5,012 research outputs found
For post-statist geographies
This article critically investigates past and contemporary treatments of the state within geographical scholarship. We propose that there is a silent statism within geography that has shaped it in ways that limit geographical imaginations. Statism, herein, refers to a pervasive, historically contingent organisational logic that valourises and naturalises sovereign, coercive, and hierarchical relationships, within and beyond state spaces. We argue that although the explicit, colonial statism that characterised early geography is past, traces of statism nonetheless underpin much of the discipline. While political geography has increasingly critiqued ‘state-centrism’, we argue that it is essential to move beyond critique alone. Using anarchist state theory to critically build upon perspectives in geography, we argue that statism is intellectually and politically problematic and should be recast as an active constituent of unequal social relations. In turn, we outline five core myths that form its logical foundations. In concluding, three initial areas in which post-statist geographies can make inroads are identified: interrogating intersections between statism and other power relations; constructing post-statist epistemologies and methodologies; and addressing how the state is represented in geographical work
Complex Numbers, Quantum Mechanics and the Beginning of Time
A basic problem in quantizing a field in curved space is the decomposition of
the classical modes in positive and negative frequency. The decomposition is
equivalent to a choice of a complex structure in the space of classical
solutions. In our construction the real tunneling geometries provide the link
between the this complex structure and analytic properties of the classical
solutions in a Riemannian section of space. This is related to the Osterwalder-
Schrader approach to Euclidean field theory.Comment: 27 pages LATEX, UCSBTH-93-0
Analytical perturbative approach to periodic orbits in the homogeneous quartic oscillator potential
We present an analytical calculation of periodic orbits in the homogeneous
quartic oscillator potential. Exploiting the properties of the periodic
Lam{\'e} functions that describe the orbits bifurcated from the fundamental
linear orbit in the vicinity of the bifurcation points, we use perturbation
theory to obtain their evolution away from the bifurcation points. As an
application, we derive an analytical semiclassical trace formula for the
density of states in the separable case, using a uniform approximation for the
pitchfork bifurcations occurring there, which allows for full semiclassical
quantization. For the non-integrable situations, we show that the uniform
contribution of the bifurcating period-one orbits to the coarse-grained density
of states competes with that of the shortest isolated orbits, but decreases
with increasing chaoticity parameter .Comment: 15 pages, LaTeX, 7 figures; revised and extended version, to appear
in J. Phys. A final version 3; error in eq. (33) corrected and note added in
prin
Occurrence of periodic Lam\'e functions at bifurcations in chaotic Hamiltonian systems
We investigate cascades of isochronous pitchfork bifurcations of
straight-line librating orbits in some two-dimensional Hamiltonian systems with
mixed phase space. We show that the new bifurcated orbits, which are
responsible for the onset of chaos, are given analytically by the periodic
solutions of the Lam\'e equation as classified in 1940 by Ince. In Hamiltonians
with C_ symmetry, they occur alternatingly as Lam\'e functions of period
2K and 4K, respectively, where 4K is the period of the Jacobi elliptic function
appearing in the Lam\'e equation. We also show that the two pairs of orbits
created at period-doubling bifurcations of touch-and-go type are given by two
different linear combinations of algebraic Lam\'e functions with period 8K.Comment: LaTeX2e, 22 pages, 14 figures. Version 3: final form of paper,
accepted by J. Phys. A. Changes in Table 2; new reference [25]; name of
bifurcations "touch-and-go" replaced by "island-chain
Exact Solution of the Landau-Lifshitz Equations for a Radiating Charged Particle in The Coulomb Potential
We solve exactly the classical non-relativistic Landau-Lifshitz equations of
motion for a charged particle moving in a Coulomb potential, including
radiation damping. The general solution involves the Painleve transcendent of
type II. It confirms our physical intuition that a negatively charged classical
particle will spiral into the nucleus, supporting the the validity of the
Landau-Lifshitz equation.Comment: 2 figures; Figure added, also minor comments and correction
The effect of moderate intraoperative blood loss and norepinephrine therapy on sublingual microcirculatory perfusion in patients having open radical prostatectomy:An observational study
BACKGROUND: It is not clear whether moderate intraoperative blood loss and norepinephrine used to restore the macrocirculation impair the microcirculation and affect microcirculation/macrocirculation coherence. OBJECTIVE: We sought to investigate the effect of moderate intraoperative blood loss and norepinephrine therapy administered to treat intraoperative hypotension on the sublingual microcirculation. DESIGN: Prospective observational study. SETTING: University Medical Center Hamburg-Eppendorf, Hamburg, Germany, from November 2018 to March 2019. PATIENTS: Thirty patients scheduled for open radical prostatectomy and 29 healthy volunteer blood donors. INTERVENTION: Simultaneous assessment of the macrocirculation using a noninvasive finger-cuff method and the sublingual microcirculation using vital microscopy. MAIN OUTCOME MEASURES: The main outcome measures were changes in the sublingual microcirculation caused by moderate intraoperative blood loss and norepinephrine therapy. RESULTS: General anaesthesia decreased median [IQR] mean arterial pressure from 100 [90 to 104] to 79 [69 to 87] mmHg (P < 0.001), median heart rate from 69 [63 to 79] to 53 [44 to 62] beats per minute (P < 0.001), median cardiac index from 2.67 [2.42 to 3.17] to 2.09 [1.74 to 2.49] l min-1 m-2 (P < 0.001), and median microvascular flow index from 2.75 [2.66 to 2.85] to 2.50 [2.35 to 2.63] (P = 0.001). A median blood loss of 600 [438 to 913] ml until the time of prostate removal and norepinephrine therapy to treat intraoperative hypotension had no detrimental effect on the sublingual microcirculation: There were no clinically important changes in the microvascular flow index, the proportion of perfused vessels, the total vessel density, and the perfused vessel density. Blood donation resulted in no clinically important changes in any of the macrocirculatory or microcirculatory variables. CONCLUSION: Moderate intraoperative blood loss and norepinephrine therapy administered to treat intraoperative hypotension have no detrimental effect on the sublingual microcirculation and the coherence between the macrocirculation and microcirculation in patients having open radical prostatectomy
Separable triaxial potential-density pairs in MOND
We study mass models that correspond to MOND (triaxial) potentials for which
the Hamilton-Jacobi equation separates in ellipsoidal coordinates. The problem
is first discussed in the simpler case of deep-MOND systems, and then
generalized to the full MOND regime. We prove that the Kuzmin property for
Newtonian gravity still holds, i.e., that the density distribution of separable
potentials is fully determined once the density profile along the minor axis is
assigned. At variance with the Newtonian case, the fact that a positive density
along the minor axis leads to a positive density everywhere remains unproven.
We also prove that (i) all regular separable models in MOND have a vanishing
density at the origin, so that they would correspond to centrally dark-matter
dominated systems in Newtonian gravity; (ii) triaxial separable potentials
regular at large radii and associated with finite total mass leads to density
distributions that at large radii are not spherical and decline as ln(r)/r^5;
(iii) when the triaxial potentials admit a genuine Frobenius expansion with
exponent 0<epsilon<1, the density distributions become spherical at large
radii, with the profile ln(r)/r^(3+2epsilon). After presenting a suite of
positive density distributions associated with MOND separable potentials, we
also consider the important family of (non-separable) triaxial potentials V_1
introduced by de Zeeuw and Pfenniger, and we show that, as already known for
Newtonian gravity, they obey the Kuzmin property also in MOND. The ordinary
differential equation relating their potential and density along the z-axis is
an Abel equation of the second kind that, in the oblate case, can be explicitly
reduced to canonical form.Comment: 17 pages, 4 figures (low resolution), accepted by MNRA
Identifying a sublingual triangle as the ideal site for assessment of sublingual microcirculation
The sublingual mucosa is a commonly used intraoral location for identifying microcirculatory alterations using handheld vital microscopes (HVMs). The anatomic description of the sublingual cave and its related training have not been adequately introduced. The aim of this study was to introduce anatomy guided sublingual microcirculatory assessment. Measurements were acquired from the floor of the mouth using incident dark-field (IDF) imaging before (T0) and after (T1) sublingual cave anatomy instructed training. Instructions consists of examining a specific region of interested identified through observable anatomical structures adjacent and bilaterally to the lingual frenulum which is next to the sublingual papilla. The anatomical location called the sublingual triangle, was identified as stationed between the lingual frenulum, the sublingual fold and ventrally to the tongue. Small, large, and total vessel density datasets (SVD, LVD and TVD respectively) obtained by non-instructed and instructed measurements (NIN (T0) and IM (T1) respectively) were compared. Microvascular structures were analyzed, and the presence of salivary duct-related microcirculation was identified. A total of 72 video clips were used for analysis in which TVD, but not LVD and SVD, was higher in IM compared to NIM (NIM vs. IM, 25 ± 2 vs. 27 ± 3 mm/mm (p = 0.044), LVD NIM vs. IM: 7 ± 1 vs. 8 ± 1mm/mm (p = 0.092), SVD NIM vs. IM: 18 ± 2 vs. 20 ± 3 mm/mm (p = 0.103)). IM resulted in microcirculatory assessments which included morphological properties such as capillaries, venules and arterioles, without salivary duct-associated microcirculation. The sublingual triangle identified in this study showed consistent network-based microcirculation, without interference from microcirculation associated with specialized anatomic structures. These findings suggest that the sublingual triangle, an anatomy guided location, yielded sublingual based measurements that conforms with international guidelines. IM showed higher TVD values, and future studies are needed with larger sample sizes to prove differences in microcirculatory parameters
Cutaneous microcirculation in preterm neonates: comparison between sidestream dark field (SDF) and incident dark field (IDF) imaging
Incident dark field imaging (IDF) is a new generation handheld microscope for bedside visualization and quantification of microcirculatory alterations. IDF is the technical successor of sidestream dark field imaging (SDF), currently the most used device for microcirculatory measurements. In (pre)term neonates the reduced thickness of the skin allows non-invasive transcutaneous measurements. The goal of this study was to compare the existing device (SDF) and its technical successor (IDF) in preterm neonates. We hypothesized that IDF imaging produces higher quality images resulting in a higher vessel density. After written informed consent was given by the parents, skin microcirculation was consecutively measured on the inner upper arm with de SDF and IDF device. Images were exported and analyzed offline using existing software (AVA 3.0). Vessel density and perfusion were calculated using the total vessel density (TVD) proportion of perfused vessels (PPV) and perfused vessel density. The microcirculation images quality score was used to evaluate the quality of the video images. In a heterogeneous group of twenty preterm neonates (median GA 27.6 weeks, range 24–33.4) IDF imaging visualized 19.9 % more vessels resulting in a significantly higher vessel density (TVD 16.9 vs. 14.1/mm, p value < 0.001). The perfusion of vessels could be determined more accurately in the IDF images, resulting in a significant lower PPV (88.7 vs. 93.9 %, p value 0.002). The IDF video images scored optimal in a higher percentage compared to the SDF video images. IDF imaging of the cutaneous microcirculation in preterm neonates resulted in a higher vessel density and lower perfusion compared to the existing SDF device
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