Effective lattice actions for correlated electrons

We present an exact, unconstrained representation of the electron operators in terms of operators of opposite statistics. We propose a path--integral representation for the $t$-$J$ model and introduce a parameter controlling the semiclassical behaviour. We extend the functional approach to the Hubbard model and show that the mean--field theory is equivalent to considering, at Hamiltonian level, the Falikov--Kimball model. Connections with a bond-charge model are also discussed.Comment: 12 pages, REVTeX 3.0, no figure

Circuits for local and global signal integration in primary visual cortex

Journal ArticleContrast-dependent changes in spatial summation and contextual modulation of primary visual cortex (V1) neuron responses to stimulation of their receptive field reveal long-distance integration of visual signals within V1, well beyond the classical receptive field (cRF) of single neurons. To identify the cortical circuits mediating these long-distance computations, we have used a combination of anatomical and physiological recording methods to determine the spatial scale and retinotopic logic of intra-areal V1 horizontal connections and inter-areal feedback connections to V1. We have then compared the spatial scales of these connectional systems to the spatial dimensions of the cRF, spatial summation field (SF), and modulatory surround field of macaque V1 neurons. We find that monosynaptic horizontal connections within area V1 are of an appropriate spatial scale to mediate interactions within the SF of V1 neurons and to underlie contrast-dependent changes in SF size. Contrary to common beliefs, these connections cannot fully account for the dimensions of the surround field. The spatial scale of feedback circuits from extrastriate cortex to V1 is, instead, commensurate with the full spatial range of center-surround interactions. Thus these connections could represent an anatomical substrate for contextual modulation and global-to-local integration of visual signals. Feedback projections connect corresponding and equal-sized regions of the visual field in striate and extrastriate cortices and cover anisotropic parts of visual space, unlike V1 horizontal connections that are isotropic in the macaque. V1 isotropic connectivity demonstrates that anisotropic horizontal connections are not necessary to generate orientation selectivity. Anisotropic feedback connections may play a role in contour completion

Segregation and overlap of callosal and association neurons in frontal and parietal cortices of primates: a spectral and coherency analysis.

Journal ArticleThe spatial relations between selected classes of association and callosal neurons were studied in the frontal and parietal lobes of the macaque monkey using retrogradely transported fluorescent dyes. Fast blue and nuclear yellow were injected in the left frontal (areas 4 and 6) and right posterior parietal (area 5) cortices, respectively. These injections led to the retrograde labeling, in the right frontal cortex, of callosal neurons projecting homotopically and association neurons projecting to ipsilateral area 5; in the left superior parietal lobule, of callosal neurons projecting to contralateral area 5 and association neurons projecting to the ipsilateral frontal lobe. In both frontal and parietal cortices, callosal and association neurons were located in layers III and V-VI; a few neurons were also found in layer II. The contribution of layers V-VI to the callosum was significantly higher in areas 4 and 6 than in area 5. Only a small number of neurons (less than 1%) were double labeled. Spectral analyses were used to characterize the spatial periodicities of the distributions of callosal and association neurons. In areas 4, 6, and 5, both association and callosal spectra were dominated by a strong elevation in the range of low spatial frequencies, corresponding to periodicities in cell density with a peak-to-peak distance of about 8 mm. This indicated an arrangement of these corticocortical cells in the form of bands. The latter displayed various shapes and orientations and were composed of more discrete assemblies of cell clusters of about 400-1000 microns width. Their presence was revealed in the power spectra by a small elevation in the range of high spatial frequencies. The coherency analysis assessed the degree of linear relationships for each spatial frequency, and therefore the degree of similarity, between callosal and association cell distributions, together with their phase relations. Little coherency was found in areas 4 and 6 between bands of callosal and association neurons, which suggests that the 2 cell populations are differently and independently distributed in the tangential domain, with no simple phase relations. The overall mean coherency was higher in area 5 than in the frontal cortex: callosal and association bands were more similar in shape, with more extensive zones of overlap. These data indicate that callosal and association neurons share common principles of spatial organization despite the great regional variability of their interrelations in the tangential cortical domain

Some exact results for the multicomponent t-J model

We present a generalization of the Sutherland's multicomponent model. Our extension includes both the ferromagnetic and the antiferromagnetic t-J model for any value of the exchange coupling J and the hopping parameter t. We prove rigorously that for one dimensional chains the ground-state of the generalized model is non-degenerate. As a consequence, the ordering of energy levels of the antiferromagnetic t-J model is determined. Our result rigorously proves and extends the analysis carried out by Sutherland in establishing the phase diagram of the model as a function of the number of components.Comment: 11 pages, RevTeX 3.0, no figure

Patient characteristics associated with the acceptability of teleconsultation: a retrospective study of osteoporotic patients post-COVID-19

Background: Due to the COVID-19 pandemic, teleconsultations (TCs) have become common practice for many chronic conditions, including osteoporosis. While satisfaction with TCs among patients increases in times of emergency, we have little knowledge of whether the acceptability of TCs persists once in-person visits return to being a feasible and safe option. In this study, we assess the acceptability of TCs across five dimensions for osteoporosis care among patients who started or continued with TCs after the COVID-19 pandemic had waned. We then explore the patient characteristics associated with these perceptions. Methods: Between January and April 2022, 80 osteoporotic patients treated at the Humanitas Hospital in Milan, Italy, were recruited to answer an online questionnaire about the acceptability of TCs for their care. The acceptability of TCs was measured using a modified version of the Service User Technology Acceptability Questionnaire (SUTAQ), which identifies five domains of acceptability: perceived benefits, satisfaction, substitution, privacy and discomfort, and care personnel concerns. Multivariable ordinary least squares (OLS) linear regression analysis was performed to assess which patient characteristics in terms of demographics, socio-economic conditions, digital skills, social support, clinical characteristics and pattern of TC use were correlated with the five domains of acceptability measured through the SUTAQ. Results: The degree of acceptability of TCs was overall good across the 80 respondents and the five domains. Some heterogeneity in perceptions emerged with respect to TCs substituting for in-person visits, negatively impacting continuity of care and reducing the length of consultations. For the most part, acceptability was not affected by patient characteristics with a few exceptions related to treatment time and familiarity with the TC service modality (i.e., length of osteoporosis treatment and number of TCs experienced by the patient). Conclusions: TCs appear to be an acceptable option for osteoporosis care in the aftermath of the COVID-19 pandemic. This study suggests that other characteristics besides age, digital skills and social support, which are traditionally relevant to TC acceptability, should be taken into account in order to better target this care delivery modality

Dataset of Electoral Volatility in the European Parliament elections since 1979

This dataset provides data on electoral volatility and its internal components in the elections for the European Parliament (EP) in all European Union (EU) countries since 1979 or the date of their accession to the Union. It also provides data about electoral volatility for both the class bloc and the demarcation bloc. This dataset will be regularly updated so as to include the next rounds of the European Parliament elections. How to cite this dataset? Emanuele, V., Angelucci, D., Marino, B., Puleo, L., and Vegetti, F. (2019), Dataset of Electoral Volatility in the European Parliament elections since 1979, Rome: Italian Center for Electoral Studies, http://dx.doi.org/10.7802/1905

A participatory process to design an app to improve adherence to anti-osteoporotic therapies: A development and usability study

Objective: The aim of the study was to develop an app to improve patients’ adherence to therapy for osteoporosis and to test its usability. Methods: In Phase I, the app functions needed to improve medication adherence were identified through a focus group with six patients with osteoporosis and a joint interview with two bone specialists. The app prototype was then developed (Phase II) and refined after its feasibility testing (Phase III) for 13–25 days by eight patients. Finally, the app underwent usability testing (Phase IV) for 6 months by nine other patients. The mHealth App Usability Questionnaire (MAUQ) was used to collect the assessment of the app by the 17 patients. Results: The final version of the app provided information on osteoporosis, allowed patients to contact the bone specialist for an additional consultation, and generated a reminder for taking medications accompanied by feedback on adherence. The assessment of the app was positive but evaluations differed between the feasibility and usability testing, with the former displaying a significantly (p ≤.05) better assessment across all MAUQ items. Conclusions: In this study, we tested an app for improving adherence to medical therapies in patients with osteoporosis. The usability testing revealed a lower “patient-centered” performance of the app as compared to that observed during the feasibility phase. Future developments of the study include increasing the testing cohort and adding a technical support during the usability testing

Integrated Trigger and Data Acquisition system for the NA62 experiment at CERN

The main goal of the NA62 experiment is to measure the branching ratio of the K+decay, collecting O(100) events in two years of data taking. Efficient online selection of interesting events and loss-less readout at high rate will be key issues for such experiment. An integrated trigger and data acquisition system has been designed. Only the very first trigger stage will be implemented in hardware, in order to reduce the total rate for the software levels on PC farms. Readout uniformity among different subdetectors and scalability were taken into account in the architecture design

Iron-dependent trafficking of 5-lipoxygenase and impact on human macrophage activation

5-lipoxygenase (5-LOX) is a non-heme iron-containing dioxygenase expressed in immune cells that catalyzes the two initial steps in the biosynthesis of leukotrienes. It is well known that 5-LOX activation in innate immunity cells is related to different iron-associated proinflammatory disorders, including cancer, neurodegenerative diseases, and atherosclerosis. However, the molecular and cellular mechanism(s) underlying the interplay between iron and 5-LOX activation are largely unexplored. In this study, we investigated whether iron (in the form of Fe3+ and hemin) might modulate 5-LOX influencing its membrane binding, subcellular distribution, and functional activity. We proved by fluorescence resonance energy transfer approach that metal removal from the recombinant human 5-LOX, not only altered the catalytic activity of the enzyme, but also impaired its membrane-binding. To ascertain whether iron can modulate the subcellular distribution of 5-LOX in immune cells, we exposed THP-1 macrophages and human primary macrophages to exogenous iron. Cells exposed to increasing amounts of Fe3+ showed a redistribution (ranging from ~45 to 75%) of the cytosolic 5-LOX to the nuclear fraction. Accordingly, confocal microscopy revealed that acute exposure to extracellular Fe3+, as well as hemin, caused an overt increase in the nuclear fluorescence of 5-LOX, accompanied by a co-localization with the 5-LOX activating protein (FLAP) both in THP-1 macrophages and human macrophages. The functional relevance of iron overloading was demonstrated by a marked induction of the expression of interleukin-6 in iron-treated macrophages. Importantly, pre-treatment of cells with the iron-chelating agent deferoxamine completely abolished the hemin-dependent translocation of 5-LOX to the nuclear fraction, and significantly reverted its effect on interleukin-6 overexpression. These results suggest that exogenous iron modulates the biological activity of 5-LOX in macrophages by increasing its ability to bind to nuclear membranes, further supporting a role for iron in inflammation-based diseases where its homeostasis is altered and suggesting further evidence of risks related to iron overload