Quasi-1D dynamics and nematic phases in the 2D Emery model

We consider the Emery model of a Cu-O plane of the high temperature superconductors. We show that in a strong-coupling limit, with strong Coulomb repulsions between electrons on nearest-neighbor O sites, the electron-dynamics is strictly one dimensional, and consequently a number of asymptotically exact results can be obtained concerning the electronic structure. In particular, we show that a nematic phase, which spontaneously breaks the point- group symmetry of the square lattice, is stable at low enough temperatures and strong enough coupling.Comment: 8 pages, 5 eps figures; revised manuscript with more detailed discussions; two new figures and three edited figuresedited figures; 14 references; new appendix with a detailed proof of the one-dimensional dynamics of the system in the strong coupling limi

Outcome following surgery for colorectal cancer: analysis by hospital after adjustment for case-mix and deprivation

Outcome, adjusted for case-mix and deprivation, in 3200 patients undergoing resection for colorectal cancer in 11 hospitals in Central Scotland between 1991 and 1994 was studied. There were significant differences among individual hospitals in the proportion of elderly (P<0.001) and deprived (P<0.0001) patients, the mode (P=0.007) and stage (P<0.0001) at presentation, and the proportion of patients who underwent apparently curative resection (P<0.001). There were no significant differences in postoperative mortality. Cancer-specific survival at 5 years following apparently curative resection varied from 59 to 76%; cancer-specific survival at 2 years following palliative resection varied from 22 to 44%. The corresponding hazard ratios, adjusted for the above prognostic factors, for patients undergoing apparently curative resection varied among hospitals from 0.58 to 1.32; and the ratios for palliative resection varied from 0.73 to 1.26. This study demonstrates that, after adjustment for variations in case-mix and deprivation, significant differences in outcome among hospitals following resection for colorectal cancer persist

Determinants of pre-vaccination antibody responses to SARS-CoV-2: a population-based longitudinal study (COVIDENCE UK)

BACKGROUND: Prospective population-based studies investigating multiple determinants of pre-vaccination antibody responses to SARS-CoV-2 are lacking. METHODS: We did a prospective population-based study in SARS-CoV-2 vaccine-naive UK adults recruited between May 1 and November 2, 2020, without a positive swab test result for SARS-CoV-2 prior to enrolment. Information on 88 potential sociodemographic, behavioural, nutritional, clinical and pharmacological risk factors was obtained through online questionnaires, and combined IgG/IgA/IgM responses to SARS-CoV-2 spike glycoprotein were determined in dried blood spots obtained between November 6, 2020, and April 18, 2021. We used logistic and linear regression to estimate adjusted odds ratios (aORs) and adjusted geometric mean ratios (aGMRs) for potential determinants of SARS-CoV-2 seropositivity (all participants) and antibody titres (seropositive participants only), respectively. RESULTS: Of 11,130 participants, 1696 (15.2%) were seropositive. Factors independently associated with  higher risk of SARS-CoV-2 seropositivity included frontline health/care occupation (aOR 1.86, 95% CI 1.48–2.33), international travel (1.20, 1.07–1.35), number of visits to shops and other indoor public places (≥ 5 vs. 0/week: 1.29, 1.06–1.57, P-trend = 0.01), body mass index (BMI) ≥ 25 vs. < 25 kg/m(2) (1.24, 1.11–1.39), South Asian vs. White ethnicity (1.65, 1.10–2.49) and alcohol consumption ≥15 vs. 0 units/week (1.23, 1.04–1.46). Light physical exercise associated with  lower risk (0.80, 0.70–0.93, for ≥ 10 vs. 0–4 h/week). Among seropositive participants, higher titres of anti-Spike antibodies associated with factors including BMI ≥ 30 vs. < 25 kg/m(2) (aGMR 1.10, 1.02–1.19), South Asian vs. White ethnicity (1.22, 1.04–1.44), frontline health/care occupation (1.24, 95% CI 1.11–1.39), international travel (1.11, 1.05–1.16) and number of visits to shops and other indoor public places (≥ 5 vs. 0/week: 1.12, 1.02–1.23, P-trend = 0.01); these associations were not substantially attenuated by adjustment for COVID-19 disease severity. CONCLUSIONS: Higher alcohol consumption and lower light physical exercise represent new modifiable risk factors for SARS-CoV-2 infection. Recognised associations between South Asian ethnic origin and obesity and higher risk of SARS-CoV-2 seropositivity were independent of other sociodemographic, behavioural, nutritional, clinical, and pharmacological factors investigated. Among seropositive participants, higher titres of anti-Spike antibodies in people of South Asian ancestry and in obese people were not explained by greater COVID-19 disease severity in these groups. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12916-022-02286-4

An angle-resolved photoemission spectral function analysis of the electron doped cuprate Nd_1.85Ce_0.15CuO_4

Using methods made possible by recent advances in photoemission technology, we perform an indepth line-shape analysis of the angle-resolved photoemission spectra of the electron doped (n-type) cuprate superconductor Nd_1.85Ce_0.15CuO_4. Unlike for the p-type materials, we only observe weak mass renormalizations near 50-70 meV. This may be indicative of smaller electron-phonon coupling or due to the masking effects of other interactions that make the electron-phonon coupling harder to detect. This latter scenario may suggest limitations of the spectral function analysis in extracting electronic self-energies when some of the interactions are highly momentum dependent.Comment: 8 pages, 5 figure

An ARPES view on the high-Tc problem: phonons vs spin-fluctuations

We review the search for a mediator of high-Tc superconductivity focusing on ARPES experiment. In case of HTSC cuprates, we summarize and discuss a consistent view of electronic interactions that provides natural explanation of both the origin of the pseudogap state and the mechanism for high temperature superconductivity. Within this scenario, the spin-fluctuations play a decisive role in formation of the fermionic excitation spectrum in the normal state and are sufficient to explain the high transition temperatures to the superconducting state while the pseudogap phenomenon is a consequence of a Peierls-type intrinsic instability of electronic system to formation of an incommensurate density wave. On the other hand, a similar analysis being applied to the iron pnictides reveals especially strong electron-phonon coupling that suggests important role of phonons for high-Tc superconductivity in pnictides.Comment: A summary of the ARPES part of the Research Unit FOR538, http://for538.wmi.badw.d

A novel selection of optimal statistical features in the DWPT domain for discrimination of ictal and seizure-free electroencephalography signals

Properly determining the discriminative features which characterize the inherent behaviors of electroencephalography (EEG) signals remains a great challenge for epileptic seizure detection. In this present study, a novel feature selection scheme based on the discrete wavelet packet decomposition and cuckoo search algorithm (CSA) was proposed. The normal as well as epileptic EEG recordings were frst decomposed into various frequency bands by means of wavelet packet decomposition, and subsequently, statistical features at all developed nodes in the wavelet packet decomposition tree were derived. Instead of using the complete set of the extracted features to construct a wavelet neural networks-based classifer, an optimal feature subset that maximizes the predictive competence of the classifer was selected by using the CSA. Experimental results on the publicly available benchmarks demonstrated that the proposed feature subset selection scheme achieved promising recognition accuracies of 98.43–100%, and the results were statistically signifcant using z-test with p value <0.0001

Magnetic neutron scattering in hole doped cuprate superconductors

A review is presented of the static and dynamic magnetic properties of hole-doped cuprate superconductors measured with neutron scattering. A wide variety of experiments are described with emphasis on the monolayer La_{2-x}(Sr,Ba)_{x}CuO_{4} and bilayer YBa_{2}Cu_{3}O_{6+x} cuprates. At zero hole doping, both classes of materials are antiferromagnetic insulators with large superexchange constants of J > 100 meV. For increasing hole doping, the cuprates become superconducting at a critical hole concentration of x_{c}=0.055. The development of new instrumentation at neutron beam sources coupled with the improvement in materials has lead to a better understanding of these materials and the underlying spin dynamics over a broad range of hole dopings. We will describe how the spin dispersion changes across the insulating to superconducting boundary as well as the static magnetic properties which are directly coupled with the superconductivity. Experiments directly probing the competing magnetic and superconducting order parameters involving magnetic fields, impurity doping, and structural order will be examined. Correlations between superconductivity and magnetism will also be discussed.Comment: 14 pages, 18 figures. To be published in Journal of the Physical Society of Japa

Universal relation between magnetic resonance and superconducting gap in unconventional superconductors

Unconventional superconductors such as the high-transition temperature cuprates, heavy-fermion systems and iron arsenide-based compounds exhibit antiferromagnetic fluctuations that are dominated by a resonance, a collective spin-one excitation mode in the superconducting state. Here we demonstrate the existence of a universal linear relation, $Er \propto 2\Delta$, between the magnetic resonance energy (Er) and the superconducting pairing gap ($\Delta$), spanning two orders of magnitude in energy. This relation is valid for materials that range from being close to the Mott-insulating limit to being on the border of itinerant magnetism. Since the common excitonic picture of the resonance has not led to such universality, our observation suggests a much deeper connection between antiferromagnetic fluctuations and unconventional superconductivity.Comment: 19 pages, 5 figures, 2 table

Risk factors for developing COVID-19: a population-based longitudinal study (COVIDENCE UK)

Background: Risk factors for severe COVID-19 include older age, male sex, obesity, black or Asian ethnicity and underlying medical conditions. Whether these factors also influence susceptibility to developing COVID-19 is uncertain. Methods: We undertook a prospective, population-based cohort study (COVIDENCE UK) from 1 May 2020 to 5 February 2021. Baseline information on potential risk factors was captured by an online questionnaire. Monthly follow-up questionnaires captured incident COVID-19. We used logistic regression models to estimate multivariable-adjusted ORs (aORs) for associations between potential risk factors and odds of COVID-19. Results: We recorded 446 incident cases of COVID-19 in 15 227 participants (2.9%). Increased odds of developing COVID-19 were independently associated with Asian/Asian British versus white ethnicity (aOR 2.28, 95% CI 1.33 to 3.91), household overcrowding (aOR per additional 0.5 people/bedroom 1.26, 1.11 to 1.43), any versus no visits to/from other households in previous week (aOR 1.31, 1.06 to 1.62), number of visits to indoor public places (aOR per extra visit per week 1.05, 1.02 to 1.09), frontline occupation excluding health/social care versus no frontline occupation (aOR 1.49, 1.12 to 1.98) and raised body mass index (BMI) (aOR 1.50 (1.19 to 1.89) for BMI 25.0–30.0 kg/m2 and 1.39 (1.06 to 1.84) for BMI >30.0 kg/m2 versus BMI <25.0 kg/m2). Atopic disease was independently associated with decreased odds (aOR 0.75, 0.59 to 0.97). No independent associations were seen for age, sex, other medical conditions, diet or micronutrient supplement use. Conclusions: After rigorous adjustment for factors influencing exposure to SARS-CoV-2, Asian/Asian British ethnicity and raised BMI were associated with increased odds of developing COVID-19, while atopic disease was associated with decreased odds. Trial registration number: ClinicalTrials.gov Registry (NCT04330599)