850 research outputs found
Superconductivity of Quasi-One and Quasi-Two Dimensional Tight-Binding Electrons in Magnetic Field
The upper critical field of the tight-binding electrons in the
three-dimensional lattice is investigated.
The electrons make Cooper pairs between the eigenstates with the same energy
in the strong magnetic field. The transition lines in the quasi-one dimensional
case are shown to deviate from the previously obtained results where the
hopping matrix elements along the magnetic field are neglected. In the absence
of the Pauli pair breaking the transition temperature of the quasi-two
dimensional electrons is obtained to oscillationally increase as the magnetic
field becomes large and reaches to in the strong field as in the
quasi-one dimensional case.Comment: 4pages,4figures,to be published in J.Phys.Soc.Jp
Barriers to symptom management care pathway implementation in pediatric cancer
BACKGROUND: Objectives were to describe barriers to pediatric cancer symptom management care pathway implementation and the impact of the COVID-19 pandemic on clinical research evaluating their implementation.
METHODS: We included 25 pediatric oncology hospitals in the United States that supported a grant submission to perform a cluster randomized trial in which the intervention encompassed care pathways for symptom management. A survey was distributed to site principal investigators prior to randomization to measure contextual elements related to care pathway implementation. Questions included the inner setting measures of the Consolidated Framework for Implementation Research (CFIR), study-specific potential barriers and the impact of the COVID-19 pandemic on clinical research. The Wilcoxon rank sum test was used to compare characteristics of institutions that agreed that their department supported the implementation of symptom management care pathways vs. institutions that did not agree.
RESULTS: Of the 25 sites, one withdrew because of resource constraints and one did not respond, leaving 23 institutions. Among the seven CFIR constructs, the least supported was implementation climate; 57% agreed there was support, 39% agreed there was recognition and 39% agreed there was prioritization for symptom management care pathway implementation at their institution. Most common barriers were lack of person-time to create care pathways and champion their use (35%), lack of interest from physicians (30%) and lack of information technology resources (26%). Most sites reported no negative impact of the COVID-19 pandemic across research activities. Sites with fewer pediatric cancer patients were more likely to agree that staff are supported to implement symptom management care pathways (P = 0.003).
CONCLUSIONS: The most commonly reported barriers to implementation were lack of support, recognition and prioritization. The COVID-19 pandemic may not be a major barrier to clinical research activities in pediatric oncology
Weak Field Magnetoresistance in Quasi-One-Dimensional Systems
Theoretical studies are presented on weak localization effects and
magnetoresistance in quasi-one-dimensional systems with open Fermi surfaces.
Based on the Wigner representation, the magnetoresistance in the region of weak
field has been studied for five possible configurations of current and field
with respect to the one-dimensional axis. It has been indicated that the
anisotropy and its temperature dependences of the magnetoresistance will give
information on the degree of one-dimensionality and the phase relaxation time.Comment: pages 11, LaTeX, 5 figures, uses jpsj.sty. To be published in J.
Phys. Soc. Jpn. (Vol.67(1998) No.4); Added some references and a Note at Feb.
13 199
Pharmacokinetic Disposition and Clinical Outcomes in Infants and Children Receiving Intravenous Busulfan for Allogeneic Hematopoietic Stem Cell Transplantation
AbstractWe conducted a retrospective pharmacokinetic analysis of i.v. busulfan in children undergoing hematopoietic stem cell transplantation (HSCT) and describe its relation to transplantation outcomes. Forty-five children (median age, 3 yr) underwent HSCT at The Hospital for Sick Children from April 2003 through January 2006 and received i.v. busulfan every 6 h as part of their conditioning regimen. Initial busulfan doses were based on actual patient weight: <9 kg, 0.95 mg/kg per dose; 9-16 kg, 1.2 mg/kg per dose; 16-23 kg, 1.1 mg/kg per dose; 24-34 kg, 0.95 mg/kg per dose; >34 kg, 0.8 mg/kg per dose. Plasma busulfan concentrations were obtained after the first dose. The fourth and subsequent busulfan doses were adjusted to achieve an area under the concentration versus time curve (AUC) of 900-1500 μM·min. Development of hepatic venous occlusive disease (HVOD; modified Baltimore criteria) and engraftment (absolute neutrophil count ≥0.5 × 109/L) were evaluated. Busulfan pharmacokinetic parameters were calculated using 1-compartment methods. Mean busulfan pharmacokinetic parameters were maximum concentration (Cmax; 4.7 ± 0.75 μM), volume of distribution at steady state (0.68 ± 0.17 L/kg), elimination rate constant (0.0051 ± 0.0010 min−1), total body clearance (3.5 ± 1.23 mL/[min·kg]), and AUC (1271 ± 280 μM·min). Mean volume of distribution at steady state was larger in children <1 yr of age (0.77 ± 0.24 vs 0.64 ± 0.11 L/kg; P = .040) and children <4 yr of age (0.73 ± 0.18 vs 0.60 ± 0.11 L/kg; P = .001) than in older children. Compared with older children, mean weight-adjusted total body clearance was higher in children <4 yr of age (3.8 ± 1.40 versus 3.0 ± 0.76 mL/[min·kg]). HVOD was diagnosed in 8 children (18%), including 4 children <1 yr of age. Children who developed HVOD achieved a lower Cmax than did those without HVOD (4.2 ± 0.68 versus 4.8 ± 0.73 μM; P = .035). Other than Cmax, no association was observed between busulfan disposition and development of HVOD in children for whom i.v. busulfan doses were adjusted to achieve a target AUC. The influence of factors other than busulfan disposition on transplantation outcomes, such as genetic polymorphisms, should be evaluated
Guideline for the Prevention of Oral and Oropharyngeal Mucositis in Children Receiving Treatment for Cancer or Undergoing Haematopoietic Stem Cell Transplantation
PURPOSE: To develop an evidence-based clinical practice guideline for the prevention of oral mucositis in children (0-18 years) receiving treatment for cancer or undergoing haematopoietic stem cell transplantation (HSCT).
METHODS: The Mucositis Prevention Guideline Development Group was interdisciplinary and included internationally recognised experts in paediatric mucositis. For the evidence review, we included randomised controlled trials (RCTs) conducted in either children or adults evaluating the following interventions selected according to prespecified criteria: cryotherapy, low level light therapy (LLLT) and keratinocyte growth factor (KGF). We also examined RCTs of any intervention conducted in children. For all systematic reviews, we synthesised the occurrence of severe oral mucositis. The Grades of Recommendation, Assessment, Development and Evaluation approach was used to describe quality of evidence and strength of recommendations.
RESULTS: We suggest cryotherapy or LLLT may be offered to cooperative children receiving chemotherapy or HSCT conditioning with regimens associated with a high rate of mucositis. We also suggest KGF may be offered to children receiving HSCT conditioning with regimens associated with a high rate of severe mucositis. However, KGF use merits caution as there is a lack of efficacy and toxicity data in children, and a lack of long-term follow-up data in paediatric cancers. No other interventions were recommended for oral mucositis prevention in children.
CONCLUSIONS: All three specific interventions evaluated in this clinical practice guideline were associated with a weak recommendation for use. There may be important organisational and cost barriers to the adoption of LLLT and KGF. Considerations for implementation and key research gaps are highlighted
Effective theory for the Goldstone field in the BCS-BEC crossover at T=0
We perform a detailed study of the effective Lagrangian for the Goldstone
mode of a superfluid Fermi gas at zero temperature in the whole BCS-BEC
crossover. By using a derivative expansion of the response functions, we derive
the most general form of this Lagrangian at the next to leading order in the
momentum expansion in terms of four coefficient functions. This involves the
elimination of all the higher order time derivatives by careful use of the
leading order field equations. In the infinite scattering length limit where
conformal invariance is realized, we show that the effective Lagrangian must
contain an unnoticed invariant combination of higher spatial gradients of the
Goldstone mode, while explicit couplings to spatial gradients of the trapping
potential are absent. Across the whole crossover, we determine all the
coefficient functions at the one-loop level, taking into account the dependence
of the gap parameter on the chemical potential in the mean-field approximation.
These results are analytically expressed in terms of elliptic integrals of the
first and second kind. We discuss the form of these coefficients in the extreme
BCS and BEC regimes and around the unitary limit, and compare with recent work
by other authors.Comment: 27 pages. 4 references added, typos corrected, expanded Section III
Dimensional Crossover of Weak Localization in a Magnetic Field
We study the dimensional crossover of weak localization in strongly
anisotropic systems. This crossover from three-dimensional behavior to an
effective lower dimensional system is triggered by increasing temperature if
the phase coherence length gets shorter than the lattice spacing . A similar
effect occurs in a magnetic field if the magnetic length becomes shorter
than , where \D_{||}/D_\perp is the ratio of the
diffusion coefficients parallel and perpendicular to the planes or chains.
depends on the direction of the magnetic field, e.g. or
1/2 for a magnetic field parallel or perpendicular to the planes in a quasi
two-dimensional system. We show that even in the limit of large magnetic field,
weak localization is not fully suppressed in a lattice system. Experimental
implications are discussed in detail.Comment: RevTeX, 11 pages, 4 figures; three references added and discusse
Phase Fluctuations and Vortex Lattice Melting in Triplet Quasi-One-Dimensional Superconductors at High Magnetic Fields
Assuming that the order parameter corresponds to an equal spin triplet
pairing symmetry state, we calculate the effect of phase fluctuations in
quasi-one-dimensional superconductors at high magnetic fields applied along the
y (b') axis. We show that phase fluctuations can destroy the theoretically
predicted triplet reentrant superconducting state, and that they are
responsible for melting the magnetic field induced Josephson vortex lattice
above a magnetic field dependent melting temperature Tm.Comment: 4 pages (double column), 1 eps figur
Possible Triplet Electron Pairing and an Anisotropic Spin Susceptibility in Organic Superconductors (TMTSF)_2 X
We argue that (TMTSF)_2 PF_6 compound under pressure is likely a triplet
superconductor with a vector order parameter d(k) \equiv (d_a(k) \neq 0, d_c(k)
= ?, d_{b'}(k) = 0); |d_a(k)| > |d_c(k)|. It corresponds to an anisotropic spin
susceptibility at T=0: \chi_{b'} = \chi_0, \chi_a \ll \chi_0, where \chi_0 is
its value in a metallic phase. [The spin quantization axis, z, is parallel to a
so-called b'-axis]. We show that the suggested order parameter explains why the
upper critical field along the b'-axis exceeds all paramagnetic limiting
fields, including that for a nonuniform superconducting state, whereas the
upper critical field along the a-axis (a \perp b') is limited by the Pauli
paramagnetic effects [I. J. Lee, M. J. Naughton, G. M. Danner and P. M.
Chaikin, Phys. Rev. Lett. 78, 3555 (1997)]. The triplet order parameter is in
agreement with the recent Knight shift measurements by I. J. Lee et al. as well
as with the early results on a destruction of superconductivity by nonmagnetic
impurities and on the absence of the Hebel-Slichter peak in the NMR relaxation
rate.Comment: 4 pages, 1 eps figur
Structure of the Fulde-Ferrell-Larkin-Ovchinnikov state in two-dimensional superconductors
Nonuniform superconducting state due to strong spin magnetism is studied in
two-dimensional type-II superconductors near the second order phase transition
line between the normal and the superconducting states. The optimum spatial
structure of the orderparameter is examined in systems with cylindrical
symmetric Fermi surfaces. It is found that states with two-dimensional
structures have lower free energies than the traditional one-dimensional
solutions, at low temperatures and high magnetic fields. For s-wave pairing,
triangular, square, hexagonal states are favored depending on the temperature,
while square states are favored at low temperatures for d-wave pairing. In
these states, orderparameters have two-dimensional structures such as square
and triangular lattices.Comment: 11 pages (LaTeX, revtex.sty), 3 figures; added reference
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