glucose, gamma-glutamyl transferase (GGT), beta-hydroxybutyrate (BHBA), non-esterified fatty acids (NEFAs), and paraoxonase-1 (PON-1) were evaluated. In the milk, the percentage of fat, protein, lactose, and total solids were determined in each sampling. Milk yield was measured daily. Humidity and ambient temperature values were collected on the days of the collection every 30 min, from 5:30 am to 5:00 pm, to calculate the temperature-humidity index (THI). Statistical analyzes were performed using the SAS software (version 9.3, SAS Institute Inc., Cary, NC, USA). The THI ranged from 62.22 to 79.47. Our findings showed that when the THI was greater than 72, the animals in the TG were able to maintain milk yield (Odds ratio (OD) = -0.0577,), and the animals in the CG had a greater chance of reducing it (OD = -0.2301). Multiparous cows in the TG had higher milk yield than CG (32.57 ± 0.34 vs 30.50 ± 0.36 kg per day; P = 0.0078) and lower SCC (34.110 ± 6,940 vs 665.50 ± 214.41 cells per ml; P = 0.03), with the same percentages of total solids (P > 0.05). In multiparous metabolic markers, TG when compared CG had higher albumin concentrations (2.50 ± 0.07 vs 2.12 ± 0.07 g/dl; < 0.001), equal PON-1 (P > 0.05), and higher BHBA levels (0.49 ± 0.03 vs 0.39 ± 0.04 mmol/l). Primiparous from the CG had higher concentrations of NEFA (0.18 ± 0.02 mmol/l) than multiparous from the same group (0.09 ± 0.02 mmol/l) P = 0.0265. The use of the plant polyphenol extract in postpartum Holstein cows challenged by heat stress had beneficial effects on the production and health of the mammary gland in multiparous cows without decreasing milk solids. The non-reduction of the activities of the acute phase proteins indicates an immunomodulatory and inflammatory-reducing effect of the product used., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)
- Published
- 2024
- Full Text
- View/download PDF
70. Strategies to alleviate heat stress on performance and physiological parameters in feedlot-finished cattle under heat stress conditions. A systematic review-meta-analysis.
- Author
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Azevedo LA, Canozzi MEA, Rodhermel JCB, Schwegler E, La Manna A, Clariget J, Bianchi I, Moreira F, Olsson DC, and Peripolli V
- Subjects
- Cattle, Animals, Heat-Shock Response, Respiratory Rate, Sunlight, Animal Feed analysis, Diet veterinary, Climate, Heat Stress Disorders prevention & control, Heat Stress Disorders veterinary
- Abstract
Strategies to alleviate heat stress on live performance - dry matter intake (DMI), average daily gain (ADG), and feed conversion efficiency (FCE) - and on physiological parameters - respiratory rate (RR) and panting score (PS) - of feedlot-finished cattle were evaluated by systematic review-meta-analysis. Using the PICO framework were identified 3813 records, with 31 publications and 6729 cattle being considered in the meta-analysis (MA). The comparison most reported was sun vs. shade (n = 24 publications), followed by shade vs. shade (area per animal and effectivity in reduce solar load) (n = 7 publications) and sun vs. sprinkling (n = 4 publications). Cattle with access to shade with total reduction in solar load improved ADG (p = 0.008) and FCE (p = 0.024), and reduced RR (p < 0.001) compared to unshaded animals. Cattle with access to shade with a height between 3 and 4 m increased ADG (p < 0.001), tended to improve FCE (p = 0.054), and reduced RR (p < 0.001) compared to unshaded animals. An area of shade from 2 to 4 m
2 /animal increased ADG (p = 0.002), and higher than 4 m2 /animal reduced RR (p < 0.001) compared to unshaded animals. Animals that received sprinkling volume below 1 L/animal/min improved ADG (p = 0.008) compared to unshaded animals. Cattle with access to shade with a high area per animal improved DMI (p = 0.023) and ADG (p < 0.001) compared to animals with a low area. In univariate meta-regression, it was observed that the variables significantly (P < 0.05) influencing DMI were THI category; influencing ADG were cattle gender, THI category, and coat color; influencing FCE were cattle age and hemisphere; and influencing RR were country, THI category and climate. Performance and physiological parameters of feedlot-finished cattle under heat stress depend on animal and environmental characteristics., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)- Published
- 2024
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71. Gender-specific differences in comorbidities, in-hospital complications and outcomes in emergency patients with ethanol intoxication with and without multisubstance use.
- Author
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Schwegler E, Bachmann M, Kube F, and Eriksson U
- Subjects
- Humans, Male, Female, Ethanol, Sex Factors, Retrospective Studies, Hospitals, Emergency Service, Hospital, Alcoholic Intoxication epidemiology, Substance-Related Disorders epidemiology, Substance-Related Disorders therapy
- Abstract
Aims of the Study: To analyse gender-specific differences in comorbidities, multisubstance abuse, in-hospital complications, intensive care unit transfers and referrals to psychiatric wards of emergency department patients with ethanol intoxication. Several lines of evidence suggest an influence of gender differences on diagnostic and therapeutic approaches to various diseases., Methods: Over a period of 7 years, all patients with signs or symptoms of ethanol intoxication and a positive blood ethanol test admitted for the first time to the emergency department of a Swiss regional tertiary referral hospital were prospectively enrolled. Patients were categorised into two subgroups: patients without additional drug use were considered ethanol-only cases, whereas patients who had also ingested other substances (as determined from bystanders, physicians and urine drug screening) were considered multisubstance cases. A retrospective analysis of this database evaluated gender-specific differences in comorbidities, multisubstance abuse, in-hospital complications, intensive care unit transfers and referrals to psychiatric wards within these two subgroups. Statistical analysis included Fisher's exact test for categorical data and Wilcoxon rank sum test for continuous data., Results: Of 409 enrolled patients, 236 cases were ethanol-only and 173 were multisubstance cases. The three most common comorbidities in multisubstance patients showed significant gender differences: psychiatric disorders (43% males vs 61% females; p = 0.022), chronic ethanol abuse (55% males vs 32% females; p = 0.002) and drug addiction (44% males vs 17% females; p = 0.001). Gender differences were also found for the most frequently co-ingested substances: benzodiazepines (35% males vs 43% females; p = 0.014), cannabis (45% males vs 24% females; p = 0.006) and cocaine (24% males vs 6% females; p = 0.001). Male and female ethanol-only patients were transferred to the intensive care unit in 8% of cases. In multisubstance cases, 32% of male and 43% of female patients were transferred to the intensive care unit (no significant gender difference). The psychiatric ward referral rate in male (30%) and female (48%) patients with multisubstance abuse was significantly different (p = 0.028). No significant gender difference in psychiatric ward referral rates was observed for ethanol-only patients (12% males, 17% females)., Conclusion: Among emergency department patients admitted with ethanol intoxication, gender differences in comorbidities, substance use and psychiatric ward referrals were highly significant among patients who presented with multisubstance abuse. Rates of intensive care unit transfer for patients with ethanol intoxication are substantial for both genders, reflecting relevant disease burden and resource demand, as well as the need for further preventive efforts.
- Published
- 2023
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72. Fluids and Electrolytes under Confinement in Single-Digit Nanopores.
- Author
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Aluru NR, Aydin F, Bazant MZ, Blankschtein D, Brozena AH, de Souza JP, Elimelech M, Faucher S, Fourkas JT, Koman VB, Kuehne M, Kulik HJ, Li HK, Li Y, Li Z, Majumdar A, Martis J, Misra RP, Noy A, Pham TA, Qu H, Rayabharam A, Reed MA, Ritt CL, Schwegler E, Siwy Z, Strano MS, Wang Y, Yao YC, Zhan C, and Zhang Z
- Abstract
Confined fluids and electrolyte solutions in nanopores exhibit rich and surprising physics and chemistry that impact the mass transport and energy efficiency in many important natural systems and industrial applications. Existing theories often fail to predict the exotic effects observed in the narrowest of such pores, called single-digit nanopores (SDNs), which have diameters or conduit widths of less than 10 nm, and have only recently become accessible for experimental measurements. What SDNs reveal has been surprising, including a rapidly increasing number of examples such as extraordinarily fast water transport, distorted fluid-phase boundaries, strong ion-correlation and quantum effects, and dielectric anomalies that are not observed in larger pores. Exploiting these effects presents myriad opportunities in both basic and applied research that stand to impact a host of new technologies at the water-energy nexus, from new membranes for precise separations and water purification to new gas permeable materials for water electrolyzers and energy-storage devices. SDNs also present unique opportunities to achieve ultrasensitive and selective chemical sensing at the single-ion and single-molecule limit. In this review article, we summarize the progress on nanofluidics of SDNs, with a focus on the confinement effects that arise in these extremely narrow nanopores. The recent development of precision model systems, transformative experimental tools, and multiscale theories that have played enabling roles in advancing this frontier are reviewed. We also identify new knowledge gaps in our understanding of nanofluidic transport and provide an outlook for the future challenges and opportunities at this rapidly advancing frontier.
- Published
- 2023
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73. Metabolic profile of transition period in ewes and its influence on passive immunity transference in lambs.
- Author
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Chagas DW, de Oliveira Feijó J, Corrêa MN, Furtado M, Gueretz JS, Peripolli V, Bianchi I, Moreira F, and Schwegler E
- Subjects
- Pregnancy, Sheep, Animals, Female, Calcium, Sheep, Domestic, Metabolome, Calcium, Dietary, Magnesium, Fatty Acids, Nonesterified
- Abstract
The intensification of ewe production, focusing on increasing prolificity, results in a higher incidence of metabolic disorders, especially in the transition period, which can lead to production losses with consequences for the health of the animals. The objective of this study was to evaluate the metabolic profile in transition period Lacaune ewes according to the parity and litter size born and its influence on the transference of passive immunity. Nineteen Lacaune ewes, with initial mean body weight of 76.36 ± 10.37 kg (SD), kept in a semi-extensive system and receiving the same diet, were used. Ewes were classified according to parity (primiparous and multiparous) and the litter size born at parturition (1, 2, and 3). On days - 14, - 7, and - 4 of the expected date of parturition and on days 1, 4, 7, and 14 days postpartum, blood sampling, the evaluation of the body condition score (BCS), and the weighing of animals were performed. Blood samples were taken from the lambs 48 h after birth. Colostrum was collected up to 6 h postpartum to determine the brix percentage. Serum concentrations of total plasma proteins (TPP), albumin, aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), beta-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), paraoxonase (PON1), calcium (Ca), and magnesium (Mg) were evaluated. In lambs, the blood parameters evaluated were TPP, albumin, GGT, and PON1. Lamb plasma was used to estimate colostrum efficiency, brix percentage immunity, and total plasma protein (PPT). Productive data, pre- and postpartum metabolic variables for ewes, lambs, and those related to colostrum brix were analyzed. The BCS had a reduction (p < 0.0001) in the postpartum period, which is evidenced on days 7 and 14 (2.88 and 2.73, respectively). Serum concentration of BHB presented the highest concentrations in the prepartum period for ewes that gave birth to triplets, from day - 14, and for ewes that gave birth to twins on day - 4 (p = 0.0245). Serum concentration of NEFA demonstrated the highest value on day 14 in primiparous (1.07; p = 0.0402). Calcium had the lowest concentrations on day 1 (8.85 mg/dl, p < 0.0001) and magnesium on day 3 (1.79 mg/dl, p < 0.0001) postpartum. The multiparous with two lambs had higher brix percentages (30.5%), and the lowest value was observed in primiparous ewes that gave birth to a single lamb (27.06%; p = 0.0395). Triplet lambs had the lowest weight (3.73 kg, p = 0.0007), and the best brix percentage in plasma was observed in twins (10.29%, p = 0.0174). Regardless of the parity, the ewes that presented the greatest metabolic challenge were those that gave birth to triplets, and these lambs presented the worst immunity and the lowest live weight. The quality of colostrum was influenced by the parity, and multiparous ewes that gave birth to triplets had the lowest brix percentage in the colostrum., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)
- Published
- 2023
- Full Text
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74. Multiframe Imaging of Micron and Nanoscale Bubble Dynamics.
- Author
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Egan GC, Lau EY, and Schwegler E
- Subjects
- Diagnostic Imaging, Lasers, Gold, Metal Nanoparticles
- Abstract
Here, we report on the direct sequential imaging of laser-induced cavitation of micron and nanoscale bubbles using Movie-Mode Dynamic Transmission Electron Microscopy (MM-DTEM). A 532 nm laser pulse (∼12 ns) was used to excite gold nanoparticles inside a ∼1.2 μm layer of water, and the resulting bubbles were observed with a series of nine electron pulses (∼10 ns) separated by as little as 40 ns peak to peak. Isolated nanobubbles were observed to collapse in less than 50 ns, while larger (∼2-3 μm) bubbles were observed to grow and collapse in less than 200 ns. Temporal profiles were generally asymmetric, possibly indicating faster growth than collapse dynamics, and the collapse time scale was found to be consistent with modeling and literature data from other techniques. More complex behavior was also observed for bubbles within proximity to each other, with interaction leading to longer lifetimes and more likely rebounding after collapse.
- Published
- 2022
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75. Distribution of cysts holding Ascocotyle (Phagicola) longa metacercariae in tissues and organs of mugilid.
- Author
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Gueretz JS, Boeing M, Murasaki J, Schwegler E, Moura AB, and Martins ML
- Subjects
- Animals, Metacercariae, Cysts veterinary, Fish Diseases, Heterophyidae, Smegmamorpha, Trematoda, Trematode Infections veterinary
- Abstract
Ascocotyle (Phagicola) longa is an etiological agent of human phagicolosis. Mugilids are the second intermediate host, the first being Heleobia australis, and mugilids predatory birds and mammals are its definitive hosts. The occurrence of cysts holding A. longa metacercariae is described in mugilids with a prevalence of up to 100%. The wide geographical distribution of A. longa and its intermediate hosts coupled with the rise in the consumption of raw or poorly cooked fish may elevate the risk of human infection. Therefore, in this study, we aimed to verify the distribution pattern of cysts holding A. longa in mugilids. The tissue and organ samples of these fish were processed in a domestic blender and examined under a stereoscopic microscope to identify the cysts holding the digenetic metacercariae. Of the 24 (100%) fish samples that were analyzed, 12 of Mugil curema and 12 of Mugil liza possessed cysts holding A. longa metacercariae. Digenetic cysts were identified to be present in the gills, heart, stomach, liver, intestines, mesentery, and muscular tissues collected from M. curema and M. liza. Conclusively, in M. curema, the cysts holding A. longa metacercariae were found to be distributed randomly throughout the fish body in almost every tissue and organ that was examined.
- Published
- 2021
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- View/download PDF
76. Ion Solvation and Transport in Narrow Carbon Nanotubes: Effects of Polarizability, Cation-π Interaction, and Confinement.
- Author
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Aydin F, Moradzadeh A, Bilodeau CL, Lau EY, Schwegler E, Aluru NR, and Pham TA
- Abstract
Understanding ion solvation and transport under confinement is critical for a wide range of emerging technologies, including water desalination and energy storage. While molecular dynamics (MD) simulations have been widely used to study the behavior of confined ions, considerable deviations between simulation results depending on the specific treatment of intermolecular interactions remain. In the following, we present a systematic investigation of the structure and dynamics of two representative solutions, that is, KCl and LiCl, confined in narrow carbon nanotubes (CNTs) with a diameter of 1.1 and 1.5 nm, using a combination of first-principles and classical MD simulations. Our simulations show that the inclusion of both polarization and cation-π interactions is essential for the description of ion solvation under confinement, particularly for large ions with weak hydration energies. Beyond the variation in ion solvation, we find that cation-π interactions can significantly influence the transport properties of ions in CNTs, particularly for KCl, where our simulations point to a strong correlation between ion dehydration and diffusion. Our study highlights the complex interplay between nanoconfinement and specific intermolecular interactions that strongly control the solvation and transport properties of ions.
- Published
- 2021
- Full Text
- View/download PDF
77. Similarities and differences between potassium and ammonium ions in liquid water: a first-principles study.
- Author
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Aydin F, Zhan C, Ritt C, Epsztein R, Elimelech M, Schwegler E, and Pham TA
- Abstract
Understanding ion solvation in liquid water is critical in optimizing materials for a wide variety of emerging technologies, including water desalination and purification. In this work, we report a systematic investigation and comparison of solvated K
+ and NH4 + using first-principles molecular dynamics simulations. Our simulations reveal a strong analogy in the solvation properties of the two ions, including the size of the solvation shell as well as the solvation strength. On the other hand, we find that the local water structure in the ion solvation is significantly different; specifically, NH4 + yields a smaller number of water molecules and a more ordered water structure in the first solvation shell due to the formation of hydrogen bonds between the ion and water molecules. Finally, our simulations indicate that a comparable solvation strength of the two ions is a result of an interplay between the nature of ion-water interaction and number of water molecules that can be accommodated in the ion solvation shell.- Published
- 2020
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78. Electronic structure of aqueous solutions: Bridging the gap between theory and experiments.
- Author
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Pham TA, Govoni M, Seidel R, Bradforth SE, Schwegler E, and Galli G
- Abstract
Predicting the electronic properties of aqueous liquids has been a long-standing challenge for quantum mechanical methods. However, it is a crucial step in understanding and predicting the key role played by aqueous solutions and electrolytes in a wide variety of emerging energy and environmental technologies, including battery and photoelectrochemical cell design. We propose an efficient and accurate approach to predict the electronic properties of aqueous solutions, on the basis of the combination of first-principles methods and experimental validation using state-of-the-art spectroscopic measurements. We present results of the photoelectron spectra of a broad range of solvated ions, showing that first-principles molecular dynamics simulations and electronic structure calculations using dielectric hybrid functionals provide a quantitative description of the electronic properties of the solvent and solutes, including excitation energies. The proposed computational framework is general and applicable to other liquids, thereby offering great promise in understanding and engineering solutions and liquid electrolytes for a variety of important energy technologies.
- Published
- 2017
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79. Comment on "New Ground-State Crystal Structure of Elemental Boron".
- Author
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Ogitsu T, Lordi V, Schwegler E, and Widom M
- Subjects
- Molecular Structure, Boron chemistry, Crystallography, X-Ray
- Published
- 2017
- Full Text
- View/download PDF
80. Structure and dynamics of aqueous solutions from PBE-based first-principles molecular dynamics simulations.
- Author
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Pham TA, Ogitsu T, Lau EY, and Schwegler E
- Abstract
Establishing an accurate and predictive computational framework for the description of complex aqueous solutions is an ongoing challenge for density functional theory based first-principles molecular dynamics (FPMD) simulations. In this context, important advances have been made in recent years, including the development of sophisticated exchange-correlation functionals. On the other hand, simulations based on simple generalized gradient approximation (GGA) functionals remain an active field, particularly in the study of complex aqueous solutions due to a good balance between the accuracy, computational expense, and the applicability to a wide range of systems. Such simulations are often performed at elevated temperatures to artificially "correct" for GGA inaccuracies in the description of liquid water; however, a detailed understanding of how the choice of temperature affects the structure and dynamics of other components, such as solvated ions, is largely unknown. To address this question, we carried out a series of FPMD simulations at temperatures ranging from 300 to 460 K for liquid water and three representative aqueous solutions containing solvated Na
+ , K+ , and Cl- ions. We show that simulations at 390-400 K with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional yield water structure and dynamics in good agreement with experiments at ambient conditions. Simultaneously, this computational setup provides ion solvation structures and ion effects on water dynamics consistent with experiments. Our results suggest that an elevated temperature around 390-400 K with the PBE functional can be used for the description of structural and dynamical properties of liquid water and complex solutions with solvated ions at ambient conditions.- Published
- 2016
- Full Text
- View/download PDF
81. Behavior of P85 and P188 Poloxamer Molecules: Computer Simulations Using United-Atom Force-Field.
- Author
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Goliaei A, Lau EY, Adhikari U, Schwegler E, and Berkowitz ML
- Subjects
- Air, Hydrophobic and Hydrophilic Interactions, Molecular Structure, Phosphatidylcholines chemistry, Solvents chemistry, Water chemistry, Computer Simulation, Lipid Bilayers chemistry, Models, Molecular, Poloxamer chemistry
- Abstract
To study the interaction between poloxamer molecules and lipid bilayers using molecular dynamics simulation technique with the united-atom resolution, we augmented the GROMOS force-field to include poloxamers. We validated the force-field by calculating the radii of gyration of two poloxamers, P85 and P188, solvated in water and by considering the poloxamer density distributions at the air/water interface. The emphasis of our simulations was on the study of the interaction between poloxamers and lipid bilayer. At the water/lipid bilayer interface, we observed that both poloxamers studied, P85 and P188, behaved like surfactants: the hydrophilic blocks of poloxamers became adsorbed at the polar interface, while their hydrophobic block penetrated the interface into the aliphatic tail region of the lipid bilayer. We also observed that when P85 and P188 poloxamers interacted with damaged membranes that contained pores, the hydrophobic blocks of copolymers penetrated into the membrane in the vicinity of the pore and compressed the membrane. Due to this compression, water molecules were evacuated from the pore.
- Published
- 2016
- Full Text
- View/download PDF
82. Reduction of liver function delays resumption of postpartum ovarian activity and alters the synthesis of acute phase proteins in dairy cows.
- Author
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Montagner P, Krause AR, Schwegler E, Weschenfelder MM, Rabassa VR, Schneider A, Pereira RA, Brauner CC, Del Pino FA, Gonçalves FM, and Corrêa MN
- Subjects
- Animals, Cattle physiology, Fatty Acids, Nonesterified, Female, Reproduction, Acute-Phase Proteins metabolism, Cattle blood, Lactation physiology, Liver physiology, Ovulation physiology, Postpartum Period physiology
- Abstract
The aim of this study was to evaluate the concentration of acute phase proteins, milk production, and resumption of postpartum ovarian activity of clinically healthy dairy cows in a semi-extensive system with different Liver Functionality Index (LFI) values. The animals were divided into two groups: Low LFI (LLFI: -7 to -12; n: 10) and High LFI (HLFI: -7 to -4; n: 10). Animals with LLFI had lower paraoxonase activity and lower albumin concentration in the pre- and postpartum periods (P<0.05), higher non-esterified fatty acids prepartum (P<0.005), and higher haptoglobin concentration postpartum (P<0.01). The LLFI group showed lower resumption of ovarian activity until 44days postpartum (29%; P<0.05) than HLFI (86%). Milk production did not differ between groups. Therefore, this study suggests that the LFI is an important biomarker of synthesis of acute phase proteins and the first ovulation interval, and it can be used to improve the production and reproductive performance., (Copyright © 2016 Elsevier Ltd. All rights reserved.)
- Published
- 2016
- Full Text
- View/download PDF
83. Exploring the free energy surface using ab initio molecular dynamics.
- Author
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Samanta A, Morales MA, and Schwegler E
- Abstract
Efficient exploration of configuration space and identification of metastable structures in condensed phase systems are challenging from both computational and algorithmic perspectives. In this regard, schemes that utilize a set of pre-defined order parameters to sample the relevant parts of the configuration space [L. Maragliano and E. Vanden-Eijnden, Chem. Phys. Lett. 426, 168 (2006); J. B. Abrams and M. E. Tuckerman, J. Phys. Chem. B 112, 15742 (2008)] have proved useful. Here, we demonstrate how these order-parameter aided temperature accelerated sampling schemes can be used within the Born-Oppenheimer and the Car-Parrinello frameworks of ab initio molecular dynamics to efficiently and systematically explore free energy surfaces, and search for metastable states and reaction pathways. We have used these methods to identify the metastable structures and reaction pathways in SiO2 and Ti. In addition, we have used the string method [W. E, W. Ren, and E. Vanden-Eijnden, Phys. Rev. B 66, 052301 (2002); L. Maragliano et al., J. Chem. Phys. 125, 024106 (2006)] within the density functional theory to study the melting pathways in the high pressure cotunnite phase of SiO2 and the hexagonal closed packed to face centered cubic phase transition in Ti.
- Published
- 2016
- Full Text
- View/download PDF
84. Shock Wave-Induced Damage of a Protein by Void Collapse.
- Author
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Lau EY, Berkowitz ML, and Schwegler E
- Subjects
- Kv1.2 Potassium Channel chemistry, Protein Structure, Tertiary, Cell Membrane metabolism, Kv1.2 Potassium Channel metabolism, Molecular Dynamics Simulation, Sound adverse effects
- Abstract
In this study, we report on a series of molecular dynamics simulations that were used to examine the effects of shock waves on a membrane-bound ion channel. A planar shock wave was found to compress the ion channel upon impact, but the protein geometry resembles the crystal structure as soon as the solvent density begins to dissipate. When a void was placed in close proximity to the membrane, the shock wave proved to be more destructive to the protein due to formation of a nanojet that results from the asymmetric collapse of the void. The nanojet was able to cause significant structural changes to the protein even at low piston velocities that are not able to directly cause poration of the membrane., (Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2016
- Full Text
- View/download PDF
85. Characterization of single nucleotide polymorphisms in the promoter region of the bovine paraoxonase 1 (PON1) gene affecting serum enzyme activity in dairy cows.
- Author
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Silveira PA, Schwegler E, Montagner P, Krause AR, Acosta DA, Halfen J, Garlet T, Barros CC, Corrêa MN, and Schneider A
- Subjects
- Animals, Aryldialkylphosphatase blood, Dairying, Female, Postpartum Period, Aryldialkylphosphatase genetics, Cattle metabolism, Polymorphism, Single Nucleotide, Promoter Regions, Genetic
- Abstract
The aim of the present study was to characterize single nucleotide polymorphisms (SNPs) in the promoter region of the bovine paraoxonase 1 (PON1) gene and determine their relationship with PON1 serum activity. Blood samples were collected from 47 Holstein cows during the periparturient period. Serum PON1 was measured and DNA extracted for PCR and sequencing of the promoter region of the PON1 gene. Seven novel SNPs were identified and of these, five SNPs, at positions -105, -221, -392, -611 and -674, upstream of the start of the published mRNA sequence (NM_001046269.2), were found to be associated with variability in serum PON1 activity (P < 0.05). The SNPs at positions -221 and -611 were located in regions predicted to bind to transcription factors linked to the acute phase response., (Copyright © 2015 Elsevier Ltd. All rights reserved.)
- Published
- 2015
- Full Text
- View/download PDF
86. Interfacial effects on the band edges of functionalized si surfaces in liquid water.
- Author
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Pham TA, Lee D, Schwegler E, and Galli G
- Abstract
By combining ab initio molecular dynamics simulations and many-body perturbation theory calculations of electronic energy levels, we determined the band edge positions of functionalized Si(111) surfaces in the presence of liquid water, with respect to vacuum and to water redox potentials. We considered surface terminations commonly used for Si photoelectrodes in water splitting experiments. We found that, when exposed to water, the semiconductor band edges were shifted by approximately 0.5 eV in the case of hydrophobic surfaces, irrespective of the termination. The effect of the liquid on band edge positions of hydrophilic surfaces was much more significant and determined by a complex combination of structural and electronic effects. These include structural rearrangements of the semiconductor surfaces in the presence of water, changes in the orientation of interfacial water molecules with respect to the bulk liquid, and charge transfer at the interfaces, between the solid and the liquid. Our results showed that the use of many-body perturbation theory is key to obtain results in agreement with experiments; they also showed that the use of simple computational schemes that neglect the detailed microscopic structure of the solid-liquid interface may lead to substantial errors in predicting the alignment between the solid band edges and water redox potentials.
- Published
- 2014
- Full Text
- View/download PDF
87. Associations between resumption of postpartum ovarian activity, uterine health and concentrations of metabolites and acute phase proteins during the transition period in Holstein cows.
- Author
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Krause AR, Pfeifer LF, Montagner P, Weschenfelder MM, Schwegler E, Lima ME, Xavier EG, Brauner CC, Schmitt E, Del Pino FA, Martins CF, Corrêa MN, and Schneider A
- Subjects
- Animals, Blood Glucose metabolism, Dairying, Female, Haptoglobins metabolism, Health, Insulin blood, Leukocyte Count, Leukocytes cytology, Ovulation physiology, Uterus cytology, Uterus metabolism, Acute-Phase Proteins metabolism, Cattle physiology, Energy Metabolism, Ovary physiology, Postpartum Period, Uterus immunology
- Abstract
The resumption of ovarian activity, uterine health, severity of the negative energy balance and the synthesis of inflammatory mediators during the transition period in dairy cows are interrelated. Therefore, the aim of this study was to evaluate the association between the resumption of postpartum ovarian activity and the percentage of polymorphonuclear (PMN) cells in endometrial cytology, lipid mobilization and the secretion of acute phase proteins. For this study, 20 multiparous Holstein cows were used. Blood samples that were collected from 21d before calving to 44d in milk (DIM) were analyzed for serum glucose, non-esterified fatty acids (NEFA), insulin, haptoglobin, albumin, paraoxonase and progesterone. Endometrial cytology was performed at 37±2DIM to evaluate the percentage of PMN cells in the uterine flushing. Cows were divided into two groups: (1) ovulatory cows (n=12), which returned to ovarian activity by 44±2DIM; and (2) anovulatory cows (n=8), which did not resume ovarian activity during this period. Ovulatory cows had a lower (P=0.05) percentage of PMN cells in endometrial cytology than anovulatory cows (26.3±8.3% vs. 53.4±16.9%, respectively). Ovulatory cows had higher serum albumin during the pre- (P=0.03) and postpartum periods (P=0.01), and tended to have lower haptoglobin concentrations in the prepartum period (P=0.07) and higher paraoxonase activity in the postpartum period (P=0.09). In conclusion, cows that resumed ovarian activity early in the postpartum period had higher albumin concentrations in the peripartum period, which were associated with a lower percentage of uterine PMN cells., (Copyright © 2014 Elsevier B.V. All rights reserved.)
- Published
- 2014
- Full Text
- View/download PDF
88. Hydrogen-bond dynamics of water at the interface with InP/GaP(001) and the implications for photoelectrochemistry.
- Author
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Wood BC, Schwegler E, Choi WI, and Ogitsu T
- Abstract
We investigate the structure, topology, and dynamics of liquid water at the interface with natively hydroxylated (001) surfaces of InP and GaP photoelectrodes. Using ab initio molecular dynamics simulations, we show that contact with the semiconductor surface enhances the water hydrogen-bond strength at the interface. This leads to the formation of an ice-like structure, within which dynamically driven water dissociation and local proton hopping are amplified. Nevertheless, the structurally similar and isovalent InP and GaP surfaces generate qualitatively different interfacial water dynamics. This can be traced to slightly more covalent-like character in the binding of surface adsorbates to GaP, which results in a more rigid hydrogen-bond network that limits the explored topological phase space. As a consequence, local proton hopping can give rise to long-range surface proton transport on InP, whereas the process is kinetically limited on GaP. This allows for spatial separation of individual stages of hydrogen-evolving, multistep reactions on InP(001). Possible implications for the mechanisms of cathodic water splitting and photocorrosion on the two surfaces are considered in light of available experimental evidence.
- Published
- 2013
- Full Text
- View/download PDF
89. Predictive value of prepartum serum metabolites for incidence of clinical and subclinical mastitis in grazing primiparous Holstein cows.
- Author
-
Schwegler E, Schneider A, Montagner P, Acosta DA, Pfeifer LF, Schmitt E, Rabassa VR, Del Pino FA, de Lima Gonzalez H, Timm CD, and Corrêa MN
- Subjects
- Animals, Asymptomatic Infections epidemiology, Biomarkers metabolism, Brazil epidemiology, Cell Count veterinary, Colorimetry veterinary, Energy Metabolism, Female, Incidence, Mastitis, Bovine epidemiology, Mastitis, Bovine etiology, Mastitis, Bovine metabolism, Parity, Peripartum Period, Postpartum Period, Pregnancy, Tropical Climate, Aspartate Aminotransferases blood, Blood Glucose metabolism, Cattle metabolism, Fatty Acids, Nonesterified blood, Mastitis, Bovine diagnosis
- Abstract
The aim of this study was to measure changes in biochemical markers in the peripartum period of primiparous Holstein cows diagnosed with subclinical and clinical mastitis. In this study, 37 dairy cows were monitored daily during milking until 60 days postpartum and were categorized according to the occurrence of clinical mastitis (group mastitis (GM), n = 9) or subclinical mastitis (group subclinical mastitis (GSUB), n = 10) or absence of symptoms (control group (CG), n = 18). Blood samples were collected weekly from -30 to 60 days from calving. Samples were grouped for prepartum (-30 to 0 days from calving), early postpartum (0 to 30 days from calving), and late postpartum (30 to 60 days from calving) periods. Prepartum serum non-esterified fatty acid (NEFA) concentration was higher in GM than in CG (P < 0.01). In addition, CG had higher prepartum serum glucose concentration than GM (P = 0.03). In the early postpartum period, aspartate aminotransferase (AST) activity was lower in CG than in GSUB (P < 0.05), and in the late postpartum period, AST activity was lower in CG than GSUB and GM (P = 0.01). Somatic cell count was higher during the early and late postpartum periods for GM and GSUB when compared to CG (P < 0.01). In this study, primiparous cows with low glucose and higher NEFA in the prepartum were more susceptible for mastitis in the early postpartum, probably due to low immune function associated to a more negative energy balance. In sum, increased prepartum serum NEFA concentration and decreased glucose in primiparous cows were associated with clinical mastitis incidence in the postpartum period.
- Published
- 2013
- Full Text
- View/download PDF
90. β-Rhombohedral boron: at the crossroads of the chemistry of boron and the physics of frustration.
- Author
-
Ogitsu T, Schwegler E, and Galli G
- Published
- 2013
- Full Text
- View/download PDF
91. Probing the Structure of Salt Water under Confinement with First-Principles Molecular Dynamics and Theoretical X-ray Absorption Spectroscopy.
- Author
-
Kulik HJ, Schwegler E, and Galli G
- Abstract
We investigated the structure of liquid water around cations (Na(+)) and anions (Cl(-)) confined inside of a (19,0) carbon nanotube with first-principles molecular dynamics and theoretical X-ray absorption spectroscopy (XAS). We found that the ions preferentially reside near the interface between the nanotube and the liquid. Upon confinement, the XAS signal of water molecules surrounding Na(+) exhibits enhanced pre-edge and reduced post-edge features with respect to that of pure water, at variance with the solvation shell of Na(+) in bulk water. Conversely, the first solvation shell of confined Cl(-) has a main-edge intensity comparable to that of bulk solvated Cl(-), likely as a result of a high number of acceptor hydrogen bonds in the first solvation shell. Confined nonsolvating water molecules exhibit bulk-like or water-monomer-like properties, depending on whether they belong to core or interfacial layers, respectively.
- Published
- 2012
- Full Text
- View/download PDF
92. Ligand-mediated modification of the electronic structure of CdSe quantum dots.
- Author
-
Lee JR, Whitley HD, Meulenberg RW, Wolcott A, Zhang JZ, Prendergast D, Lovingood DD, Strouse GF, Ogitsu T, Schwegler E, Terminello LJ, and van Buuren T
- Subjects
- Computer Simulation, Equipment Design, Equipment Failure Analysis, Ligands, Cadmium Compounds chemistry, Models, Chemical, Nanostructures chemistry, Nanostructures ultrastructure, Quantum Dots, Selenium Compounds chemistry
- Abstract
X-ray absorption spectroscopy and ab initio modeling of the experimental spectra have been used to investigate the effects of surface passivation on the unoccupied electronic states of CdSe quantum dots (QDs). Significant differences are observed in the unoccupied electronic structure of the CdSe QDs, which are shown to arise from variations in specific ligand-surface bonding interactions.
- Published
- 2012
- Full Text
- View/download PDF
93. Persistent medium-range order and anomalous liquid properties of Al(1-x)Cu(x) alloys.
- Author
-
Kang J, Zhu J, Wei SH, Schwegler E, and Kim YH
- Abstract
The development of short-to-medium-range order in atomic arrangements has generally been observed in noncrystalline solid systems such as metallic glasses. Whether such medium-range order (MRO) can exist in materials at well above their melting or glass-transition temperature has been a long-standing important scientific issue. Here, using ab initio molecular dynamics simulations, we show that a novel, persistent MRO exists in liquid Al-Cu alloys near the composition of CuAl3. The correlated atomic motions associated with the MRO give rise to a substantially enhanced viscosity in the vicinity of the composition. The component of the MRO liquid state gradually decreases with increasing temperature, and it disappears above a crossover temperature T(LLC). The continuous liquid-liquid crossover through a percolationlike transition leads to a pronounced heat capacity peak at T(LLC).
- Published
- 2012
- Full Text
- View/download PDF
94. Local structural models of complex oxygen- and hydroxyl-rich GaP/InP(001) surfaces.
- Author
-
Wood BC, Ogitsu T, and Schwegler E
- Abstract
We perform density-functional theory calculations on model surfaces to investigate the interplay between the morphology, electronic structure, and chemistry of oxygen- and hydroxyl-rich surfaces of InP(001) and GaP(001). Four dominant local oxygen topologies are identified based on the coordination environment: M-O-M and M-O-P bridges for the oxygen-decorated surface; and M-[OH]-M bridges and atop M-OH structures for the hydroxyl-decorated surface (M = In, Ga). Unique signatures in the electronic structure are linked to each of the bond topologies, defining a map to structural models that can be used to aid the interpretation of experimental probes of native oxide morphology. The M-O-M bridge can create a trap for hole carriers upon imposition of strain or chemical modification of the bonding environment of the M atoms, which may contribute to the observed photocorrosion of GaP/InP-based electrodes in photoelectrochemical cells. Our results suggest that a simplified model incorporating the dominant local bond topologies within an oxygen adlayer should reproduce the essential chemistry of complex oxygen-rich InP(001) or GaP(001) surfaces, representing a significant advantage from a modeling standpoint., (© 2012 American Institute of Physics)
- Published
- 2012
- Full Text
- View/download PDF
95. Local effects in the X-ray absorption spectrum of salt water.
- Author
-
Kulik HJ, Marzari N, Correa AA, Prendergast D, Schwegler E, and Galli G
- Subjects
- Calcium chemistry, Hydrogen Bonding, Magnesium chemistry, Sodium chemistry, X-Ray Absorption Spectroscopy, Salts chemistry, Water chemistry
- Abstract
Both first-principles molecular dynamics and theoretical X-ray absorption spectroscopy have been used to investigate the aqueous solvation of cations in 0.5 M MgCl(2), CaCl(2), and NaCl solutions. We focus here on the species-specific effects that Mg(2+), Ca(2+), and Na(+) have on the X-ray absorption spectrum of the respective solutions. For the divalent cations, we find that the hydrogen-bonding characteristics of the more rigid magnesium first-shell water molecules differ from those in the more flexible solvation shell surrounding calcium. In particular, the first solvation shell water molecules of calcium are able to form acceptor hydrogen bonds, and this results in an enhancement of a post-edge peak near 540 eV. The absence of acceptor hydrogen bonds for magnesium first shell water molecules provides an explanation for the experimental and theoretical observation of a lack of enhancement at the post-main-edge peak. For the sodium monovalent cation we find that the broad tilt angle distribution results in a broadening of postedge features, despite populations in donor-and-acceptor configurations consistent with calcium. We also present the reaveraged spectra of the MgCl(2), CaCl(2), and NaCl solutions and show that trends apparent with increasing concentration (0.5, 2.0, 4.0 M) are consistent with experiment. Finally, we examine more closely both the effect that cation coordination number has on the hydrogen-bonding network and the relative perturbation strength of the cations on lone pair oxygen orbitals.
- Published
- 2010
- Full Text
- View/download PDF
96. Evidence for a first-order liquid-liquid transition in high-pressure hydrogen from ab initio simulations.
- Author
-
Morales MA, Pierleoni C, Schwegler E, and Ceperley DM
- Abstract
Using quantum simulation techniques based on either density functional theory or quantum Monte Carlo, we find clear evidence of a first-order transition in liquid hydrogen, between a low conductivity molecular state and a high conductivity atomic state. Using the temperature dependence of the discontinuity in the electronic conductivity, we estimate the critical point of the transition at temperatures near 2,000 K and pressures near 120 GPa. Furthermore, we have determined the melting curve of molecular hydrogen up to pressures of 200 GPa, finding a reentrant melting line. The melting line crosses the metalization line at 700 K and 220 GPa using density functional energetics and at 550 K and 290 GPa using quantum Monte Carlo energetics.
- Published
- 2010
- Full Text
- View/download PDF
97. Ammonium salicylate: a synchrotron study.
- Author
-
Klepeis JH, Evans WJ, Zaitseva N, Schwegler E, and Teat SJ
- Abstract
The structure of the title salt, NH(4) (+)·C(7)H(5)O(3) (-), is stabilized by substantial hydrogen bonding between ammonium cations and salicylate anions that links the components into a two-dimensional array.
- Published
- 2009
- Full Text
- View/download PDF
98. Electronic effects in the IR spectrum of water under confinement.
- Author
-
Donadio D, Cicero G, Schwegler E, Sharma M, and Galli G
- Subjects
- Computer Simulation, Spectrophotometry, Infrared, Electrons, Water chemistry
- Abstract
We compare calculations of infrared (IR) spectra of water confined between nonpolar surfaces, obtained by molecular dynamics simulations with forces either computed using density functional theory or modeled by empirical potentials. Our study allows for the identification of important electronic effects, contributing to IR signals, that are not included in simulations based on empirical force fields, and cannot be extracted from the analysis of vibrational density of states. These effects originate from electronic charge fluctuations involving both surface and water molecules in close proximity of the interface. The implications of our findings for the interpretation of experimental data are discussed.
- Published
- 2009
- Full Text
- View/download PDF
99. Imperfect crystal and unusual semiconductor: boron, a frustrated element.
- Author
-
Ogitsu T, Gygi F, Reed J, Motome Y, Schwegler E, and Galli G
- Abstract
All elements, except for helium, appear to solidify into crystalline forms at zero temperature, and it is generally assumed that the introduction of lattice defects results in an increase in internal energy. beta-Rhombohedral boron, a thermodynamically stable form of elemental boron at high temperature, is known to have a large amount of partial occupied sites, seemingly in conflict with our common knowledge. By using lattice Monte Carlo techniques combined with ab initio calculations, we find that the beta-phase is stabilized by a macroscopic amount of intrinsic defects that are responsible not only for entropic effects but also for a reduction in internal energy. These defects enable the conversion of two-center to three-center bonds and are accompanied by the presence of localized, nonconductive electronic states in the optical gap. In addition we find that the ab initio Ising model describing the partial occupancy of beta-boron has macroscopic residual entropy, suggesting that boron is a frustrated system analogous to ice and spin ice.
- Published
- 2009
- Full Text
- View/download PDF
100. Melting of ice under pressure.
- Author
-
Schwegler E, Sharma M, Gygi F, and Galli G
- Abstract
The melting of ice under pressure is investigated with a series of first-principles molecular dynamics simulations. In particular, a two-phase approach is used to determine the melting temperature of the ice-VII phase in the range of 10-50 GPa. Our computed melting temperatures are consistent with existing diamond anvil cell experiments. We find that for pressures between 10 and 40 GPa, ice melts as a molecular solid. For pressures above approximately 45 Gpa, there is a sharp increase in the slope of the melting curve because of the presence of molecular dissociation and proton diffusion in the solid before melting. The onset of significant proton diffusion in ice-VII as a function of increasing temperature is found to be gradual and bears many similarities to that of a type-II superionic solid.
- Published
- 2008
- Full Text
- View/download PDF
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