Transition to the Haldane phase driven by electron-electron correlations

One of the most famous quantum systems with topological properties, the spin [Formula: see text] antiferromagnetic Heisenberg chain, is well-known to display exotic [Formula: see text] edge states. However, this spin model has not been analyzed from the more general perspective of strongly correlated systems varying the electron-electron interaction strength. Here, we report the investigation of the emergence of the Haldane edge in a system of interacting electrons - the two-orbital Hubbard model-with increasing repulsion strength U and Hund interaction JH. We show that interactions not only form the magnetic moments but also form a topologically nontrivial fermionic many-body ground-state with zero-energy edge states. Specifically, upon increasing the strength of the Hubbard repulsion and Hund exchange, we identify a sharp transition point separating topologically trivial and nontrivial ground-states. Surprisingly, such a behaviour appears already at rather small values of the interaction, in a regime where the magnetic moments are barely developed.

Pediatric Atypical Melanocytic Proliferations: Single-Site Retrospective Cohort Assessment of Treatment and Long-Term Follow-Up

Atypical and malignant cutaneous tumors are understudied in the pediatric population, with limited data on long-term follow-up. This study examines pediatric (0-18 years) atypical melanocytic proliferations over a twenty-year period (January 2002-December2022) using the EPIC SlicerDicer at our institution. Over a twenty-year period, there were 55 cases of pediatric melanoma (53 patients). The median follow-up time was 8 years, 11 months. A proportion of 96% were treated with wide local excision (WLE), and 47% had a sentinel lymph node biopsy (SLNB) (35% positive rate). There were 101 atypical Spitz tumor cases (85% atypical Spitz tumors, 15% Spitz melanoma), with a median follow-up duration of 9 years. A proportion of 77% were treated with WLE (with one patient dying of metastatic disease). There were 10 cases of atypical melanocytic proliferations not otherwise specified, including 5 pigmented epithelioid melanocytomas (PEM), 4 deep-penetrating nevi, and 1 atypical cellular blue nevus. This study adds to the growing body of knowledge on pediatric atypical cutaneous melanocytic proliferations, aligning with many described characteristics such as disease location and overall survival rates, with distinct exceptions (higher melanoma positive SLNB rate, lower atypical Spitz tumor WLE rate, and a case of fatal metastatic atypical Spitz tumor).

Do Walk Step Reminders Improve Physical Activity in Persons Living With HIV in New York City?-Results From a Randomized Clinical Trial

ABSTRACT

Supervised physical activity can increase functional capacity in persons with HIV (PWH); however, aerobic interventions have shown little improvement in overall physical activity in PWH. In response, we sought to assess the effect of wearing a fitness tracker (FitBit) paired with walk step reminders delivered through an mHealth application to improve physical activity and decreasing body mass index among PWH in New York City. There was no significant difference in the frequency of walk steps between participants in the control group and intervention group from baseline to 6-month follow-up. These findings show that walk step reminders alone were inadequate for sustained improvement of physical activity. This study highlights the need to develop and test the comparative efficacy of physical activity interventions that are tailored to the unique needs and capabilities of PWH. Future interventions should incorporate fitness tracking with tailored interventions focused on the promotion of physical activity.Clinical Trials.Gov Registration number: NCT03205982.

Onychocytic Matricoma Presenting as Longitudinal Melanonychia in a Skin of Color Patient

Introduction

Onychocytic matricoma (OCM) is a benign acanthoma of the nail matrix that presents with longitudinal melanonychia and nail thickening. Only 18 previously reported cases of OCM are in the literature since it was first described in 2012.

Case Presentation

The purpose of this case report was to report a unique presentation of OCM in the toenail of a Black patient as well as to review the clinical presentation, histologic features, and management of this rare entity. Previously described cases presented on the fingernails and were predominantly in white males.

Conclusion

OCM is a benign entity that may mimic a nail unit melanoma or squamous cell carcinoma especially when pachyonychia is present. Despite some clinical clues to suggest a diagnosis of OCM, a nail matrix biopsy is often required to rule out malignancy.

Theoretically Guided Iterative Design of the Sense2Quit App for Tobacco Cessation in Persons Living with HIV

The use of mobile health (mHealth technology) can be an effective intervention when considering chronic illnesses. Qualitative research methods were used to identify specific content and features for a mobile app for smoking cessation amongst people living with HIV (PWH). We conducted five focus group sessions followed by two Design Sessions with PWH who were or are currently chronic cigarette smokers. The first five groups focused on the perceived barriers and facilitators to smoking cessation amongst PWH. The two Design Sessions leveraged the findings from the focus group sessions and were used to determine the optimal features and user interface of a mobile app to support smoking cessation amongst PWH. Thematic analysis was conducted using the Health Belief Model and Fogg's Functional Triad. Seven themes emerged from our focus group sessions: history of smoking, triggers, consequences of quitting smoking, motivation to quit, messages to help quit, quitting strategies, and mental health-related challenges. Functional details of the app were identified during the Design Sessions and used to build a functional prototype.

A Systematic Review of Self-Management Interventions Conducted Across Global Settings for Depressive Symptoms in Persons with HIV

Depressive symptoms can affect health outcomes in people living with HIV (PLWH) including adherence to treatment and disease prognosis. Self-management interventions targeting depressive symptoms have been effective in preventing these negative sequelae of depressive symptoms. The processes of self-management include learning skills related to living with the illness needs, accessing resources to manage the illness, and coping with the illness. A systematic literature review was conducted to appraise and synthesize the current evidence of self-management interventions targeting depressive symptoms in PLWH. Following the PRISMA guidelines, an electronic search of 4 databases was conducted. Original studies written in English that used a randomized controlled trial design to test the effect of self-management intervention on depressive symptoms were included. Studies were selected that were published on/before April 19, 2022, thus yielding 13 relevant articles. Risk of bias was assessed using the NIH Quality Assessment Tool for Controlled Intervention Studies and narrative synthesis was used to synthesize the results. 40 to 755 participants were included in the studies, with each using various measures to assess depressive symptoms pre-and post-intervention, and timepoints for assessing depressive symptoms post-intervention varied. While 12 studies showed a significant reduction in depressive symptoms post-intervention, only 4 studies that used individual coaching or technology showed lower depressive symptoms in intervention groups in comparison to the control groups. This review can be used to inform scale-up and dissemination of these interventions to improve depressive symptoms in PLWH.

A Smoking Cessation Mobile App for Persons Living With HIV: Preliminary Efficacy and Feasibility Study

BACKGROUND

The prevalence of smoking in the United States general population has gradually declined to the lowest rate ever recorded; however, this has not been true for persons with HIV.

OBJECTIVE

We conducted a pilot test to assess the feasibility and efficacy of the Lumme Quit Smoking mobile app and smartwatch combination with sensing capabilities to improve smoking cessation in persons with HIV.

METHODS

A total of 40 participants were enrolled in the study and randomly assigned 1:1 to the control arm, which received an 8-week supply of nicotine replacement therapy, a 30-minute smoking cessation counseling session, and weekly check-in calls with study staff, or to the intervention arm, which additionally received the Lumme Quit Smoking app and smartwatch.

RESULTS

Of the 40 participants enrolled, 37 completed the follow-up study assessments and 16 used the app every day during the 56-day period. During the 6-month recruitment and enrollment period, 122 people were screened for eligibility, with 67.2% (82/122) deemed ineligible. Smoking criteria and incompatible tech were the major reasons for ineligibility. There was no difference in the proportion of 7-day point prevalence abstinence by study arm and no significant decrease in exhaled carbon monoxide for the intervention and control arms separately. However, the average exhaled carbon monoxide decreased over time when analyzing both arms together (P=.02).

CONCLUSIONS

Results suggest excellent feasibility and acceptability of using a smoking sensor app among this smoking population. The knowledge gained from this research will enable the scientific community, clinicians, and community stakeholders to improve tobacco cessation outcomes for persons with HIV.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04808609; https://clinicaltrials.gov/ct2/show/NCT04808609.

POS1156 INFECTIONS AND OTHER ADVERSE EFFECTS WITH BIOLOGICAL THERAPIES OVER THE PAST 10 YEARS

Background:

Biological therapies have marked a difference in the treatment of many autoimmune conditions. As all treatments, they have their side effects although little evidence of long-term effects has been reported.

Objectives:

Analyze retrospectively the appearance of infections that required hospitalization and other side effects in patients treated with biological therapies over the past 10 years.

Methods:

Biological drugs dispensed in our center to non-cancer patients from 2008 to 2018 were reviewed. Health records were collected from our database and all statistical analyzes were performed with the SPSS program.

Results:

24 different biological drugs applied to 34 medical conditions; 847 treatments were dispensed over a total of 555 patients. The median age was 44 years with a mean duration of 3.6 years of treatment. The most commonly used drug were adalimumab (n = 280, 33%), infliximab (n = 119, 12%), etanercept (n = 97.13%), rituximab (n = 63, 7%), vedolizumab (n = 47, 5.5%) and omalizumab (n = 43.5%). The rest of the drugs were administered <30 times each (ustekinumab, golimumab, certolizumab, tocilizumab, secukinumab and abatacept), representing <4% of the total sample.

The underlying conditions included Crohn’s Disease (n = 262, 31%), rheumatoid arthritis (n = 133, 16%), ulcerative colitis (n = 118, 14%), spondyloarthropathies (n = 86, 10%), psoriatic arthritis (n = 56, 7%), psoriasis (n = 49, 6%), asthma (n = 34, 4%), nephropathies (n = 19, 2%) and vasculitis (n = 13, 1.5%). The rest were pathologies with <10 cases.

During treatment, infection requiring hospitalization occurred in 10.2% (n = 86). The most frequent focus of infection was respiratory (n = 23, 27%), abdominal (n = 19, 22%), soft tissue-bone (n = 17 cases, 20%), urinary (n = 7, 8%) and tuberculosis (n = 4, 5%). No case of hepatitis reactivation was observed. At the time of hospital admission, 46% of patients were only under biological therapy, 21% had another non-corticosteroid immunosuppressant, 17% were associated with corticosteroid, and 15% had triple therapy (corticosteroids, another immunosuppressant and the biological drug). The drugs associated with more infections were: abatacept 20%, rituximab 16% and adalimumab 13%.

During the study period, 14 deaths (1.7%) were observed; being the cause cancer-related (n=5), infection (n=5), the disease itself for which was receiving biological treatment (n=2), and endocrine metabolic causes (n=2).

At the end of the review, 48% of the treatments were still in use, while 52% had stopped for various reasons: 20% ineffectiveness, 12% side effects, 12% maintained complete remission. The remaining low percentage was due to death, pregnancy, or study entry.

The side effects that led to a change in treatment was: non-immune hematological disorders in 4.1% (14% of tocilizumab, 7% of rituximab and 6% of vedolizumab), immune disorders in 3.8% (6% of secukinumab, 5% of tocilizumab and 4.5% of certolizumab), nervous system involvement in 2.4% (11.5% of golimumab,10% of abatacept, 5% of tocilizumab), debut or worsening of heart failure in 1.4% (9, 5% of tocilizumab, 2.5% of etanercept and 1.4% of adalimumab) and cancer-related in 0.7% (2% of infliximab, 1.7% of etanercept).

Conclusion:

In these 10 years of follow-up and and evaluating 847 treatments, there were 10% hospitalizations due to infections (n = 86) causing death in 5 patients. In light of these results, and pending an exhaustive statistical analysis, we did not find high frequencies of serious side effects in our series. Very little long-term evidence exists on the safety of these drugs.

References:

[1]Singh JA, Wells GA, Christensen R, et al. Adverse effects of biologics: a network meta-analysis and Cochrane overview. Cochrane Database Syst Rev. 2011;2011(2):CD008794. Published 2011 Feb 16.

Disclosure of Interests:

None declared.

Block-spiral magnetism: An exotic type of frustrated order

Competing interactions in quantum materials induce exotic states of matter such as frustrated magnets, an extensive field of research from both the theoretical and experimental perspectives. Here, we show that competing energy scales present in the low-dimensional orbital-selective Mott phase (OSMP) induce an exotic magnetic order, never reported before. Earlier neutron-scattering experiments on iron-based 123 ladder materials, where OSMP is relevant, already confirmed our previous theoretical prediction of block magnetism (magnetic order of the form [Formula: see text]). Now we argue that another phase can be stabilized in multiorbital Hubbard models, the block-spiral state. In this state, the magnetic islands form a spiral propagating through the chain but with the blocks maintaining their identity, namely rigidly rotating. The block-spiral state is stabilized without any apparent frustration, the common avenue to generate spiral arrangements in multiferroics. By examining the behavior of the electronic degrees of freedom, parity-breaking quasiparticles are revealed. Finally, a simple phenomenological model that accurately captures the macroscopic spin spiral arrangement is also introduced, and fingerprints for the neutron-scattering experimental detection are provided.

International Nosocomial Infection Control Consortium (INICC) report, data summary of 45 countries for 2012-2017: Device-associated module

BACKGROUND

We report the results of International Nosocomial Infection Control Consortium (INICC) surveillance study from January 2012 to December 2017 in 523 intensive care units (ICUs) in 45 countries from Latin America, Europe, Eastern Mediterranean, Southeast Asia, and Western Pacific.

METHODS

During the 6-year study period, prospective data from 532,483 ICU patients hospitalized in 242 hospitals, for an aggregate of 2,197,304 patient days, were collected through the INICC Surveillance Online System (ISOS). The Centers for Disease Control and Prevention-National Healthcare Safety Network (CDC-NHSN) definitions for device-associated health care-associated infection (DA-HAI) were applied.

RESULTS

Although device use in INICC ICUs was similar to that reported from CDC-NHSN ICUs, DA-HAI rates were higher in the INICC ICUs: in the medical-surgical ICUs, the pooled central line-associated bloodstream infection rate was higher (5.05 vs 0.8 per 1,000 central line-days); the ventilator-associated pneumonia rate was also higher (14.1 vs 0.9 per 1,000 ventilator-days,), as well as the rate of catheter-associated urinary tract infection (5.1 vs 1.7 per 1,000 catheter-days). From blood cultures samples, frequencies of resistance, such as of Pseudomonas aeruginosa to piperacillin-tazobactam (33.0% vs 18.3%), were also higher.

CONCLUSIONS

Despite a significant trend toward the reduction in INICC ICUs, DA-HAI rates are still much higher compared with CDC-NHSN's ICUs representing the developed world. It is INICC's main goal to provide basic and cost-effective resources, through the INICC Surveillance Online System to tackle the burden of DA-HAIs effectively.

Morphological, biochemical and functional studies to evaluate bovine oocyte vitrification

The aim of the present study was to evaluate the effect of vitrification on morphological, biochemical and functional parameters of matured bovine oocytes at different recovery times. To this end, matured bovine oocytes were vitrified using the Cryotech® kit (a minimum-volume system) and then incubated in maturation medium for different post-warming durations (0 h, 3 h or 21 h). Morphology, viability and biochemical parameters were assessed at each time point mentioned above and the recovery of the metaphase plate was analyzed at 2 h, 3 h and 4 h post-warming. The vitrification-warming process did not affect the viability or morphology of oocytes at any time point. However, the recovery of the metaphase plate occurred mostly between 3 and 4 h rather than at 2 h after warming (P < 0.05). Both control and vitrified-warmed oocytes showed changes in cytosolic oxidative activity, quantification of active mitochondria, reactive oxygen species (ROS) levels and redox status at the different time points studied (P < 0.05). However, differences between control and vitrified-warmed oocytes were found only in the quantification of active mitochondria and ROS production (P < 0.05). Finally, in vitro fertilization and embryo culture were carried out as functional studies to establish whether vitrification-warming affected oocyte competence, and a significant decrease was found both in the cleavage rate and embryo development (P < 0.05). We concluded that major improvements in oocyte vitrification, at list with Cryotech® kit, are still needed to avoid variations in oocyte metabolism which could contribute to the reduction in the developmental competence of bovine oocytes.

Threat-of-shock decreases emotional interference on affective stroop performance in healthy controls and anxiety patients

Patients with anxiety disorders suffer from impaired concentration, potentially as a result of stronger emotional interference on attention. Studies using behavioural measures provide conflicting support for this hypothesis. Elevated state anxiety may be necessary to reliably document differences in emotional interference in patients versus healthy controls. The present study examines the effect of experimentally induced state anxiety (threat-of-shock) on attention interference by emotional stimuli. Anxiety patients (n = 36) and healthy controls (n = 32) completed a modified affective Stroop task during periods of safety and threat-of-shock. Results indicated that in both patients and controls, threat decreased negative, but not positive or neutral, emotional interference on attention (both p < .001). This finding supports a threat-related narrowing of attention whereby a certain level of anxiety decreases task-irrelevant processing.

Novel Magnetic Block States in Low-Dimensional Iron-Based Superconductors

Inelastic neutron scattering recently confirmed the theoretical prediction of a ↑↑↓↓-magnetic state along the legs of quasi-one-dimensional iron-based ladders in the orbital-selective Mott phase (OSMP). We show here that electron doping of the OSMP induces a whole class of novel block states with a variety of periodicities beyond the previously reported π/2 pattern. We discuss the magnetic phase diagram of the OSMP regime that could be tested by neutrons once appropriate quasi-1D quantum materials with the appropriate dopings are identified.

Probing the Electrostatic and Steric Requirements for Substrate Binding in Human Platelet-Type 12-Lipoxygenase

Human platelet ALOX12 (hALOX12 or h12-LOX) has been implicated in a variety of human diseases. The present study investigates the active site of hALOX12 to more thoroughly understand how it positions the substrate and achieves nearly perfect regio- and stereospecificities (i.e., 100 ± 5% of the 12(S)-hydroperoxide product), utilizing site-directed mutagenesis. Specifically, we have determined that Arg402 is not as important in substrate binding as previously seen for hALOX15 but that His596 may play a role in anchoring the carboxy terminal of the arachidonic acid during catalysis. In addition, Phe414 creates a π-stacking interaction with a double bond of arachidonic acid (Δ¹¹), and Ala417/Val418 define the bottom of the cavity. However, the influence of Ala417/Val418 on the profile is markedly less for hALOX12 than that seen in hALOX15. Mutating these two residues to larger amino acids (Ala417Ile/Val418Met) only increased the generation of 15-HpETE by 24 ± 2%, but conversely, smaller residues at these positions converted hALOX15 to almost 100% hALOX12 reactivity [Gan et al. (1996) J. Biol. Chem. 271, 25412-25418]. However, we were able to increase 15-HpETE to 46 ± 3% by restricting the width of the active site with the Ala417Ile/Val418Met/Ser594Thr mutation, indicating both depth and width of the active site are important. Finally, residue Leu407 is shown to play a critical role in positioning the substrate correctly, as seen by the increase of 15-HpETE to 21 ± 1% for the single Leu407Gly mutant. These results outline critical differences between the active site requirements of hALOX12 relative to hALOX15 and explain both their product specificity and inhibitory differences.

Computing Resonant Inelastic X-Ray Scattering Spectra Using The Density Matrix Renormalization Group Method

We present a method for computing the resonant inelastic x-ray scattering (RIXS) spectra in one-dimensional systems using the density matrix renormalization group (DMRG) method. By using DMRG to address this problem, we shift the computational bottleneck from the memory requirements associated with exact diagonalization (ED) calculations to the computational time associated with the DMRG algorithm. This approach is then used to obtain RIXS spectra on cluster sizes well beyond state-of-the-art ED techniques. Using this new procedure, we compute the low-energy magnetic excitations observed in Cu L-edge RIXS for the challenging corner shared CuO4 chains, both for large multi-orbital clusters and downfolded t-J chains. We are able to directly compare results obtained from both models defined in clusters with identical momentum resolution. In the strong coupling limit, we find that the downfolded t-J model captures the main features of the magnetic excitations probed by RIXS only after a uniform scaling of the spectra is made.

Distinct responses to predictable and unpredictable threat in anxiety pathologies: effect of panic attack

Background

Delineating specific clinical phenotypes of anxiety disorders is a crucial step toward better classification and understanding of these conditions. The present study sought to identify differential aversive responses to predictable and unpredictable threat of shock in healthy comparisons and in non-medicated anxiety patients with and without a history of panic attacks (PAs).

Method

143 adults (72 healthy controls; 71 patients with generalized anxiety disorder (GAD) or/and social anxiety disorder (SAD), 24 with and 47 without PAs) were exposed to three conditions: 1) predictable shocks signaled by a cue, 2) unpredictable shocks, and 3) no shock. Startle magnitude was used to assess aversive responses.

Results

Across disorders, a PA history was specifically associated with hypersensitivity to unpredictable threat. By disorder, SAD was associated with hypersensitivity to predictable threat, whereas GAD was associated with exaggerated baseline startle.

Conclusions

These results identified three physiological patterns. The first is hypersensitivity to unpredictable threat in individuals with PAs. The second is hypersensitivity to predictable threat, which characterizes SAD. The third is enhanced baseline startle in GAD, which may reflect propensity for self-generated anxious thoughts in the absence of imminent danger. These results inform current thinking by linking specific clinical features to particular physiology profiles.

Clinical anxiety promotes excessive response inhibition

BACKGROUND

Laboratory tasks to delineate anxiety disorder features are used to refine classification and inform our understanding of etiological mechanisms. The present study examines laboratory measures of response inhibition, specifically the inhibition of a pre-potent motor response, in clinical anxiety. Data on associations between anxiety and response inhibition remain inconsistent, perhaps because of dissociable effects of clinical anxiety and experimentally manipulated state anxiety. Few studies directly assess the independent and interacting effects of these two anxiety types (state v. disorder) on response inhibition. The current study accomplished this goal, by manipulating state anxiety in healthy and clinically anxious individuals while they complete a response inhibition task.

METHOD

The study employs the threat-of-shock paradigm, one of the best-established manipulations for robustly increasing state anxiety. Participants included 82 adults (41 healthy; 41 patients with an anxiety disorder). A go/nogo task with highly frequent go trials was administered during alternating periods of safety and shock threat. Signal detection theory was used to quantify response bias and signal-detection sensitivity.

RESULTS

There were independent effects of anxiety and clinical anxiety on response inhibition. In both groups, heightened anxiety facilitated response inhibition, leading to reduced nogo commission errors. Compared with the healthy group, clinical anxiety was associated with excessive response inhibition and increased go omission errors in both the safe and threat conditions.

CONCLUSIONS

Response inhibition and its impact on go omission errors appear to be a promising behavioral marker of clinical anxiety. These results have implications for a dimensional view of clinical anxiety.

Spectral functions with the density matrix renormalization group: Krylov-space approach for correction vectors

Frequency-dependent correlations, such as the spectral function and the dynamical structure factor, help illustrate condensed matter experiments. Within the density matrix renormalization group (DMRG) framework, an accurate method for calculating spectral functions directly in frequency is the correction-vector method. The correction vector can be computed by solving a linear equation or by minimizing a functional. This paper proposes an alternative to calculate the correction vector: to use the Krylov-space approach. This paper then studies the accuracy and performance of the Krylov-space approach, when applied to the Heisenberg, the t-J, and the Hubbard models. The cases studied indicate that the Krylov-space approach can be more accurate and efficient than the conjugate gradient, and that the error of the former integrates best when a Krylov-space decomposition is also used for ground state DMRG.

Anxiety-mediated facilitation of behavioral inhibition: Threat processing and defensive reactivity during a go/no-go task

Anxiety can be broken down into multiple facets including behavioral components, such as defensive reactivity, and cognitive components, such as distracting anxious thoughts. In a previous study, we showed that anticipation of unpredictable shocks facilitated response inhibition to infrequent no-go trials during a go/no-go task. The present study extends this work to examine the distinct contribution of defensive reactivity, measures with fear-potentiated startle, and anxious thought, assessed with thought probes, on go and no-go performance. Consistent with our prior findings, shock anticipation facilitated response inhibition (i.e., reduced errors of commission) on the no-go trials. Regression analyses showed that (a) no-go accuracy was positively associated with fear-potentiated startle and negatively associated with threat-related/task-unrelated thoughts and (b) go accuracy correlated negatively with fear-potentiated startle. Thus, while the present findings confirm the influence of anxiety on response inhibition, they also show that such influence reflects the balance between the positive effect of defensive reactivity and the negative effect of distracting anxious thoughts. (PsycINFO Database Record

Spin Andreev-like reflection in metal-Mott insulator heterostructures

Using the time-dependent density-matrix renormalization group (tDMRG), we study the time evolution of electron wave packets in one-dimensional (1D) metal-superconductor heterostructures. The results show Andreev reflection at the interface, as expected. By combining these results with the well-known single-spin-species electron-hole transformation in the Hubbard model, we predict an analogous spin Andreev reflection in metal-Mott insulator heterostructures. This effect is numerically confirmed using 1D tDMRG, but it is expected to also be present in higher dimensions, as well as in more general Hamiltonians. We present an intuitive picture of the spin reflection, analogous to that of Andreev reflection at metal-superconductor interfaces. This allows us to discuss a novel antiferromagnetic proximity effect. Possible experimental realizations are discussed.

[Natural history of an optic disc macroaneurysm]

CASE REPORT

A 75-year old man with reduced vision in his left eye (0.05) presented with hypertensive retinopathy, retinal haemorrhages and cotton wool spots in the papillomacular bundle, as well as macular oedema. Fluorescein angiography showed a saccular hyperfluorescent lesion corresponding to arterial macroaneurysm on the optic disc, with the optical coherence tomography demonstrating macular oedema. At 2 months follow-up, vision had improved to 0.7 with spontaneous closure of the macroaneurysm and resolution of the macular oedema.

DISCUSSION

Arterial macroaneurysms on the optic disc are unusual and are difficult to diagnose clinically. There is no safe and effective treatment, and our case, as the few single cases reported, showed that they can spontaneously close and enable visual function to recover.

Elastic energy of the discocyte-stomatocyte transformation

The aim of this study is to calculate the membrane elastic energy for the different shapes observed in the discocyte-stomatocyte sequence. This analysis can provide a better quantitative understanding of the hypothesis put forward over the last decades to explain how red blood cells produce and maintain their typical shape. For this purpose, we use geometrical models based on parametric equations. The energy model considered for the elastic properties of RBC membrane includes the local and nonlocal resistance effects of the bilayer to bending. In particular, the results confirm the discocyte as the lowest energy value configuration among the sets of different red blood cell deformations considered in the sequence.