Reconciling scaling of the optical conductivity of cuprate superconductors with Planckian resistivity and specific heat

Materials tuned to a quantum critical point display universal scaling properties as a function of temperature T and frequency ω. A long-standing puzzle regarding cuprate superconductors has been the observed power-law dependence of optical conductivity with an exponent smaller than one, in contrast to T-linear dependence of the resistivity and ω-linear dependence of the optical scattering rate. Here, we present and analyze resistivity and optical conductivity of La_2-xSr_xCuO₄ with x = 0.24. We demonstrate ℏω/k_BT scaling of the optical data over a wide range of frequency and temperature, T-linear resistivity, and optical effective mass proportional to [Formula: see text] corroborating previous specific heat experiments. We show that a T, ω-linear scaling Ansatz for the inelastic scattering rate leads to a unified theoretical description of the experimental data, including the power-law of the optical conductivity. This theoretical framework provides new opportunities for describing the unique properties of quantum critical matter.

Thermodynamic signatures of quantum criticality in cuprate superconductors

The three central phenomena of cuprate (copper oxide) superconductors are linked by a common doping level p*-at which the enigmatic pseudogap phase ends and the resistivity exhibits an anomalous linear dependence on temperature, and around which the superconducting phase forms a dome-shaped area in the phase diagram¹. However, the fundamental nature of p* remains unclear, in particular regarding whether it marks a true quantum phase transition. Here we measure the specific heat C of the cuprates Eu-LSCO and Nd-LSCO at low temperature in magnetic fields large enough to suppress superconductivity, over a wide doping range² that includes p*. As a function of doping, we find that C_el/T is strongly peaked at p* (where C_el is the electronic contribution to C) and exhibits a log(1/T) dependence as temperature T tends to zero. These are the classic thermodynamic signatures of a quantum critical point^3-5, as observed in heavy-fermion⁶ and iron-based⁷ superconductors at the point where their antiferromagnetic phase comes to an end. We conclude that the pseudogap phase of cuprates ends at a quantum critical point, the associated fluctuations of which are probably involved in d-wave pairing and the anomalous scattering of charge carriers.

Unusual Interplay between Superconductivity and Field-Induced Charge Order in YBa_{2}Cu_{3}O_{y}

We present a detailed study of the temperature (T) and magnetic field (H) dependence of the electronic density of states (DOS) at the Fermi level, as deduced from specific heat and Knight shift measurements in underdoped YBa_{2}Cu_{3}O_{y}. We find that the DOS becomes field independent above a characteristic field H_{DOS}, and that the H_{DOS}(T) line displays an unusual inflection near the onset of the long-range 3D charge-density wave order. The unusual S shape of H_{DOS}(T) is suggestive of two mutually exclusive orders that eventually establish a form of cooperation in order to coexist at low T. On theoretical grounds, such a collaboration could result from the stabilization of a pair-density wave state, which calls for further investigation in this region of the phase diagram.

Effectiveness of antibacterial prophylaxis during induction chemotherapy in children with acute lymphoblastic leukemia

BACKGROUND

Pediatric patients receiving induction chemotherapy for newly diagnosed acute lymphoblastic leukemia (ALL) are at high risk of developing life-threatening infections. We investigated whether uniform antibacterial guidelines, including mandatory antibacterial prophylaxis in afebrile patients during induction, decreases the incidence of microbiologically documented bacteremia.

METHODS

Between 2012 and 2015, 230 patients with newly diagnosed ALL (aged 1-21) were enrolled on Dana-Farber Cancer Institute ALL Consortium Protocol 11-001 (DFCI 11-001). Induction therapy, regardless of risk group, included vincristine, prednisone, doxorubicin, methotrexate, and PEG-asparaginase. Afebrile patients received fluoroquinolone prophylaxis at the initiation of induction and those presenting with fever received broad-spectrum antibiotics; antibiotics were continued until blood count recovery. Rates of documented bacteremias and fungal infections on DFCI 11-001 were compared to those on the predecessor protocol (DFCI 05-001), which included the same induction phase without antibiotic prophylaxis guidelines.

RESULTS

Sixty-six (28.7%) patients received fluoroquinolone prophylaxis, the remaining patients received broad-spectrum antibiotics. Twenty-four (36.4%) patients on prophylaxis developed fever and seven (10.6%) developed bacteremia. The overall rate of infection during induction on DFCI 11-001 was lower than on DFCl 05-001 (14.3% vs. 26.3%, P < 0.0001) due to a decreased rate of bacteremia (10.9% vs. 24.4%, P < 0.0001). The rate of fungal infections (4.8% vs. 3.6%) and induction death (0.9% vs. 2%) was not significantly different.

CONCLUSION

For children with newly diagnosed ALL, uniform antibiotic administration until blood count recovery, including fluoroquinolone prophylaxis for afebrile patients, reduced the incidence of bacteremia during the induction phase. Larger, randomized studies should be performed to confirm these findings.

Molecular analysis and genotype-phenotype correlation of Diamond-Blackfan anemia

Diamond-Blackfan anemia (DBA) features hypoplastic anemia and congenital malformations, largely caused by mutations in various ribosomal proteins. The aim of this study was to characterize the spectrum of genetic lesions causing DBA and identify genotypes that correlate with phenotypes of clinical significance. Seventy-four patients with DBA from across Canada were included. Nucleotide-level mutations or large deletions were identified in 10 ribosomal genes in 45 cases. The RPS19 mutation group was associated with higher requirement for chronic treatment for anemia than other DBA groups. Patients with RPS19 mutations, however, were more likely to maintain long-term corticosteroid response without requirement for further chronic transfusions. Conversely, patients with RPL11 mutations were less likely to need chronic treatment. Birth defects, including cardiac, skeletal, hand, cleft lip or palate and genitourinary malformations, also varied among the various genetic groups. Patients with RPS19 mutations had the fewest number of defects, while patients with RPL5 had the greatest number of birth defects. This is the first study to show differences between DBA genetic groups with regards to treatment. Previously unreported differences in the rate and types of birth defects were also identified. These data allow better patient counseling, a more personalized monitoring plan, and may also suggest differential functions of DBA genes on ribosome and extra-ribosomal functions.

How to interpret high levels of distress when using the Distress Thermometer in the long-term follow-up clinic? A study with Acute Lymphoblastic Leukemia survivors

OBJECTIVES

Recent guidelines recommend to assess emotional distress in pediatric oncology during treatment and in after care. One tool used to do this is the distress thermometer (DT), a simple tool which has almost exclusively been studied in its screening abilities. Given its increased used as a measure of distress per se, it is necessary to document its concurrent validity. The goal of this study was to identify clinical domains (eg, depression, anxiety) and individual symptoms associated with pediatric cancer survivors' rating on the DT.

PARTICIPANTS

To do so we used data collected from 84 young (≤18 years old), and 120 older (>18 years old) survivors who were treated for pediatric leukemia.

METHODS

Participants responded to self-report questionnaires as part of a research visit.

RESULTS

Results from stepwise regressions show that in the younger group, high scores on the thermometer were associated with higher negative affectivity only. In adults, high scores were associated with higher anxiety, higher negative affectivity, and lower positive affectivity. When exploring associations with individual items, we found that the main emotional tone reflected by the thermometer score was anxiety.

CONCLUSIONS

Interpreting ratings on the thermometer should probably focus on anxiety in childhood cancer survivors. This widely used tool also does not measure the same domains in young versus older survivors, so that age groups should be considered separately in future work.

DESCRIPTION D’UNE COHORTE RÉTROSPECTIVE DE PATIENTS PÉDIATRIQUES ATTEINTS DE THROMBOPÉNIE IMMUNE AIGUË

BACKGROUND: La thrombopénie immune (TPI) aiguë est une condition fréquente dont la prise en charge demeure controversée. Les lig-nes directrices suggèrent de traiter les enfants présentant des saignements modérés ou sévères avec des corticostéroïdes ou des immu-noglobulines (IVIg).

OBJECTIVES: L’objectif principal est de décrire des patients pédiatriques atteints de TPI aiguë. Les objectifs secondaires sont de décrire les effets indé-sirables et les répercussions sur les soins associés au traitement par IVIg.

DESIGN/METHODS: Il s’agit d’une étude de cohorte rétrospective par révision de dossiers. Les patients inclus sont âgés entre 1 et 17 ans, atteints de TPI aiguë et ont été traités dans notre établissement du 2004-01-01 au 2014-06-01. La classification des saignements est définie selon celle utili-sée dans les lignes directrices.

RESULTS: Les 88 patients ont un âge moyen de 6.9 ans. À l’arrivée, 87/88 (98,9%) patients présentaient des saignements : 5/87 (5,7%) sévères, 24/87 (27,6%) modérés, 58/87 (66,7%) mineurs ou légers et aucun saigne-ment menaçant la vie (comme une hémorragie intracrânienne). Les pla-quettes initiales moyennes étaient de 11,0×109/L et 63/88 (71,6%) patients avaient un taux ≤10×109/L. Initialement, 77/88 (87.5%) patients ont été traités : 62/77 (80,5%) avec des IVIg, 8/77 (10,4%) avec des corticosté-roïdes et 3/77 (3,9%) avec les deux traitements combinés. 40/88 (45%) patients ont reçu plus d'un traitement, dont 23/40 (57,5%) en moins de 48 heures. 5/77 (6,4%) patients ont reçu une transfusion de plaquettes. Une réponse au traitement initial a été obtenue chez 62/77 (80,5 %) patients. Une TPI chronique s’est développée chez 15/88 (17,0%) patients. Parmi les patients ayant reçu des IVIg au moins une fois, 42/74 (56,8%) ont présenté des effets indésirables associés à ce produit sanguin dont 10/42 (23,8%) des nausées, 28/42 (66,7%) des vomissements et 31/42 (73,8%) des céphalées. Ceux-ci sont associés à une imagerie cérébrale chez 5/88 (5,7%) patients (toutes normales).

CONCLUSION: Notre étude démontre le caractère mineur des saigne-ments à la présentation initiale du patient avec TPI. Ceci appuie les lig-nes directrices qui limitent le nombre de patients traités. Malgré cette présentation par des saignements surtout mineurs ou légers, un grand nombre de patients est traité dans notre milieu et plus de 80% le sont avec des IVIg. Cette pratique semble associée à des effets indésirables et investigations supplémentaires, ce qui devrait être pris en compte lors du choix du traitement initial.

Infectious Episodes in Paediatric Patients with Moderate-To-Severe Chronic Benign Neutropenia and Normal Bone Marrow Evaluation

BACKGROUND: Chronic benign neutropenia, often referred as primary autoimmune neutropenia, is the most frequent cause of chronic neutrope-nia in children. Despite being a common and long known entity, evidence supporting its benign infectious course is scarce. More data would help guiding parents and clinicians in regard to patient evolution.

OBJECTIVES: The aim of this study was to describe infectious episodes in children with moderate to severe autoimmune neutropenia supported by a normal bone marrow study. Secondary objectives were to determine the mean duration of the neutropenia and whether the severity of the neutro-penia was correlated to the development of severe infections.

DESIGN/METHODS: We retrospectively reviewed medical records of patients with chronic neutropenia followed by a pediatric hematologist at our tertiary pediatric center, between November 1995 and December 2013. We only included patients with chronic benign neutropenia supported by a normal bone marrow. We excluded patients with immune deficiencies, genetic syndromes and metabolic diseases. Simple and multiple logistic regression were used to determine the association between the presence of severe infections and the absolute neutrophil count (ANC). We classified the severity of infection according to the medical literature.

RESULTS: 84 medical records were retrospectively reviewed. 21 patients were excluded from the study based on exclusion criteria. We were able to collect complete data for 37 patients. The median age at diagnosis and at resolution was respectively 9 months (2mo-13yr) and 37 months (9mo-16y). The median duration of the neutropenia was 17 months (3mo-5y). During the neutropenic period, more than 112 mild infections were observed. 11 patients (29.7%) developed 13 moderate infections. 7 patients (18.9%) underwent 8 severe infections but no bacteremia was reported. ANC was not significantly different between patients who exhibited severe infections and those who did not (mean ANC=663±322×106/L vs 601±326×106/L; p=0.67). Recurrent infections occurred in 9 patients (24.3%).

CONCLUSION: To our knowledge, our study is the largest on benign chronic neutropenia in children with normal bone evaluation. Severe infections have infrequently been reported in the literature for children with chronic benign neutropenia. Yet, almost 20% of our cohort exhibited at least one severe infection, although no bacteremia occurred. Interestingly, no association was found between the severity of the neu-tropenia and the presence of severe infection. We believe that these findings will help guiding the evaluation and management in this commonly occurring affection.

Single nucleotide polymorphism in IL1B is associated with infection risk in paediatric acute myeloid leukaemia

We evaluated single nucleotide polymorphisms (SNPs) associated with infection risk in children with newly diagnosed acute myeloid leukaemia (AML). We conducted a multicentre, prospective cohort study that included children aged ≤18 years with de novo AML. DNA was isolated from blood lymphocytes or buccal swabs, and candidate gene SNP analysis was conducted. Primary outcome was the occurrence of microbiologically documented sterile site infection during chemotherapy. Secondary outcomes were Gram-positive and -negative infections, viridans group streptococcal infection and proven/probable invasive fungal infection. Interpretation was guided by consistency in risk alleles and microbiologic agent with previous literature. Over the study period 254 children and adolescents with AML were enrolled. Overall, 190 (74.8%) had at least one sterile site microbiologically documented infection. Among the 172 with inferred European ancestry and DNA available, nine significant associations were observed; two were consistent with previous literature. Allele A at IL1B (rs16944) was associated with decreased microbiologically documented infection, and allele G at IL10 (rs1800896) was associated with increased risk of Gram-positive infection. We identified SNPs associated with infection risk in paediatric AML. Genotype may provide insight into mechanisms of infection risk that could be used for supportive-care novel treatments.

Genetic analysis of inherited bone marrow failure syndromes from one prospective, comprehensive and population-based cohort and identification of novel mutations

INTRODUCTION

Inherited bone marrow failure syndromes (IBMFSs) often have substantial phenotypic overlap, thus genotyping is often critical for establishing a diagnosis.

OBJECTIVES AND METHODS

To determine the genetic characteristics and mutation profiles of IBMFSs, a comprehensive population-based study that prospectively enrols all typical and atypical cases without bias is required. The Canadian Inherited Marrow Failure Study is such a study, and was used to extract clinical and genetic information for patients enrolled up to May 2010.

RESULTS

Among the 259 primary patients with IBMFS enrolled in the study, the most prevalent categories were Diamond-Blackfan anaemia (44 patients), Fanconi anaemia (39) and Shwachman-Diamond syndrome (35). The estimated incidence of the primary IBMFSs was 64.5 per 10(6) births, with Fanconi anaemia having the highest incidence (11.4 cases per 10(6) births). A large number of patients (70) had haematological and non-haematological features that did not fulfil the diagnostic criteria of any specific IBMFS category. Disease-causing mutations were identified in 53.5% of the 142 patients tested, and in 16 different genes. Ten novel mutations in SBDS, RPL5, FANCA, FANCG, MPL and G6PT were identified. The most common mutations were nonsense (31 alleles) and splice site (28). Genetic heterogeneity of most IBMFSs was evident; however, the most commonly mutated gene was SBDS, followed by FANCA and RPS19.

CONCLUSION

From this the largest published comprehensive cohort of IBMFSs, it can be concluded that recent advances have led to successful genotyping of about half of the patients. Establishing a genetic diagnosis is still challenging and there is a critical need to develop novel diagnostic tools.

[Urethro-vesical suspension performed by the vaginal approach]

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