| 1. |
- Enkovaara, J., et al.
(författare)
-
Electronic structure calculations with GPAW : a real-space implementation of the projector augmented-wave method
- 2010
-
Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 22:25, s. 253202-
-
Forskningsöversikt (refereegranskat)abstract
- Electronic structure calculations have become an indispensable tool in many areas of materials science and quantum chemistry. Even though the Kohn-Sham formulation of the density-functional theory (DFT) simplifies the many-body problem significantly, one is still confronted with several numerical challenges. In this article we present the projector augmented-wave (PAW) method as implemented in the GPAW program package (https://wiki.fysik.dtu.dk/gpaw) using a uniform real-space grid representation of the electronic wavefunctions. Compared to more traditional plane wave or localized basis set approaches, real-space grids offer several advantages, most notably good computational scalability and systematic convergence properties. However, as a unique feature GPAW also facilitates a localized atomic-orbital basis set in addition to the grid. The efficient atomic basis set is complementary to the more accurate grid, and the possibility to seamlessly switch between the two representations provides great flexibility. While DFT allows one to study ground state properties, time-dependent density-functional theory (TDDFT) provides access to the excited states. We have implemented the two common formulations of TDDFT, namely the linear-response and the time propagation schemes. Electron transport calculations under finite-bias conditions can be performed with GPAW using non-equilibrium Green functions and the localized basis set. In addition to the basic features of the real-space PAW method, we also describe the implementation of selected exchange-correlation functionals, parallelization schemes, Delta SCF-method, x-ray absorption spectra, and maximally localized Wannier orbitals.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Conley, Kevin M., et al.
(författare)
-
Plasmon Excitations in Mixed Metallic Nanoarrays
- 2019
-
Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 13:5, s. 5344-5355
-
Tidskriftsartikel (refereegranskat)abstract
- © 2019 American Chemical Society. Features of the surface plasmon from macroscopic materials emerge in molecular systems, but differentiating collective excitations from single-particle excitations in molecular systems remains elusive. The rich interactions between single-particle electron-hole and collective electron excitations produce phenomena related to the chemical physics aspects within the atomic array. We study the plasmonic properties of atomic arrays of noble (Au, Ag, and Cu) and transition-metal (Pd, Pt) homonuclear chains using time-dependent density functional theory and their Kohn-Sham transition contributions. The response to the electromagnetic radiation is related to both the geometry-dependent confinement of sp-valence electrons and the energy position of d-electrons in the different atomic species and the hybridization between d and sp electrons. It is possible to tune the position of the plasmon resonance, split it into several peaks, and eventually achieve broadband absorption of radiation. Arrays of mixed noble and transition-metal chains may have strongly attenuated plasmonic behavior. The collective nature of the excitations is ascertained using their Kohn-Sham transition contributions. To manipulate the plasmonic response and achieve the desired properties for broad applications, it is vital to understand the origins of these phenomena in atomic chains and their arrays.
|
|
| 5. |
- Dyson, Kylie, et al.
(författare)
-
International variation in survival after out-of-hospital cardiac arrest : A validation study of the Utstein template.
- 2019
-
Ingår i: Resuscitation. - : Elsevier BV. - 0300-9572 .- 1873-1570. ; 138, s. 168-181
-
Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: Out-of-hospital cardiac arrest (OHCA) survival varies greatly between communities. The Utstein template was developed and promulgated to improve the comparability of OHCA outcome reports, but it has undergone limited empiric validation. We sought to assess how much of the variation in OHCA survival between emergency medical services (EMS) across the globe is explained by differences in the Utstein factors. We also assessed how accurately the Utstein factors predict OHCA survival.METHODS: We performed a retrospective analysis of patient-level prospectively collected data from 12 OHCA registries from 12 countries for the period 1 Jan 2006 through 31 Dec 2011. We used generalized linear mixed models to examine the variation in survival between EMS agencies (n=232).RESULTS: Twelve registries contributed 86,759 cases. Patient arrest characteristics, EMS treatment and patient outcomes varied across registries. Overall survival to hospital discharge was 10% (range, 6% to 22%). Overall survival with Cerebral Performance Category of 1 or 2 (available for 8/12 registries) was 8% (range, 2% to 20%). The area-under-the-curve for the Utstein model was 0.85 (Wald CI: 0.85-0.85). The Utstein factors explained 51% of the EMS agency variation in OHCA survival.CONCLUSIONS: The Utstein factors explained 51% of the variation in survival to hospital discharge among multiple large geographically separate EMS agencies. This suggests that quality improvement and public health efforts should continue to target modifiable Utstein factors to improve OHCA survival. Further study is required to identify the reasons for the variation that is incompletely understood.
|
|
| 6. |
- Herlitz, Johan, et al.
(författare)
-
Resuscitation in Europe : a Tale of five European Regions
- 1999
-
Ingår i: Resuscitation. - : Elsevier Ireland Ltd. - 0300-9572 .- 1873-1570. ; 41:2, s. 121-131
-
Tidskriftsartikel (refereegranskat)abstract
- Aim: To describe cardiac arrest data from five emergency medical services (EMS) systems in Europe with regard to survival from an out-of-hospital cardiac arrest. Methods: Based on recommendations from various countries in Europe EMS systems were approached with regard to survival from out-of-hospital cardiac arrest. Five EMS systems were asked to report their cardiac arrest data according to the Utstein style. Results: The five selected EMS systems were: Bonn (Germany), Göttingen (Germany), Helsinki (Finland), Reykjavik (Iceland) and Stavanger (Norway). For patients with a bystander witnessed arrest of cardiac aetiology the percentage of patients being discharged alive from hospital in these regions were: 21, 33, 23, 23 and 35. The corresponding percentages for patients fulfilling criteria as above and being found in ventricular fibrillation were: 32, 42, 32, 27 and 55. Conclusions: Many EMS systems in Europe show extremely good results in terms of survival after an out-of-hospital cardiac arrest. Some of the results should be interpreted with caution since they were based on relatively small sample sizes. Furthermore, the results from one of the regions (Stavanger) was unit based and not community based.
|
|
| 7. |
- Mattila, O. S., et al.
(författare)
-
Targets for improving dispatcher identification of acute stroke
- 2019
-
Ingår i: International Journal of Stroke. - : SAGE Publications. - 1747-4930 .- 1747-4949. ; 14:4, s. 409-416
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Accurate identification of acute stroke by Emergency Medical Dispatchers (EMD) is essential for timely and purposeful deployment of Emergency Medical Services (EMS), and a prerequisite for operating mobile stroke units. However, precision of EMD stroke recognition is currently modest. Aims: We sought to identify targets for improving dispatcher stroke identification. Methods: Dispatch codes and EMS patient records were cross-linked to investigate factors associated with an incorrect dispatch code in a prospective observational cohort of 625 patients with a final diagnosis of acute stroke or transient ischemic attack (TIA), transported to our stroke center as candidates for recanalization therapies. Call recordings were analyzed in a subgroup that received an incorrect low-priority dispatch code indicating a fall or unknown acute illness (n = 46). Results: Out of 625 acute stroke/TIA patients, 450 received a high-priority stroke dispatch code (sensitivity 72.0%; 95% CI, 68.5-75.5). Independent predictors of dispatcher missed acute stroke included a bystander caller (aOR, 3.72; 1.48-9.34), confusion (aOR, 2.62; 1.59-4.31), fall at onset (aOR, 1.86; 1.24-2.78), and older age (aOR [per year], 1.02; 1.01-1.04). Of the analyzed call recordings, 71.7% revealed targets for improvement, including failure to recognize a Face Arm Speech Time (FAST) test symptom (21/46 cases, 18 with speech disturbance), or failure to thoroughly evaluate symptoms (12/46 cases). Conclusions: Based on our findings, efforts to improve dispatcher stroke identification should primarily focus on improving recognition of acute speech disturbance, and implementing screening of FAST-symptoms in emergency phone calls revealing a fall or confusion.
|
|
| 8. |
- Mattila, O S, et al.
(författare)
-
Ultra-acute diagnostics for stroke: Large-scale implementation of prehospital biomarker sampling.
- 2017
-
Ingår i: Acta neurologica Scandinavica. - : Hindawi Limited. - 1600-0404 .- 0001-6314. ; 136:1, s. 17-23
-
Tidskriftsartikel (refereegranskat)abstract
- Blood-based biomarkers could enable early and cost-effective diagnostics for acute stroke patients in the prehospital setting to support early initiation of treatments. To facilitate development of ultra-acute biomarkers, we set out to implement large-scale prehospital blood sampling and determine feasibility and diagnostic timesavings of this approach.Emergency medical services (EMS) personnel of the Helsinki metropolitan area were trained to collect prehospital blood samples from thrombolysis candidates using a cannula adapter technique. Time delays, sample quality, and logistics were investigated between May 20, 2013 and May 19, 2014.Prehospital blood sampling and study recruiting were successfully performed for 430 thrombolysis candidates, of which 50% had ischemic stroke, 14.4% TIA, 13.5% hemorrhagic stroke, and 22.1% stroke mimics. A total of 66.3% of all samples were collected during non-office hours. The median (interquartile range) emergency call to prehospital sample time was 33minutes (25-41), and the median time from reported symptom onset or wake-up to prehospital sample was 53minutes (38-85; n=394). Prehospital sampling was performed 31minutes (25-42) earlier than hospital admission blood sampling and 37minutes (30-47) earlier than admission neuroimaging. Hemolysis rate in serum and plasma samples was 6.5% and 9.3% for EMS samples, and 0.7% and 1.6% for admission samples.Prehospital biomarker sampling can be implemented in all EMS units and provides a median timesaving of more than 30minutes to first blood sample. Large prehospital sample sets will enable development of novel ambulance biomarkers to improve early differential diagnosis and treatment of thrombolysis candidates.
|
|
| 9. |
- Mattila, O. S., et al.
(författare)
-
Ultra-Early Differential Diagnosis of Acute Cerebral Ischemia and Hemorrhagic Stroke by Measuring the Prehospital Release Rate of GFAP
- 2021
-
Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 67:10, s. 1361-1372
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Plasma glial fibrillary acidic protein (GFAP) and tau are promising markers for differentiating acute cerebral ischemia (ACI) and hemorrhagic stroke (HS), but their prehospital dynamics and usefulness are unknown. METHODS: We performed ultra-sensitivite single-molecule array (Simoa((R))) measurements of plasma GFAP and total tau in a stroke code patient cohort with cardinal stroke symptoms [National Institutes of Health Stroke Scale (NIHSS) >= 3]. Sequential sampling included 2 ultra-early samples, and a follow-up sample on the next morning. RESULTS: We included 272 cases (203 ACI, 60 HS, and 9 stroke mimics). Median (IQR) last-known-well to sampling time was 53 (35-90) minutes for initial prehospital samples, 90 (67-130) minutes for secondary acute samples, and 21 (16-24) hours for next morning samples. Plasma GFAP was significantly higher in patients with HS than ACI (P<0.001 for <1hour and <3hour prehospital samples, and <3hour secondary samples), while total tau showed no intergroup difference. The prehospital GFAP release rate (pg/mL/minute) occurring between the 2 very early samples was significantly higher in patients with HS than ACI [2.4 (0.6-14.1)] versus 0.3 (-0.3-0.9)pg/mL/minute, P<0.001. For cases with <3hour prehospital sampling (ACI n=178, HS n=59), a combined rule (prehospital GFAP >410pg/mL, or prehospital GFAP 90-410pg/mL together with GFAP release >0.6pg/mL/minute) enabled ruling out HS with high certainty (NPV 98.4%) in 68% of patients with ACI (sensitivity for HS 96.6%, specificity 68%, PPV 50%). CONCLUSIONS: In comparison to single-point measurement, monitoring the prehospital GFAP release rate improves ultra-early differentiation of stroke subtypes. With serial measurement GFAP has potential to improve future prehospital stroke diagnostics.
|
|
| 10. |
- Nishiyama, C, et al.
(författare)
-
Apples to apples or apples to oranges? International variation in reporting of process and outcome of care for out-of-hospital cardiac arrest
- 2014
-
Ingår i: Resuscitation. - : Elsevier Ireland Ltd.. - 0300-9572 .- 1873-1570. ; 85:11, s. 1599-1609
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Survival after out-of-hospital cardiac arrest (OHCA) varies between communities, due in part to variation in the methods of measurement. The Utstein template was disseminated to standardize comparisons of risk factors, quality of care, and outcomes in patients with OHCA. We sought to assess whether OHCA registries are able to collate common data using the Utstein template. A subsequent study will assess whether the Utstein factors explain differences in survival between emergency medical services (EMS) systems. STUDY DESIGN: Retrospective study. SETTING: This retrospective analysis of prospective cohorts included adults treated for OHCA, regardless of the etiology of arrest. Data describing the baseline characteristics of patients, and the process and outcome of their care were grouped by EMS system, de-identified, and then collated. Included were core Utstein variables and timed event data from each participating registry. This study was classified as exempt from human subjects' research by a research ethics committee. MEASUREMENTS AND MAIN RESULTS: Thirteen registries with 265 first-responding EMS agencies in 13 countries contributed data describing 125,840 cases of OHCA. Variation in inclusion criteria, definition, coding, and process of care variables were observed. Contributing registries collected 61.9% of recommended core variables and 42.9% of timed event variables. Among core variables, the proportion of missingness was mean 1.9±2.2%. The proportion of unknown was mean 4.8±6.4%. Among time variables, missingness was mean 9.0±6.3%. CONCLUSIONS: International differences in measurement of care after OHCA persist. Greater consistency would facilitate improved resuscitation care and comparison within and between communities.
|
|
