Quantum Effects in the Spin Dynamics of the Linear Heisenberg Antiferromagnet

We present an approximate analytic expression for the dynamical spin correlation function of the S=1/2 linear Heisenberg antiferromagnet at T=0. The basis for our approach is that in zero field the spectrum is dominated by a double continuum [in (q,ω) ‐space] of triplet spin waveexcitations. The S=1/2 integrated intensity agrees very well with recent neutron scattering results on CPC, unlike the corresponding classical intensity. Moreover, the S=1/2 spectral weight function shows increasing asymmetry as q→π, a quantum effect, observable in more recent neutron scattering data. In non‐zero magnetic field, there exist two, partly overlapping, double continua, each giving rise to a peak situated at the lower boundary. The (zz component of) spectral weight function therefore has a double‐peaked structure, as observed experimentally. Theory and experiment are in apparent agreement concerning the energy difference between the peaks

Quantum Spin Dynamics of the Antiferromagnetic Linear Chain in Zero and Nonzero Magnetic Field

Spin-dynamical calculations on one-dimensional systems have relied heavily on classical (s = ∞) theories, despite abundant evidence that quantum effects can be extremely important at low temperatures. We present a new approach to the spin dynamics of the one-dimensional isotropic s=½ Heisenberg antiferromagnetic (HB AF) which does not involve the many-body techniques usually employed. It is based on analytic Bethe ansatz calculations of excitation energies and densities of states combined with finite-chain calculations of matrix elements. An important feature of our method is the use of rigorous selection rules and the introduction of new selection rules, which are valid for macroscopic systems in a magnetic field. We show that in zero field the dynamical two-spin correlation function Sμμ(q,ω) at T = 0 is governed by a two-parameter continuum of spin-wave-type excitations. In nonzero field, the longitudinal component Szz(q,ω) and the transverse components Sxx(q,ω) ≡ Syy(q,ω) behave quite differently because they are dominated by different continua of excitations. The former is characterized by a lowest excitation branch with a zero-frequency mode moving from the zone boundary (q = π) towards the zone center (q = 0) as the field increases, whereas the latter is characterized by a lowest branch with a zero frequency mode moving from q = 0 to π with increasing field. The first part of our work features an approximate analytic expression for Sμμ(q,ω) at zero temperature and in zero field. Although our expression is not rigorous, exact sum rules are violated only by a small amount, and good agreement exists with the few known exact results. Our studies are extended to nonzero temperatures by placing major reliance on exact finite-chain calculations. Our work was stimulated by recent neutron scattering experiments and is oriented towards experimental comparisons. Our result for the s=½ integrated intensity is in much better agreement with neutron scattering data on CuCl2·2N(C5D5) (CPC) than the corresponding semiclassical result. Moreover, the spectral-weight distribution in Sμμ(q,ω) shows increasing asymmetry as q→π, a quantum effect, again in agreement with more recent neutron scattering data. The second part of our work deals with the effects of an applied magnetic field. We extend the analytic work of Ishimura and Shiba to obtain expressions for the energies and densities of states of the various excitation continua. It is shown that these continua are expected to give rise to multiple structures in the scattering intensity. Our results appear to be in quantitative agreement with preliminary results of a neutron study in CPC in a field of 70 kOe, revealing anomalous scattering intensity peaks. Our results repeatedly demonstrate the inadequacy of classical spin-wave theory for this problem. They call for additional experimental studies on quasi-one-dimensional antiferromagnets to examine other unusual and interesting phenomena predicted by our approach

Magnetic Field Effects on the Spin Dynamics of the Linear Spin-1/2 Heisenberg Antiferromagnet

We present a new approach to the low temperature dynamics of a quantum Heisenberg antiferromagnetic chain, which employs a combination of techniques: exact finite chain calculations; exact Bethe Ansatz calculations; and exact sum rules and selection rules. A striking property of the selection rules is that the contribution of several classes of states to the dynamics in non-zero field for finite systems is shown to vanish in the thermodynamic limit. Many novel quantum field-dependent effects appear such as soft modes, and multiple peak structure in the structure factor, which should be experimentally observable

Quantum Spin Chains

Serious scientific interest in one-dimensional (1-D) physics arose in the early 1960’s. This interest was stimulated by exact as well as accurate numerical solutions to a variety of quantum spin chain problems [1]. The potential relevance of such solutions to real experimental systems was first demonstrated by Griffiths [2] in conjunction with workers at the Kamerlingh Onnes Laboratorium, Leiden. Theory and experiment were shown to be in excellent agreement for a naturally quasi-1-D Heisenberg spin 1/2 antiferromagnet, copper tetrammine sulphate [Cu(NH3)4SO4·H2O]. Further stimulus to the new field of quasi-1-D magnetism was provided by an annotated collection of reprinted papers on a variety of 1-D model systems, including lattice gases, dynamical disordered crystal lattices, many-fermion gases (electron gases) as well as magnets. The collection appeared in book form, and remains today an important introduction to 1-D theory [3]

Vincristine Side Effects with Concomitant Fluconazole Use during Induction Chemotherapy in Pediatric Acute Lymphoblastic Leukemia

As a mainstay of treatment for acute lymphoblastic leukemia (ALL), vincristine’s side effect profile is well known. Parallel administration of the antifungal fluconazole has been shown to interfere with the metabolism of vincristine, potentially resulting in increased side effects. We conducted a retrospective chart review to determine whether concomitant administration of vincristine and fluconazole during pediatric ALL therapy impacted side effects of vincristine, namely, hyponatremia and peripheral neuropathy. We also evaluated whether the incidence of opportunistic fungal infections was impacted by fluconazole prophylaxis. Medical charts of all pediatric ALL patients treated with induction chemotherapy at Children’s Hospital and Medical Center in Omaha, NE from 2013-2021 were retrospectively reviewed. We found no correlation between fluconazole use and increased incidence of peripheral neuropathy or hyponatremia. Additionally, the rate of fungal infections was not impacted by fluconazole prophylaxis. Empiric fungal prophylaxis with fluconazole during pediatric ALL induction, although safe, may not be necessary.https://digitalcommons.unmc.edu/chri_forum/1039/thumbnail.jp

Pediatric Acute Lymphoblastic Leukemia Patients and Potential Risk for Vincristine Side Effects with Concomitant Fluconazole

Background: Pediatric Acute Lymphoblastic Leukemia (ALL) patients undergoing intensive treatment are considered at high risk for opportunistic infections. To prevent invasive fungal infection, some patients receive antifungal prophylaxis such as fluconazole. As a consequence, an increase in vincristine toxicity has been associated with the co-administration of antifungal prophylaxis. We analyzed whether the use of fluconazole prophylaxis impacts vincristine’s side effects during induction therapy. Method: We conducted a retrospective chart review of all pediatric (age 0-18 years) patients diagnosed with ALL at Children’s Hospital and Medical Center in Omaha, Nebraska from July 2013-May 2021. Patients were divided into two groups based on whether or not they received fluconazole. Incidence of fungal infection, rate and grade of peripheral neuropathy, and prescription for gabapentin (treatment for peripheral neuropathy) were collected for both groups. Results: We had 157 ALL patients, of which 72 patients received fluconazole, and 85 patients did not receive fluconazole. There was no significant difference between fluconazole use and increased incidence of peripheral neuropathy (p value= 0.28) or incidence of hyponatremia (p value =Conclusion: We did not find a statistically significant difference that the use of concomitant fluconazole with vincristine increased the risk of peripheral neuropathy or hyponatremia.https://digitalcommons.unmc.edu/surp2021/1037/thumbnail.jp

Smoking decreases the response of human lung macrophages to double-stranded RNA by reducing TLR3 expression

Abstract Background Cigarette smoking is associated with increased frequency and duration of viral respiratory infections, but the underlying mechanisms are incompletely defined. We investigated whether smoking reduces expression by human lung macrophages (Mø) of receptors for viral nucleic acids and, if so, the effect on CXCL10 production. Methods We collected alveolar macrophages (AMø) by bronchoalveolar lavage of radiographically-normal lungs of subjects undergoing bronchoscopies for solitary nodules (n = 16) and of volunteers who were current or former smokers (n = 7) or never-smokers (n = 13). We measured expression of mRNA transcripts for viral nucleic acid receptors by real-time PCR in those AMø and in the human Mø cell line THP-1 following phorbol myristate acetate/vitamin D3 differentiation and exposure to cigarette smoke extract, and determined TLR3 protein expression using flow cytometry and immunohistochemistry. We also used flow cytometry to examine TLR3 expression in total lung Mø from subjects undergoing clinically-indicated lung resections (n = 25). Of these, seven had normal FEV1 and FEV1/FVC ratio (three former smokers, four current smokers); the remaining 18 subjects (14 former smokers; four current smokers) had COPD of GOLD stages I-IV. We measured AMø production of CXCL10 in response to stimulation with the dsRNA analogue poly(I:C) using Luminex assay. Results Relative to AMø of never-smokers, AMø of smokers demonstrated reduced protein expression of TLR3 and decreased mRNA for TLR3 but not TLR7, TLR8, TLR9, RIG-I, MDA-5 or PKR. Identical changes in TLR3 gene expression were induced in differentiated THP-1 cells exposed to cigarette smoke-extract in vitro for 4 hours. Among total lung Mø, the percentage of TLR3-positive cells correlated inversely with active smoking but not with COPD diagnosis, FEV1% predicted, sex, age or pack-years. Compared to AMø of never-smokers, poly(I:C)-stimulated production of CXCL10 was significantly reduced in AMø of smokers. Conclusions Active smoking, independent of COPD stage or smoking duration, reduces both the percent of human lung Mø expressing TLR3, and dsRNA-induced CXCL10 production, without altering other endosomal or cytoplasmic receptors for microbial nucleic acids. This effect provides one possible mechanism for increased frequency and duration of viral lower respiratory tract infections in smokers. Trial registration ClinicalTrials.gov NCT00281190 , NCT00281203 and NCT00281229 .http://deepblue.lib.umich.edu/bitstream/2027.42/134585/1/12931_2012_Article_1336.pd

Critical perspectives on ‘consumer involvement’ in health research: epistemological dissonance and the know-do gap

Researchers in the area of health and social care (both in Australia and internationally) are encouraged to involve consumers throughout the research process, often on ethical, political and methodological grounds, or simply as ‘good practice’. This paper presents findings from a qualitative study in the UK of researchers’ experiences and views of consumer involvement in health research. Two main themes are presented in the paper. Firstly, we explore the ‘know-do gap’ which relates to the tensions between researchers’ perceptions of the potential benefits of, and their actual practices in relation to, consumer involvement. Secondly, we focus on one of the reasons for this ‘know-do gap’, namely epistemological dissonance. Findings are linked to issues around consumerism in research, lay/professional knowledges, the (re)production of professional and consumer identities and the maintenance of boundaries between consumers and researchers

Determinants of Depressive Symptoms at 1 Year Following ICU Discharge in Survivors of $ 7 Days of Mechanical Ventilation : Results From the RECOVER Program, a Secondary Analysis of a Prospective Multicenter Cohort Study

Abstract : Background: Moderate to severe depressive symptoms occur in up to one-third of patients at 1 year following ICU discharge, negatively affecting patient outcomes. This study evaluated patient and caregiver factors associated with the development of these symptoms. Methods: This study used the Rehabilitation and Recovery in Patients after Critical Illness and Their Family Caregivers (RECOVER) Program (Phase 1) cohort of 391 patients from 10 medical/surgical university-affiliated ICUs across Canada. We determined the association between patient depressive symptoms (captured by using the Beck Depression Inventory II [BDI-II]), patient characteristics (age, sex, socioeconomic status, Charlson score, and ICU length of stay [LOS]), functional independence measure (FIM) motor subscale score, and caregiver characteristics (Caregiver Assistance Scale and Center for Epidemiologic Studies-Depression Scale) by using linear mixed models at time points 3, 6, and 12 months. Results: BDI-II data were available for 246 patients. Median age at ICU admission was 56 years (interquartile range, 45-65 years), 143 (58%) were male, and median ICU LOS was 19 days (interquartile range, 13-32 days). During the 12-month follow-up, 67 of 246 (27.2%) patients had a BDI-II score ≥ 20, indicating moderate to severe depressive symptoms. Mixed models showed worse depressive symptoms in patients with lower FIM motor subscale scores (1.1 BDI-II points per 10 FIM points), lower income status (by 3.7 BDI-II points; P = .007), and incomplete secondary education (by 3.8 BDI-II points; P = .009); a curvilinear relation with age (P = .001) was also reported, with highest BDI-II at ages 45 to 50 years. No associations were found between patient BDI-II and comorbidities (P = .92), sex (P = .25), ICU LOS (P = .51), or caregiver variables (Caregiver Assistance Scale [P = .28] and Center for Epidemiologic Studies Depression Scale [P = .74]). Conclusions: Increased functional dependence, lower income, and lower education are associated with increased severity of post-ICU depressive symptoms, whereas age has a curvilinear relation with symptom severity. Knowledge of risk factors may inform surveillance and targeted mental health follow-up. Early mobilization and rehabilitation aiming to improve function may serve to modify mood disorders