303 research outputs found
Physics of Polymorphic Transitions in CeRuSn
We report a detailed study of the polymorphic transitions in ternary stannide
CeRuSn on high quality single crystals through a combination of X-ray
diffraction experiments conducted at 300, 275 and 120 K, and measurements of
the thermal expansion, magnetization, and resistivity, along main
crystallographic axes. In addition, the transition was followed as a function
of pressure up to 0.8 GPa. The present X-ray diffraction data show that the
room temperature polymorph consists of the lattice doubled along the c axis
with respect to the CeCoAl-type structure consistent with previous reports.
Upon cooling, the compound undergoes two successive transitions, first to a
quintuple (290 K) and than to a triple CeCoAl superstructure at 225 K. The
transitions are accompanied by a tremendous volume change due to a strong
shrinking of the lattice along the c axis, which is clearly observed in thermal
expansion. We advance arguments that the volume collapse originates from an
increasing number of crystallographically inequivalent Ce sites and the change
of ratio between the short and long Ce-Ru bonds. The observed properties of the
polymorphic transition in CeRuSn are reminiscent of the transition in
elementary Cerium, suggesting that similar physics, i.e., a Kondo influenced
transition and strong lattice vibrations might be the driving forces
Predicting trajectories of behavioral adjustment in children diagnosed with acute lymphoblastic leukemia
Purpose
Previous research showed that children with cancer are at risk for developing behavioral adjustment problems after successful treatment; however, the course of adjustment remains unclear. This study focuses on adjustment trajectories of children during treatment for acute lymphoblastic leukemia (ALL) and aims to distinguish subgroups of patients showing different trajectories during active treatment, and to identify sociodemographic, medical, and psychosocial predictors of the distinct adjustment trajectories.
Methods
In a multicenter longitudinal study, 108 parents of a child (response rate 80 %) diagnosed with ALL were assessed during induction treatment (T0), after induction/consolidation treatment (T1), and after end of treatment (T2). Trajectories of child behavioral adjustment (Child Behavior Checklist; CBCL) were tested with latent class growth modeling (LCGM) analyses.
Results
For internalizing behavior, a three-trajectory model was found: a group that experienced no problems (60 %), a group that experienced only initial problems (30 %), and a group that experienced chronic problems (10 %). For externalizing behavior, a three-trajectory model was also found: a group that experienced no problems (83 %), a group that experienced chronic problems (12 %), and a group that experienced increasing problems (5 %). Only parenting stress and baseline QoL (cancer related) were found to contribute uniquely to adjustment trajectories.
Conclusions
The majority of the children (77 %) showed no or transient behavioral problems during the entire treatment as reported by parents. A substantial group (23 %) shows maladaptive trajectories of internalizing behavioral problems and/or externalizing behavioral problems. Screening for risk factors for developing problems might be helpful in early identification of these children
Basic Biomedical Sciences and the Future of Medical Education: Implications for Internal Medicine
The academic model of medical education in the United States is facing substantial challenges. Apprenticeship experiences with clinical faculty are increasingly important in most medical schools and residency programs. This trend threatens to separate clinical education from the scientific foundations of medical practice. Paradoxically, this devaluation of biomedical science is occurring as the ability to use new discoveries to rationalize clinical decision making is rapidly expanding. Understanding the scientific foundations of medical practice and the ability to apply them in the care of patients separates the physician from other health care professionals. The de-emphasis of biomedical science in medical education poses particular dangers for the future of internal medicine as the satisfaction derived from the application of science to the solving of a clinical problem has been a central attraction of the specialty. Internists should be engaged in the ongoing discussions of medical education reform and provide a strong voice in support of rigorous scientific training for the profession
Adjustment disorder in cancer patients after treatment:Prevalence and acceptance of psychological treatment
PURPOSE: To investigate the prevalence of adjustment disorder (AD) among cancer patients and the acceptance of psychological treatment, in relation to sociodemographic, clinical, and psychological factors. METHODS: Breast, prostate, and head and neck cancer patients of all stages and treatment modalities (N = 200) participated in this observational study. Patients completed the Hospital Anxiety and Depression Scale, Checklist Individual Strength, Distress Thermometer and problem list. Patients with increased risk on AD based on these questionnaires were scheduled for a diagnostic interview. Patients diagnosed with AD were invited to participate in a randomized controlled trial on the cost-effectiveness of psychological treatment. Participation in this trial was used as a proxy of acceptance of psychological treatment. Logistic regression analyses were used to investigate associated factors. RESULTS: The overall prevalence of AD was estimated at 13.1%. Sensitivity analyses showed prevalence rates of AD of 11.5%, 15.0%, and 23.5%. Acceptance of psychological treatment was estimated at 65%. AD was associated both with being employed (OR = 3.3, CI = 1.3–8.4) and having a shorter time since diagnosis (OR = 0.3, CI = 0.1–0.8). CONCLUSION: Taking sensitivity analysis into account, the prevalence of AD among cancer patients is estimated at 13 to 15%, and is related to being employed and having a shorter time since diagnosis. The majority of cancer patients with AD accept psychological treatment
The new heavy fermion compound CeBiNi
The family of cubic noncentrosymmetric 3-4-3 compounds has become a fertile
ground for the discovery of novel correlated metallic and insulating phases.
Here, we report the synthesis of a new heavy fermion compound,
CeBiNi. It is an isoelectronic analog of the prototypical Kondo
insulator CeBiPt and of the recently discovered Weyl-Kondo
semimetal CeBiPd. In contrast to the volume-preserving Pt-Pd
substitution, structural and chemical analyses reveal a positive chemical
pressure effect in CeBiNi relative to its heavier counterparts.
Based on the results of electrical resistivity, Hall effect, magnetic
susceptibility, and specific heat measurements, we identify an energy gap of
65-70 meV, about 8 times larger than that in CeBiPt and about 45
times larger than that of the Kondo-insulating background hosting the Weyl
nodes in CeBiPd. We show that this gap as well as other physical
properties do not evolve monotonically with increasing atomic number, i.e., in
the sequence CeBiNi-CeBiPd-CeBiPt, but
instead with increasing partial electronic density of states of the
orbitals at the Fermi energy. To understand under which condition topological
states form in these materials is a topic for future studies.Comment: 18 pages, 7 figure
Behavior of the Quantum Critical Point and the Fermi-liquid Domain in the Heavy Fermion Superconductor CeCoIn5 studied by resistivity
We report detailed very low temperature resistivity measurements on the heavy
fermion compounds Ce_{1-x}La_{x}CoIn5 (x=0 and x=0.01), with current applied in
two crystallographic directions [100] (basal plane) and [001] (perpendicular to
the basal plane) under magnetic field applied in the [001] or [011] direction.
We found a Fermi liquid (\rho \propto T^{2}) ground state, in all cases, for
fields above the superconducting upper critical field. We discuss the possible
location of a field induced quantum critical point with respect to Hc2(0), and
compare our measurements with the previous reports in order to give a clear
picture of the experimental status on this long debated issue.Comment: 17 pages, 7 figures accepted for publication in JPS
Microtubule configurations and nuclear DNA synthesis during initiation of suspensor-bearing embryos from Brassica napus cv. Topas microspores
In the new Brassica napus microspore culture system, wherein embryos with suspensors are formed, ab initio mimics zygotic embryogenesis. The system provides a powerful in vitro tool for studying the diverse developmental processes that take place during early stages of plant embryogenesis. Here, we studied in this new culture system both the temporal and spatial distribution of nuclear DNA synthesis places and the organization of the microtubular (MT) cytoskeleton, which were visualized with a refined whole mount immunolocalization technology and 3D confocal laser scanning microscopy. A ‘mild’ heat stress induced microspores to elongate, to rearrange their MT cytoskeleton and to re-enter the cell cycle and perform a predictable sequence of divisions. These events led to the formation of a filamentous suspensor-like structure, of which the distal tip cell gave rise to the embryo proper. Cells of the developing pro-embryo characterized endoplasmic (EMTs) and cortical microtubules (CMTs) in various configurations in the successive stages of the cell cycle. However, the most prominent changes in MT configurations and nuclear DNA replication concerned the first sporophytic division occurring within microspores and the apical cell of the pro-embryo. Microspore embryogenesis was preceded by pre-prophase band formation and DNA synthesis. The apical cell of the pro-embryo exhibited a random organization of CMTs and, in relation to this, isotropic expansion occurred, mimicking the development of the apical cell of the zygotic situation. Moreover, the apical cell entered the S phase shortly before it divided transversally at the stage that the suspensor was 3–8 celled
Adaptation of the Landau-Migdal Quasiparticle Pattern to Strongly Correlated Fermi Systems
A quasiparticle pattern advanced in Landau's first article on Fermi liquid
theory is adapted to elucidate the properties of a class of strongly correlated
Fermi systems characterized by a Lifshitz phase diagram featuring a quantum
critical point (QCP) where the density of states diverges. The necessary
condition for stability of the Landau Fermi Liquid state is shown to break down
in such systems, triggering a cascade of topological phase transitions that
lead, without symmetry violation, to states with multi-connected Fermi
surfaces. The end point of this evolution is found to be an exceptional state
whose spectrum of single-particle excitations exhibits a completely flat
portion at zero temperature. Analysis of the evolution of the temperature
dependence of the single-particle spectrum yields results that provide a
natural explanation of classical behavior of this class of Fermi systems in the
QCP region.Comment: 26 pages, 14 figures. Dedicated to 100th anniversary of A.B.Migdal
birthda
Quasiparticles of strongly correlated Fermi liquids at high temperatures and in high magnetic fields
Strongly correlated Fermi systems are among the most intriguing, best
experimentally studied and fundamental systems in physics. There is, however,
lack of theoretical understanding in this field of physics. The ideas based on
the concepts like Kondo lattice and involving quantum and thermal fluctuations
at a quantum critical point have been used to explain the unusual physics.
Alas, being suggested to describe one property, these approaches fail to
explain the others. This means a real crisis in theory suggesting that there is
a hidden fundamental law of nature. It turns out that the hidden fundamental
law is well forgotten old one directly related to the Landau---Migdal
quasiparticles, while the basic properties and the scaling behavior of the
strongly correlated systems can be described within the framework of the
fermion condensation quantum phase transition (FCQPT). The phase transition
comprises the extended quasiparticle paradigm that allows us to explain the
non-Fermi liquid (NFL) behavior observed in these systems. In contrast to the
Landau paradigm stating that the quasiparticle effective mass is a constant,
the effective mass of new quasiparticles strongly depends on temperature,
magnetic field, pressure, and other parameters. Our observations are in good
agreement with experimental facts and show that FCQPT is responsible for the
observed NFL behavior and quasiparticles survive both high temperatures and
high magnetic fields.Comment: 17 pages, 17 figures. Dedicated to 100th anniversary of A.B.Migdal
birthda
Prospective longitudinal study on fear of cancer recurrence in patients newly diagnosed with head and neck cancer:Course, trajectories, and associated factors
Background: This study assessed the course of fear of cancer recurrence (FCR) in patients newly diagnosed with head and neck cancer (HNC), identified FCR trajectories and factors associated with FCR trajectories. Methods: Six hundred and seventeen HNC patients from the NET-QUBIC cohort study completed the Cancer Worry Scale-6 at diagnosis, 3 and 6 months post-treatment. FCR trajectories were identified using Latent Class Growth Analysis. Associations were explored between FCR trajectories and baseline demographic and medical variables, coping and self-efficacy. Results: Overall, FCR decreased slightly between baseline and 3 months post-treatment and remained stable up to 6 months. Two FCR trajectories were identified: “high stable” (n = 125) and “low declining” (n = 492). Patients with high stable FCR were younger, reported more negative adjustment, passive coping, and reassuring thoughts, and less avoidance. Conclusions: The majority of HNC patients have low declining FCR after diagnosis, but one in five patients experience persistent high FCR up to 6 months post-treatment
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