1
|
Plasma Protein Biomarkers Distinguish Multisystem Inflammatory Syndrome in Children From Other Pediatric Infectious and Inflammatory Diseases. Pediatr Infect Dis J 2024; 43:444-453. [PMID: 38359342 PMCID: PMC11003410 DOI: 10.1097/inf.0000000000004267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/19/2023] [Indexed: 02/17/2024]
Abstract
BACKGROUND Multisystem inflammatory syndrome in children (MIS-C) is a rare but serious hyperinflammatory complication following infection with severe acute respiratory syndrome coronavirus 2. The mechanisms underpinning the pathophysiology of MIS-C are poorly understood. Moreover, clinically distinguishing MIS-C from other childhood infectious and inflammatory conditions, such as Kawasaki disease or severe bacterial and viral infections, is challenging due to overlapping clinical and laboratory features. We aimed to determine a set of plasma protein biomarkers that could discriminate MIS-C from those other diseases. METHODS Seven candidate protein biomarkers for MIS-C were selected based on literature and from whole blood RNA sequencing data from patients with MIS-C and other diseases. Plasma concentrations of ARG1, CCL20, CD163, CORIN, CXCL9, PCSK9 and ADAMTS2 were quantified in MIS-C (n = 22), Kawasaki disease (n = 23), definite bacterial (n = 28) and viral (n = 27) disease and healthy controls (n = 8). Logistic regression models were used to determine the discriminatory ability of individual proteins and protein combinations to identify MIS-C and association with severity of illness. RESULTS Plasma levels of CD163, CXCL9 and PCSK9 were significantly elevated in MIS-C with a combined area under the receiver operating characteristic curve of 85.7% (95% confidence interval: 76.6%-94.8%) for discriminating MIS-C from other childhood diseases. Lower ARG1 and CORIN plasma levels were significantly associated with severe MIS-C cases requiring inotropes, pediatric intensive care unit admission or with shock. CONCLUSION Our findings demonstrate the feasibility of a host protein biomarker signature for MIS-C and may provide new insight into its pathophysiology.
Collapse
|
2
|
Rapid nanopore sequencing and predictive susceptibility testing of positive blood cultures from intensive care patients with sepsis. Microbiol Spectr 2024; 12:e0306523. [PMID: 38193658 PMCID: PMC10846127 DOI: 10.1128/spectrum.03065-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 12/15/2023] [Indexed: 01/10/2024] Open
Abstract
We aimed to evaluate the performance of Oxford Nanopore Technologies (ONT) sequencing from positive blood culture (BC) broths for bacterial identification and antimicrobial susceptibility prediction. Patients with suspected sepsis in four intensive care units were prospectively enrolled. Human-depleted DNA was extracted from positive BC broths and sequenced using ONT (MinION). Species abundance was estimated using Kraken2, and a cloud-based system (AREScloud) provided in silico predictive antimicrobial susceptibility testing (AST) from assembled contigs. Results were compared to conventional identification and phenotypic AST. Species-level agreement between conventional methods and AST predicted from sequencing was 94.2% (49/52), increasing to 100% in monomicrobial infections. In 262 high-quality AREScloud AST predictions across 24 samples, categorical agreement (CA) was 89.3%, with major error (ME) and very major error (VME) rates of 10.5% and 12.1%, respectively. Over 90% CA was achieved for some taxa (e.g., Staphylococcus aureus) but was suboptimal for Pseudomonas aeruginosa. In 470 AST predictions across 42 samples, with both high quality and exploratory-only predictions, overall CA, ME, and VME rates were 87.7%, 8.3%, and 28.4%. VME rates were inflated by false susceptibility calls in a small number of species/antibiotic combinations with few representative resistant isolates. Time to reporting from sequencing could be achieved within 8-16 h from BC positivity. Direct sequencing from positive BC broths is feasible and can provide accurate predictive AST for some species. ONT-based approaches may be faster but significant improvements in accuracy are required before it can be considered for clinical use.IMPORTANCESepsis and bloodstream infections carry a high risk of morbidity and mortality. Rapid identification and susceptibility prediction of causative pathogens, using Nanopore sequencing direct from blood cultures, may offer clinical benefit. We assessed this approach in comparison to conventional phenotypic methods and determined the accuracy of species identification and susceptibility prediction from genomic data. While this workflow holds promise, and performed well for some common bacterial species, improvements in sequencing accuracy and more robust predictive algorithms across a diverse range of organisms are required before this can be considered for clinical use. However, results could be achieved in timeframes that are faster than conventional phenotypic methods.
Collapse
|
3
|
External validation of a multivariable prediction model for identification of pneumonia and other serious bacterial infections in febrile immunocompromised children. Arch Dis Child 2023; 109:58-66. [PMID: 37640431 DOI: 10.1136/archdischild-2023-325869] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 08/14/2023] [Indexed: 08/31/2023]
Abstract
OBJECTIVE To externally validate and update the Feverkids tool clinical prediction model for differentiating bacterial pneumonia and other serious bacterial infections (SBIs) from non-SBI causes of fever in immunocompromised children. DESIGN International, multicentre, prospective observational study embedded in PErsonalised Risk assessment in Febrile illness to Optimise Real-life Management across the European Union (PERFORM). SETTING Fifteen teaching hospitals in nine European countries. PARTICIPANTS Febrile immunocompromised children aged 0-18 years. METHODS The Feverkids clinical prediction model predicted the probability of bacterial pneumonia, other SBI or no SBI. Model discrimination, calibration and diagnostic performance at different risk thresholds were assessed. The model was then re-fitted and updated. RESULTS Of 558 episodes, 21 had bacterial pneumonia, 104 other SBI and 433 no SBI. Discrimination was 0.83 (95% CI 0.71 to 0.90) for bacterial pneumonia, with moderate calibration and 0.67 (0.61 to 0.72) for other SBIs, with poor calibration. After model re-fitting, discrimination improved to 0.88 (0.79 to 0.96) and 0.71 (0.65 to 0.76) and calibration improved. Predicted risk <1% ruled out bacterial pneumonia with sensitivity 0.95 (0.86 to 1.00) and negative likelihood ratio (LR) 0.09 (0.00 to 0.32). Predicted risk >10% ruled in bacterial pneumonia with specificity 0.91 (0.88 to 0.94) and positive LR 6.51 (3.71 to 10.3). Predicted risk <10% ruled out other SBIs with sensitivity 0.92 (0.87 to 0.97) and negative LR 0.32 (0.13 to 0.57). Predicted risk >30% ruled in other SBIs with specificity 0.89 (0.86 to 0.92) and positive LR 2.86 (1.91 to 4.25). CONCLUSION Discrimination and calibration were good for bacterial pneumonia but poorer for other SBIs. The rule-out thresholds have the potential to reduce unnecessary investigations and antibiotics in this high-risk group.
Collapse
|
4
|
Nitric Oxide on Extracorporeal Membrane Oxygenation in Neonates and Children (NECTAR Trial): Protocol for a Randomized Controlled Trial. JMIR Res Protoc 2023; 12:e43760. [PMID: 36920455 PMCID: PMC10131908 DOI: 10.2196/43760] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 01/11/2023] [Accepted: 01/28/2023] [Indexed: 01/30/2023] Open
Abstract
BACKGROUND Extracorporeal membrane oxygenation (ECMO) provides support for the pulmonary or cardiovascular function of children in whom the predicted mortality risk remains very high. The inevitable host inflammatory response and activation of the coagulation cascade due to the extracorporeal circuit contribute to additional morbidity and mortality in these patients. Mixing nitric oxide (NO) into the sweep gas of ECMO circuits may reduce the inflammatory and coagulation cascade activation during ECMO support. OBJECTIVE The purpose of this study is to test the feasibility and safety of mixing NO into the sweep gas of ECMO systems and assess its effect on inflammation and coagulation system activation through a pilot randomized controlled trial. METHODS The Nitric Oxide on Extracorporeal Membrane Oxygenation in Neonates and Children (NECTAR) trial is an open-label, parallel-group, pilot randomized controlled trial to be conducted at a single center. Fifty patients who require ECMO support will be randomly assigned to receive either NO mixed into the sweep gas of the ECMO system at 20 ppm for the duration of ECMO or standard care (no NO) in a 1:1 ratio, with stratification by support type (veno-venous vs veno-arterial ECMO). RESULTS Outcome measures will focus on feasibility (recruitment rate and consent rate, and successful inflammatory marker measurements), the safety of the intervention (oxygenation and carbon dioxide control within defined parameters and methemoglobin levels), and proxy markers of efficacy (assessment of cytokines, chemokines, and coagulation factors to assess the impact of NO on host inflammation and coagulation cascade activation, clotting of ECMO components, including computer tomography scanning of oxygenators for clot assessments), bleeding complications, as well as total blood product use. Survival without ECMO and the length of stay in the pediatric intensive care unit (PICU) are clinically relevant efficacy outcomes. Long-term outcomes include neurodevelopmental assessments (Ages and Stages Questionnaire, Strength and Difficulties Questionnaire, and others) and quality of life (Pediatric Quality of Life Inventory and others) measured at 6 and 12 months post ECMO cannulation. Analyses will be conducted on an intention-to-treat basis. CONCLUSIONS The NECTAR study investigates the safety and feasibility of NO as a drug intervention during extracorporeal life support and explores its efficacy. The study will investigate whether morbidity and mortality in patients treated with ECMO can be improved with NO. The intervention targets adverse outcomes in patients who are supported by ECMO and who have high expected mortality and morbidity. The study will be one of the largest randomized controlled trials performed among pediatric patients supported by ECMO. TRIAL REGISTRATION Australian New Zealand Clinical Trials Registry ACTRN12619001518156; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=376869. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID) DERR1-10.2196/43760.
Collapse
|
5
|
Role of extracorporeal membrane oxygenation in pediatric cancer patients: a systematic review and meta-analysis of observational studies. Ann Intensive Care 2022; 12:8. [PMID: 35092500 PMCID: PMC8800958 DOI: 10.1186/s13613-022-00983-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 01/13/2022] [Indexed: 01/10/2023] Open
Abstract
Background The use of extracorporeal membrane oxygenation (ECMO) in pediatric patients with underlying malignancies remains controversial. However, in an era in which the survival rates for children with malignancies have increased significantly and several recent reports have demonstrated effective ECMO use in children with cancer, we aimed to estimate the outcome and complications of ECMO treatment in these children. Methods We searched MEDLINE, Embase and CINAHL databases for studies on the use ECMO in pediatric patients with an underlying malignancy from inception to September 2020. This review was conducted in adherence to Preferred Reporting Items for Systematic Review and Meta-Analysis statement. Study eligibility was independently assessed by two authors and disagreements resolved by a third author. Included studies were evaluated for quality using the Newcastle–Ottawa Scale (NOS). Random effects meta-analyses (DerSimonian and Laird) were performed. The primary outcomes were mortality during ECMO or hospital mortality. Results Thirteen retrospective, observational cohort studies were included, most of moderate quality (625 patients). The commonest indication for ECMO was severe respiratory failure (92%). Pooled mortality during ECMO was 55% (95% confidence interval [CI], 47–63%) and pooled hospital mortality was 60% (95% CI 54–67%). Although heterogeneity among the included studies was low, confidence intervals were large. In addition, the majority of the data were derived from registries with overlapping patients which were excluded for the meta-analyses to prevent resampling of the same participants across the included studies. Finally, there was a lack of consistent complications reporting among the studies. Conclusion Significantly higher mortalities than in general PICU patients was reported with the use of ECMO in children with malignancies. Although these results need to be interpreted with caution due to the lack of granular data, they suggest that ECMO appears to represents a viable rescue option for selected patients with underlying malignancies. There is an urgent need for additional data to define patients for whom ECMO may provide benefit or harm. Supplementary Information The online version contains supplementary material available at 10.1186/s13613-022-00983-0.
Collapse
|
6
|
Long-term outcomes following paediatric sepsis – A narrative review. Aust Crit Care 2022. [DOI: 10.1016/j.aucc.2022.08.048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
|
7
|
Individualized precision dosing approaches to optimize antimicrobial therapy in pediatric populations. Expert Rev Clin Pharmacol 2021; 14:1383-1399. [PMID: 34313180 DOI: 10.1080/17512433.2021.1961578] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Introduction:Severe infections continue to impose a major burden on critically ill children and mortality rates remain stagnant. Outcomes rely on accurate and timely delivery of antimicrobials achieving target concentrations in infected tissue. Yet, developmental aspects, disease-related variables, and host factors may severely alter antimicrobial pharmacokinetics in pediatrics. The emergence of antimicrobial resistance increases the need for improved treatment approaches.Areas covered:This narrative review explores why optimization of antimicrobial therapy in neonates, infants, children, and adolescents is crucial and summarizes the possible dosing approaches to achieve antimicrobial individualization. Finally, we outline a roadmap toward scientific evidence informing the development and implementation of precision antimicrobial dosing in critically ill children.The literature search was conducted on PubMed using the following keywords: neonate, infant, child, adolescent, pediatrics, antimicrobial, pharmacokinetic, pharmacodynamic target, Bayes dosing software, optimizing, individualizing, personalizing, precision dosing, drug monitoring, validation, attainment, and software implementation. Further articles were sought from the references of the above searched articles.Expert opinion:Recently, technological innovations have emerged that enabled the development of individualized antimicrobial dosing approaches in adults. More work is required in pediatrics to make individualized antimicrobial dosing approaches widely operationalized in this population.
Collapse
|
8
|
Bacteremia in Childhood Life-Threatening Infections in Urban Gambia: EUCLIDS in West Africa. Open Forum Infect Dis 2019; 6:ofz332. [PMID: 31660408 PMCID: PMC6798247 DOI: 10.1093/ofid/ofz332] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 07/23/2019] [Indexed: 01/13/2023] Open
Abstract
Background The limited availability of microbiology services in sub-Saharan Africa impedes accurate diagnosis of bacterial pathogens and understanding of trends in prevalence and antibiotic sensitivities. We aimed to characterize bacteremia among hospitalized children in The Gambia and to identify factors associated with bacteremia and mortality. Methods We prospectively studied children presenting with suspected severe infection to 2 urban hospitals in The Gambia, between January 2013 and September 2015. Demographic and anthropometric data, clinical features, management, and blood culture results were documented. Urine screens for antibiotic activity were performed in a subset of participants. Results Of 411 children enrolled (median age, 29 months; interquartile range, 11–82), 79.5% (325 of 409) reported prehospital antibiotic use. Antimicrobial activity by urinary screen for antibiotic activity was detected in 70.8% (n = 80 of 113). Sixty-six bacterial pathogens were identified in 65 (15.8%) participants and Staphylococcus aureus predominated. Gram-positive organisms were more commonly identified than Gram-negative (P < .01). Antibiotic resistance against first-line antimicrobials (ampicillin and gentamicin) was common among Gram-negative bacteria (39%; range, 25%–100%). Factors significantly associated with bacteremia included the following: gender, hydration status, musculoskeletal examination findings, admission to the Medical Research Council The Gambia at London School of Hygiene & Tropical Medicine hospital, and meeting sepsis criteria. Those associated with increased mortality were presence of a comorbidity, clinical pallor, tachypnea, and altered consciousness. Tachycardia was associated with reduced mortality. Conclusions The bacteremia rate in children with suspected childhood life-threatening infectious diseases in The Gambia is high. The pattern of pathogen prevalence and antimicrobial resistance has changed over time compared with previous studies illustrating the importance of robust bacterial surveillance programs in resource-limited settings.
Collapse
|
9
|
Fluid bolus therapy in critically ill children: a survey of practice among paediatric intensive care doctors in Australia and New Zealand. CRIT CARE RESUSC 2018; 20:131-138. [PMID: 29852852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
OBJECTIVE Fluid bolus therapy (FBT) is a widely used intervention in paediatric critical illness. The aim of this study was to describe the attitudes and practices towards FBT of paediatric intensive care doctors in Australia and New Zealand. DESIGN An internet-based survey of paediatric intensive care doctors in Australia and New Zealand between 7 and 30 November 2016. SETTING Paediatric intensive care units with greater than 400 admissions annually. PARTICIPANTS Paediatric intensive care specialists and junior medical staff. MAIN OUTCOME MEASURES Preferences for FBT and markers of fluid responsiveness. RESULTS There were 106/175 respondents (61%); 0.9% saline and 4% albumin are used frequently or almost always by 86% and 57% of respondents respectively. The preferred volume and duration were 10 mL/kg in less than 10 minutes. The highest rated markers of fluid responsiveness were heart rate and blood pressure - rated as "good" or "very good" by 75% and 58% of respondents respectively. Central venous saturations and serum lactate were the highest rated biochemical markers. The most frequently expected magnitude of change for heart rate and blood pressure was 6-15% by 89% and 76% of respondents respectively. The preferred fluid composition for sepsis, trauma, traumatic brain injury and acute lung injury was 0.9% saline, and 4% albumin for post-operative cardiac surgery. CONCLUSIONS Paediatric intensive care doctors prefer 0.9% saline and 4% albumin for FBT. Heart rate and blood pressure are the most preferred markers to assess fluid responsiveness. Preferences for FBT in specific conditions exist.
Collapse
|
10
|
Time for Sepsis-3 in kids? – Prognostic accuracy of age-adapted SOFA, SIRS, PELOD-2, and qSOFA in children with infection. Aust Crit Care 2018. [DOI: 10.1016/j.aucc.2017.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
|
11
|
Time for Sepsis-3 in kids? – Prognostic accuracy of age-adapted SOFA, SIRS, PELOD-2, and qSOFA in children with infection. Aust Crit Care 2018. [DOI: 10.1016/j.aucc.2017.12.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
|
12
|
Nasal High-Flow Therapy in Children: A Survey of Current Practice in Australia. J Paediatr Child Health 2017; 53:1031-1032. [PMID: 28975751 DOI: 10.1111/jpc.13695] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 06/21/2017] [Indexed: 11/29/2022]
|
13
|
|
14
|
Burden of disease and change in practice in critically ill infants with bronchiolitis in Australia and New Zealand 2002 to 2014. Aust Crit Care 2017. [DOI: 10.1016/j.aucc.2017.02.067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
|
15
|
|
16
|
|
17
|
[A young child with acute abdomen and iron deficiency anemia]. PRAXIS 2006; 95:913-6. [PMID: 16774051 DOI: 10.1024/0369-8394.95.22.913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The case of a 20 month-old girl that was admitted to the emergency ward because of worsening of her general condition in the setting of acute non-bloody gastroenteritis is reported. The clinical examination revealed signs of severe dehydration and a prominent tender abdomen. Laboratory evaluation showed leucocytosis, elevated C-reactive protein and severe hypochromic microcytic anemia. Abdominal X-ray revealed diffuse meteorism. The child underwent laparascopic evaluation. A perforated Meckel's diverticulum was found. Perforation and anemia due to occult bleeding are unusual presentations of Meckel's diverticulum. The differential diagnosis of children presenting with an acute abdomen with special focus on Meckel's diverticulum is discussed.
Collapse
|
18
|
Study of adsorption and viscoelastic properties of proteins with a quartz crystal microbalance by measuring the oscillation amplitude. J Colloid Interface Sci 2006; 261:291-8. [PMID: 16256534 DOI: 10.1016/s0021-9797(03)00089-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2002] [Accepted: 01/16/2003] [Indexed: 11/20/2022]
Abstract
The adsorption kinetics of protein A, BSA, IgG, and fibronectin has been investigated using a homemade quartz crystal microbalance. Information about the energy losses appearing in the system is measured by the maximal oscillation amplitude and the dissipation factor. Only the maximal oscillation amplitude allows us to distinguish the different contributions of liquid and mass to the total frequency shift. The adsorption of proteins has been performed on Ti and Au surfaces at different concentrations. The amount of irreversible adsorbed protein A and IgG increases with increasing bulk concentrations. On Au more proteins adsorb, but their biological activity is reduced in comparison to Ti. Protein A forms a first monolayer in a few seconds, which shows practically no energy losses, and following this a second monolayer is formed. The adsorption rate for the second monolayer is much smaller and energy losses are present. Fibronectin is forming a very viscoelastic system, whose mechanical properties are affected by immersion in different buffer solutions.
Collapse
|
19
|
Simultaneous measurement of the maximum oscillation amplitude and the transient decay time constant of the QCM reveals stiffness changes of the adlayer. Anal Bioanal Chem 2003; 377:570-7. [PMID: 14504678 DOI: 10.1007/s00216-003-2081-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2003] [Revised: 05/01/2003] [Accepted: 05/20/2003] [Indexed: 11/24/2022]
Abstract
Interpretation of adsorption kinetics measured with a quartz crystal microbalance (QCM) can be difficult for adlayers undergoing modification of their mechanical properties. We have studied the behavior of the oscillation amplitude, A(0), and the decay time constant, tau, of quartz during adsorption of proteins and cells, by use of a home-made QCM. We are able to measure simultaneously the frequency, f, the dissipation factor, D, the maximum amplitude, A(0), and the transient decay time constant, tau, every 300 ms in liquid, gaseous, or vacuum environments. This analysis enables adsorption and modification of liquid/mass properties to be distinguished. Moreover the surface coverage and the stiffness of the adlayer can be estimated. These improvements promise to increase the appeal of QCM methodology for any applications measuring intimate contact of a dynamic material with a solid surface.
Collapse
|
20
|
Electronic structure of the YH3 phase from angle-resolved photoemission spectroscopy. PHYSICAL REVIEW LETTERS 2003; 90:196804. [PMID: 12785971 DOI: 10.1103/physrevlett.90.196804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2002] [Indexed: 05/24/2023]
Abstract
Yttrium can be loaded with hydrogen up to high concentrations causing dramatic structural and electronic changes of the host lattice. We report on angle-resolved photoemission experiments of the Y trihydride phase. Most importantly, we find the absence of metal d bands at the Fermi level and a set of flat, H-induced bands located at much higher binding energy than predicted, indicating an increased electron affinity at H sites.
Collapse
|
21
|
Abstract
BACKGROUND Treatment of HIV-1-infected individuals with antiretrovirals can result in sustained suppression of plasma viral RNA at concentrations below the detection limit of available assays. However, continuing virus replication has been detected in patients with viral RNA in plasma suppressed for months to years, and many cell types are known to act as reservoirs or carriers for the virus. In vitro, erythrocytes bind HIV-1 immune complexes, so we tested for a circulating pool of HIV-1 associated with erythrocytes in people with HIV-1 infection. METHODS We investigated 82 chronically HIV-1-infected individuals. Plasma, white cells, and erythrocytes were tested for HIV-1 RNA by RT-PCR. FINDINGS Erythrocyte-associated HIV-1 RNA was detected in 80 of 82 individuals. In 23, plasma HIV-1 RNA had been undetectable (<20 copies/mL) for up to 32 months; in corresponding erythrocyte samples, there were up to 82878 HIV-1 RNA copies per mL whole blood. HIV-1 associated with erythrocytes in vivo was shown to be infectious. Within the subgroup of patients with undetectable plasma viral load, higher numbers of HIV-1 associated with erythrocytes were correlated with a history of advanced clinical stages of HIV-1 infection (p=0.014). INTERPRETATION A pool of HIV-1 is associated with erythrocytes even after long-term suppression of viral RNA in plasma. This finding is direct evidence for continuing virus replication or release in these individuals. Quantification of this viral pool may help to judge suppression of HIV-1 replication in individuals with undetectable plasma HIV-1 RNA.
Collapse
|
22
|
Abstract
Mobility--the transport of people and goods - is a socioeconomic reality that will surely increase in the coming years. It should be safe, economic and reasonably clean. Little energy needs to be expended to overcome potential energy changes, but a great deal is lost through friction (for cars about 10 kWh per 100 km) and low-efficiency energy conversion. Vehicles can be run either by connecting them to a continuous supply of energy or by storing energy on board. Hydrogen would be ideal as a synthetic fuel because it is lightweight, highly abundant and its oxidation product (water) is environmentally benign, but storage remains a problem. Here we present recent developments in the search for innovative materials with high hydrogen-storage capacity.
Collapse
|
23
|
Formation of a stable decagonal quasicrystalline Al-Pd-Mn surface layer. PHYSICAL REVIEW LETTERS 2001; 87:195506. [PMID: 11690424 DOI: 10.1103/physrevlett.87.195506] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2001] [Indexed: 05/23/2023]
Abstract
We report the in situ formation of an ordered equilibrium decagonal Al-Pd-Mn quasicrystal overlayer on the fivefold symmetric surface of an icosahedral Al-Pd-Mn monograin. The decagonal structure of the epilayer is evidenced by x-ray photoelectron diffraction, low-energy electron diffraction, and electron backscatter diffraction. This overlayer is also characterized by a reduced density of states near the Fermi edge as expected for quasicrystals. This is the first time that a millimeter-size surface of the stable decagonal Al-Pd-Mn is obtained, studied, and compared to its icosahedral counterpart.
Collapse
|
24
|
Abstract
A new nucleation method to form diamond by chemically pretreating silicon (111) surfaces is reported. The nucleation consists of binding covalently 2,2-divinyladamantane molecules on the silicon substrate. Then low-pressure diamond growth was performed for 2 h via microwave plasma CVD in a tubular deposition system. The resulting diamond layers presented a good cristallinity and the Raman spectra showed a single very sharp peak at 1331 cm(-1), indicating high-quality diamonds.
Collapse
|
25
|
Adsorption and Bioactivity of Protein A on Silicon Surfaces Studied by AFM and XPS. J Colloid Interface Sci 2001; 233:180-189. [PMID: 11121264 DOI: 10.1006/jcis.2000.7240] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The adsorption of protein A on silicon surfaces was studied by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy. The deposition was made statically from various concentrations of protein A in water solution. The biological activity was checked by the immobilization of rabbit immunoglobulin G. The protein adsorption occurs in least two different phases and leads to a multilayer film. The first monolayer of proteins is rapidly adsorbed on the surface. The adsorption of the second layer of proteins occurs much more slowly (a thousand times slower) and also involves the third monolayer. The protein A of the first monolayer is denaturated and biologically inactive. On the contrary, the proteins of the second monolayer keep their natural diameter and remain biologically active. AFM artifacts such as the convolution with small objects and the resulting estimation of the coverage ratio are discussed. Copyright 2001 Academic Press.
Collapse
|
26
|
Magnetic properties of LaNi5and their variation with hydrogen absorption and desorption. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0305-4608/10/11/020] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
27
|
|
28
|
Ferromagnetic resonance in hydrogenated-dehydrogenated LaNi5, FeTi, and Mg2Ni and its relation to magnetic and surface investigations. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0305-4608/11/2/019] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
29
|
|
30
|
Variation of the order-disorder phase transition and of the magnetic ordering with deuterium concentration in CeDx(2.2⩽x⩽3.0). ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0022-3719/17/9/014] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
31
|
|
32
|
Evaluating mechanical adhesion of sol-gel titanium dioxide coatings containing calcium phosphate for metal implant application. Biomaterials 2000; 21:2193-201. [PMID: 10985493 DOI: 10.1016/s0142-9612(00)00160-5] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The adhesion of thin (< 10 microm) sol-gel calcium phosphate-titanium dioxide films bonded to a titanium substrate was studied using two different tests: a rotating-bending test and a tensile bond test. The former evaluates the impact of both the coating procedure and the surface pre-treatment on the resistance to fatigue of the substrate as well as the adhesion of the coating; the latter measures the tensile adhesion strength of the coating. Both tests gave similar results. A reduction of the thickness of the coating or an increase of the roughness of the substrate improves the quality of the interface. A comparison of the adhesion of the calcium phosphate-titanium dioxide film with that of a pure calcium phosphate coating obtained by a similar route suggests the involvement of a chemical component in the binding.
Collapse
|
33
|
Hydrogen atoms cause long-range electronic effects on graphite. PHYSICAL REVIEW LETTERS 2000; 84:4910-4913. [PMID: 10990829 DOI: 10.1103/physrevlett.84.4910] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/1999] [Indexed: 05/23/2023]
Abstract
We report on long-range electronic effects caused by hydrogen-carbon interaction at the graphite surface. Two types of defects could be distinguished with a combined mode of scanning tunneling microscopy and atomic force microscopy: chemisorption of hydrogen on the basal plane of graphite and atomic vacancy formation. Both types show a (sqrt[3]xsqrt[3])R30 degrees superlattice in the local density of states but have a different topographic structure. The range of modifications in the electronic structure, of fundamental importance for electronic devices based on carbon nanostructures, has been found to be of the order of 20-25 lattice constants.
Collapse
|
34
|
Surface and friction characterization by thermoelectric measurements during ultrasonic friction processes. ULTRASONICS 2000; 38:212-214. [PMID: 10829660 DOI: 10.1016/s0041-624x(99)00062-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Even though friction is one of the oldest problems in physics many aspects of friction processes are not clear today. We present an experimental setup, which permits the study of tribological systems by measuring the dissipated heat at the interface of two surfaces during a friction process with a time resolution of 1 ms. The apparatus is based on a standard ultrasonic wire-bond machine used in semiconductor industries to connect the internal semiconductor die to the external leads, but the standard bond wire is replaced by a thermocouple. To demonstrate the ability of the apparatus it will be shown that bond substrates used in semiconductor industries can be unequivocally characterized.
Collapse
|
35
|
|
36
|
Thin films of calcium phosphate and titanium dioxide by a sol-gel route: a new method for coating medical implants. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 1999; 10:161-167. [PMID: 15348164 DOI: 10.1023/a:1008985423644] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Titanium is a commonly used biomaterial for dental and orthopaedic applications. To increase its ability to bond with bone, some attempts were made to coat its surface with calcium phosphate (CaP). This paper describes a new type of coating. Instead of a pure CaP layer, a mixing of titanium dioxide (TIO2) and CaP is fabricated and deposited as a coating. These layers are deposited by a sol-gel route on pure titanium substrates using various pre-treatments. The method consists of mixing a solution of tetrabutyl ortho-titanate or a sol of titanium dioxide with a solution of calcium nitrate and phosphorous esters. This composite is deposited on to commercially pure titanium plates, mechanically polished or blasted with pure crystalline aluminum oxide, using the spin-coating technique. These coatings are then fired at 650 or 850 degrees C for various times. The samples are characterized by X-ray diffraction for their crystallinity, X-ray photoelectron spectroscopy for their surface chemical composition and scanning electron microscopy for their topography. Samples treated at 850 degrees C present a well-pronounced crystallinity, and a high chemical purity at the surface. The topography is strongly related to the viscosity of the precursor and the substrate pre-treatment. Possibilities to structure the outermost layer are presented.
Collapse
|
37
|
Electronic structure of high- and low- temperature c(2 x 2)-Na/Al(001) phases from angle-scanned ultraviolet photoemission. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:5893-5900. [PMID: 9986555 DOI: 10.1103/physrevb.54.5893] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
38
|
Orientation of adsorbed C60 molecules determined via x-ray photoelectron diffraction. PHYSICAL REVIEW LETTERS 1996; 76:4733-4736. [PMID: 10061367 DOI: 10.1103/physrevlett.76.4733] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
|
39
|
Experimental study of the valence-band region of Mg-Pd and Ba-Pd interfaces with and without hydrogen and of Mg and Ba hydrides. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 53:13808-13816. [PMID: 9983135 DOI: 10.1103/physrevb.53.13808] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
40
|
Final-state scattering in angle-resolved ultraviolet photoemission from copper. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 53:10209-10216. [PMID: 9982589 DOI: 10.1103/physrevb.53.10209] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
41
|
|
42
|
k-space mapping of majority and minority bands on the Fermi surface of Nickel below and above the Curie temperature. PHYSICAL REVIEW LETTERS 1996; 76:1150-1153. [PMID: 10061646 DOI: 10.1103/physrevlett.76.1150] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
|
43
|
Direct structure determination of a composite double-layer surface alloy by x-ray photoelectron diffraction: p(2 x 2)-Na/Al(111). PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:R2313-R2316. [PMID: 9981399 DOI: 10.1103/physrevb.52.r2313] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
44
|
Accuracy of alloy partial densities of states as determined by valence-band photoelectron diffraction. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:9497-9507. [PMID: 9977610 DOI: 10.1103/physrevb.51.9497] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
45
|
Quantitative evaluation of plasmon losses in thin magnesium films and its application to the thickness determination. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:7788-7795. [PMID: 9977362 DOI: 10.1103/physrevb.51.7788] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
46
|
|
47
|
Local structure of c(2 x 2)-Na on Al(001): Experimental evidence for the coexistence of intermixing and on-surface adsorption. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:14516-14524. [PMID: 9975674 DOI: 10.1103/physrevb.50.14516] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
48
|
KVV Auger-electron diffraction patterns from carbon solids. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 49:13820-13825. [PMID: 10010329 DOI: 10.1103/physrevb.49.13820] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
49
|
Complete Fermi surface mapping of Bi2Sr2CaCu2O8+x(001): Coexistence of short range antiferromagnetic correlations and metallicity in the same phase. PHYSICAL REVIEW LETTERS 1994; 72:2757-2760. [PMID: 10055969 DOI: 10.1103/physrevlett.72.2757] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
|
50
|
|