410 research outputs found
Real world experience reflecting current guidelines
Background: In case of suspected acute coronary syndrome (ACS), international guidelines recommend to obtain a 12-lead ECG as soon as possible after first medical contact, to administrate platelet aggregation inhibitors and antithrombins, and to transfer the patient as quickly as possible to an emergency department.
Methods: A German emergency care service database was retrospectively analysed from 2014 to 2016. Data were tested for normal distribution and the Mann-Whitney test was used for statistical analysis. Results are presented as medians (IQR).
Results: A total of 1424 patients with suspected ACS were included in the present analysis. A 12-lead ECG was documented in 96% of patients (n = 1369). The prehospital incidence of ST-segment elevation myocardial infarction (STEMI) was 18% (n = 250). In 981 patients (69%), acetylsalicylic acid (ASA), unfractionated heparin (UFH), or ASA and UFH was given. Time in prehospital care differed significantly between non-STEMI (NSTEMI) ACS (37 [IQR 30, 44] min) and STEMI patients (33 [IQR 26, 40] min, n = 1395, p < 0.0001). Most of NSTEMI ACS and STEMI patients were brought to the emergency care unit, while 30% of STEMI patients were directly handed over to a cardiac catheterization laboratory.
Conclusions: Prehospital ECG helps to identify patients with STEMI, which occurs in 18% of suspected ACS. Patients without ST-elevations suffered from longer prehospital care times. Thus, it is tempting to speculate that ST-elevations in patients prompt prehospital medical teams to act more efficiently while the absence of ST-elevations even in patients with suspected ACS might cause unintended delays. Moreover, this analysis suggests the need for further efforts to make the cardiac catheterization laboratory the standard hand-over location for all STEMI patients.Einführung: Internationale Leitlinien empfehlen die umgehende Ableitung eines 12-Kanal-Elektrokardiogramms bei Patienten mit akuter Angina-pectoris-Symptomatik. Ebenfalls wird die präklinische Gabe von Azetylsalizylsäure, Heparin sowie der sofortige Transport in ein Krankenhaus mit der Möglichkeit einer koronarinvasiven Diagnostik empfohlen.
Methoden: Es wurden die Einsatzprotokolle einer Rettungsstellendatenbank retrospektiv für den Zeitraum von 2014–2016 auf diese Merkmale untersucht. Die Daten wurden auf Normalverteilung getestet und für die statistische Analyse wurde ein Mann-Whitney-Test verwendet. Die Ergebnisse sind als Mediane (Interquartilsabstand, IQR) dargestellt.
Ergebnisse: Es wurden 1424 Patienten mit Angina-pectoris-Symptomatik eingeschlossen. In 96 % (n = 1369) der Fälle wurde ein 12-Kanal-Elektrokardiogramm aufgezeichnet. Präklinisch wurden 250 Patienten (18 %) mit ST-Strecken-Hebungs-Infarkt (STEMI) diagnostiziert. Insgesamt 981 Patienten (69 %) erhielten Azetylsalizylsäure bzw. Heparin oder Azetylsalizylsäure und Heparin. Die präklinischen Zeiten unterschieden sich signifikant zwischen Patienten mit akutem Koronarsyndrom ohne Ischämiezeichen im Elektrokardiogramm (NSTEMI ACS; 37 min [IQR 30,44]) und Patienten mit ST-Hebungen (STEMI; 33 min [IQR 26,40]). Der Großteil der Patienten wurde in der Notaufnahme übergeben, während 30 % der STEMI-Patienten direkt in das Herzkatheterlabor transferiert wurden.
Schlussfolgerung: Die Inzidenz von ST-Hebungen liegt im präklinischen Bereich bei Patienten mit Angina-pectoris bei 18 %. Patienten ohne Ischämiezeichen wurden langsamer einem Krankenhaus zugeführt als Patienten mit STEMI. Dieses Ergebnis kann auf die geltenden Leitlinien zurückzuführen sein, da bei STEMI-Patienten die Zeit von Diagnosestellung bis zur koronarinvasiven Diagnostik <120 min betragen soll
Persistent currents through a quantum impurity: Protection through integrability
We consider an integrable model of a one-dimensional mesoscopic ring with the
conduction electrons coupled by a spin exchange to a magnetic impurity. A
symmetry analysis based on a Bethe Ansatz solution of the model reveals that
the current is insensitive to the presence of the impurity. We argue that this
is true for any integrable impurity-electron interaction, independent of choice
of physical parameters or couplings. We propose a simple physical picture of
how the persistent current gets protected by integrability.Comment: 5 pages, minor update
Kondo screening cloud effects in mesoscopic devices
We study how finite size effects may appear when a quantum dot in the Kondo
Coulomb blockade regime is embedded into a mesoscopic device with finite wires.
These finite size effects appear when the size of the mesoscopic device
containing the quantum dot is of the order of the size of Kondo cloud and
affect all thermodynamic and transport properties of the Kondo quantum dot. We
also generalize our results to the experimentally relevant case where the wires
contain several transverse modes/channels. Our results are based on
perturbation theory, Fermi liquid theory and slave boson mean field theory.Comment: 19 pages, 9 figure
Persistent Currents in the Heisenberg chain with a weak link
The Heisenberg chain with a weak link is studied, as a simple example of a
quantum ring with a constriction or defect. The Heisenberg chain is equivalent
to a spinless electron gas under a Jordan-Wigner transformation. Using density
matrix renormalization group and quantum Monte Carlo methods we calculate the
spin/charge stiffness of the model, which determines the strength of the
`persistent currents'. The stiffness is found to scale to zero in the weak link
case, in agreement with renormalization group arguments of Eggert and Affleck,
and Kane and Fisher.Comment: 14 pages, 7 figures, 2 tables, no changes to paper, author list
changed on archiv
Excited states in the twisted XXZ spin chain
We compute the finite size spectrum for the spin 1/2 XXZ chain with twisted
boundary conditions, for anisotropy in the regime , and
arbitrary twist . The string hypothesis is employed for treating
complex excitations. The Bethe Ansatz equtions are solved within a coupled
non-linear integral equation approach, with one equation for each type of
string. The root-of-unity quantum group invariant periodic chain reduces to the
XXZ_1/2 chain with a set of twist boundary conditions (,
an integer multiple of ). For this model, the restricted
Hilbert space corresponds to an unitary conformal field theory, and we recover
all primary states in the Kac table in terms of states with specific twist and
strings.Comment: 16 pages, Latex; added discussion on quantum group invariance and
arbitrary magnon numbe
Integrability of a t-J model with impurities
A t-J model for correlated electrons with impurities is proposed. The
impurities are introduced in such a way that integrability of the model in one
dimension is not violated. The algebraic Bethe ansatz solution of the model is
also given and it is shown that the Bethe states are highest weight states with
respect to the supersymmetry algebra gl(2/1)Comment: 14 page
Kondo Resonance in a Mesoscopic Ring Coupled to a Quantum Dot: Exact Results for the Aharonov-Bohm/Casher Effects
We study the persistent currents induced by both the Aharonov-Bohm and
Aharonov-Casher effects in a one-dimensional mesoscopic ring coupled to a
side-branch quantum dot at Kondo resonance. For privileged values of the
Aharonov-Bohm-Casher fluxes, the problem can be mapped onto an integrable
model, exactly solvable by a Bethe ansatz. In the case of a pure magnetic
Aharonov-Bohm flux, we find that the presence of the quantum dot has no effect
on the persistent current. In contrast, the Kondo resonance interferes with the
spin-dependent Aharonov-Casher effect to induce a current which, in the
strong-coupling limit, is independent of the number of electrons in the ring.Comment: Replaced with published version; 5 page
Interpreting Attoclock Measurements of Tunnelling Times
Resolving in time the dynamics of light absorption by atoms and molecules,
and the electronic rearrangement this induces, is among the most challenging
goals of attosecond spectroscopy. The attoclock is an elegant approach to this
problem, which encodes ionization times in the strong-field regime. However,
the accurate reconstruction of these times from experimental data presents a
formidable theoretical challenge. Here, we solve this problem by combining
analytical theory with ab-initio numerical simulations. We apply our theory to
numerical attoclock experiments on the hydrogen atom to extract ionization time
delays and analyse their nature. Strong field ionization is often viewed as
optical tunnelling through the barrier created by the field and the core
potential. We show that, in the hydrogen atom, optical tunnelling is
instantaneous. By calibrating the attoclock using the hydrogen atom, our method
opens the way to identify possible delays associated with multielectron
dynamics during strong-field ionization.Comment: 33 pages, 10 figures, 3 appendixe
Integrable impurities in Hubbard chain with the open boundary condition
The Kondo problem of two impurities in 1D strongly correlated electron system
within the framework of the open boundary Hubbard chain is solved and the
impurities, coupled to the ends of the electron system, are introduced by their
scattering matrices with electrons so that the boundary matrices satisfy the
reflecting integrability condition. The finite size correction of the ground
state energy is obtained due to the impurities. Exact expressions for the low
temperature specific heat contributed by the charge and spin parts of the
magnetic impurities are derived. The Pauli susceptibility and the Kondo
temperature are given explicitly. The Kondo temperature is inversely
proportional to the density of electrons.Comment: 6 pages, Revtex, To appear in Europhysics Letter
Prophylactic Treatment with Alkaline Phosphatase in Cardiac Surgery Induces Endogenous Alkaline Phosphatase Release
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