371 research outputs found
Mean field spin glasses treated with PDE techniques
Following an original idea of F. Guerra, in this notes we analyze the
Sherrington-Kirkpatrick model from different perspectives, all sharing the
underlying approach which consists in linking the resolution of the statistical
mechanics of the model (e.g. solving for the free energy) to well-known partial
differential equation (PDE) problems (in suitable spaces). The plan is then to
solve the related PDE using techniques involved in their native field and
lastly bringing back the solution in the proper statistical mechanics
framework. Within this strand, after a streamlined test-case on the Curie-Weiss
model to highlight the methods more than the physics behind, we solve the SK
both at the replica symmetric and at the 1-RSB level, obtaining the correct
expression for the free energy via an analogy to a Fourier equation and for the
self-consistencies with an analogy to a Burger equation, whose shock wave
develops exactly at critical noise level (triggering the phase transition). Our
approach, beyond acting as a new alternative method (with respect to the
standard routes) for tackling the complexity of spin glasses, links symmetries
in PDE theory with constraints in statistical mechanics and, as a novel result
from the theoretical physics perspective, we obtain a new class of polynomial
identities (namely of Aizenman-Contucci type but merged within the Guerra's
broken replica measures), whose interest lies in understanding, via the recent
Panchenko breakthroughs, how to force the overlap organization to the
ultrametric tree predicted by Parisi
Anergy in self-directed B lymphocytes from a statistical mechanics perspective
The ability of the adaptive immune system to discriminate between self and
non-self mainly stems from the ontogenic clonal-deletion of lymphocytes
expressing strong binding affinity with self-peptides. However, some
self-directed lymphocytes may evade selection and still be harmless due to a
mechanism called clonal anergy. As for B lymphocytes, two major explanations
for anergy developed over three decades: according to "Varela theory", it stems
from a proper orchestration of the whole B-repertoire, in such a way that
self-reactive clones, due to intensive interactions and feed-back from other
clones, display more inertia to mount a response. On the other hand, according
to the `two-signal model", which has prevailed nowadays, self-reacting cells
are not stimulated by helper lymphocytes and the absence of such signaling
yields anergy. The first result we present, achieved through disordered
statistical mechanics, shows that helper cells do not prompt the activation and
proliferation of a certain sub-group of B cells, which turn out to be just
those broadly interacting, hence it merges the two approaches as a whole (in
particular, Varela theory is then contained into the two-signal model). As a
second result, we outline a minimal topological architecture for the B-world,
where highly connected clones are self-directed as a natural consequence of an
ontogenetic learning; this provides a mathematical framework to Varela
perspective. As a consequence of these two achievements, clonal deletion and
clonal anergy can be seen as two inter-playing aspects of the same phenomenon
too
GDM-complicated pregnancies: focus on adipokines
Gestational diabetes mellitus (GDM) is a serious complication of pregnancy and is defined as a state of glucose intolerance that is first diagnosed and arises during gestation. Although the pathophysiology of GDM has not yet been thoroughly clarified, insulin resistance and pancreatic β-cell dysfunction are considered critical components of its etiopathogenesis. To sustain fetus growth and guarantee mother health, many significant changes in maternal metabolism are required in normal and high-risk pregnancy accompanied by potential complications. Adipokines, adipose tissue-derived hormones, are proteins with pleiotropic functions including a strong metabolic influence in physiological conditions and during pregnancy too. A growing number of studies suggest that various adipokines including adiponectin, leptin, visfatin, resistin and tumor necrosis factor α (TNF-α) are dysregulated in GDM and might have pathological significance and a prognostic value in this pregnancy disorder. In this review, we will focus on the current knowledge on the role that the aforementioned adipokines play in the development and progression of GDM.Gestational diabetes mellitus (GDM) is a serious complication of pregnancy and is defined as a state of glucose intolerance that is first diagnosed and arises during gestation. Although the pathophysiology of GDM has not yet been thoroughly clarified, insulin resistance and pancreatic β-cell dysfunction are considered critical components of its etiopathogenesis. To sustain fetus growth and guarantee mother health, many significant changes in maternal metabolism are required in normal and high-risk pregnancy accompanied by potential complications. Adipokines, adipose tissue-derived hormones, are proteins with pleiotropic functions including a strong metabolic influence in physiological conditions and during pregnancy too. A growing number of studies suggest that various adipokines including adiponectin, leptin, visfatin, resistin and tumor necrosis factor α (TNF-α) are dysregulated in GDM and might have pathological significance and a prognostic value in this pregnancy disorder. In this review, we will focus on the current knowledge on the role that the aforementioned adipokines play in the development and progression of GDM
SH3-Hunter: discovery of SH3 domain interaction sites in proteins
SH3-Hunter (http://cbm.bio.uniroma2.it/SH3-Hunter/) is a web server for the recognition of putative SH3 domain interaction sites on protein sequences. Given an input query consisting of one or more protein sequences, the server identifies peptides containing poly-proline binding motifs and associates them to a list of SH3 domains, in order to compose peptide–domain pairs. The server can accept a list of peptides and allows users to upload an input file in a proper format. An accurate selection of SH3 domains is available and users can also submit their own SH3 domain sequence
A Cross-Sectional Survey on Burnout Prevalence and Profile in the Sicilian Population of Ambulance Driver-Rescuers
Introduction: Burnout is present at a high rate in emergency medicine. The ambulance
driver-rescuers, who furnish first aid to the victims, are the non-medical part of the
Italian 118-service staff. There is a lack of research on burnout risk in Italian Emergency
Medical Services and, particularly, for this category of workers. The two Italian studies,
including a little group of ambulance driver-rescuers, reported inconsistent findings.
Hypothesis: This survey investigated for the first time the prevalence and exact profile of
burnout in a large sample of Italian driver-rescuers. As a secondary aim, the study described
how the items of the Italian version of the Maslach Burnout Inventory-Human Services
Survey (MBI-HSS) cluster in components in this sample.
Methods: This cross-sectional census survey was conducted from June 2015 through May
2016 and involved all the driver-rescuers operating in Sicily, the biggest and most southern
region of Italy. The subjects received a classification according to different profiles of burnout by using the Italian version of the MBI-HSS (burnout, engagement, disengagement,
over-extension, and work-inefficacy). In order to explore the existence of independent
factors, a Principal Component Analysis (PCA) was conducted on the survey to obtain
eigenvalues >one for each component in the data.
Results: The final sample comprised 2,361 responders (96.6% of the initial sample). Of them,
29.8% were in burnout (95% confidence interval [CI], 27.8% to 31.8%) and 1.7% presented a
severe form (95% CI, 1.1% to 2.3%); 30.0% were engaged in their work (95% CI, 21.0% to
34.8%), 24.7% of responders were disengaged (95% CI, 22.9% to 26.5%), 1.2% presented an
over-extension profile (95% CI, 0.8% to 1.7%), and 12.6% felt work-inefficacy (95% CI,
11.3% to 14.1%). The factors loaded into a five-factor solution at PCA, explaining 48.1%
of the variance and partially replicating the three-factor structure. The Emotional
Exhaustion (EE) component was confirmed. New dimensions from Personal
Accomplishment (PA) and Depersonalization (DP) sub-scales described empathy and disengagement with patients, respectively, and were responsible for the increased risk of burnout.
Conclusions: These results endorse the importance of screening and psychological interventions for this population of emergency workers, where burnout could manifest itself more
insidiously. It is also possible to speculate that sub-optimal empathy skills could be related to
the disengagement and work-inefficacy feelings registered
Role of endocannabinoids and TRPV1 channels in the bioelectric activity of hippocampal neurons
It has been reported that endocannabinoid system is an important player in the regulation of neuronal bioelectrical activity, relying on receptor-mediated mechanisms. Amongst these, Cannabinoid receptor type 1 (CB1r) and Transient Receptor Potential Vanilloid type 1 (TRPV1) are both modulated by endocannabinoids, involved in the transduction of stimuli in the pre-synaptic neuron and prompt downstream pathways in the post-synaptic neuron. To investigate the role of CB1r/TRPV1 interplay, we applied whole-cell patch clamp technique to visualize the eventual variations in terms of membrane current and action potentials induced by pharmacological manipulation in rat hippocampal neurons. We modulated the activity of the CB1r and TRPV1 exploiting anandamide (AEA), CB1r and TRPV1 agonist, capsaicin (CAP), a TRPV1 agonist and capsazepine (CPZ), a TRPV1 antagonist. Our data show that AEA influences steady membrane current with respect to controls. Furthermore, drug application significantly modifies action potentials amplitude, duration and frequency. In particular, the co-treatment of AEA and CPZ increases the amplitude of action potentials, reduces their duration and thus increases their frequency. These preliminary results support the involvement of TRPV1 in the cannabinoid modulation of the bioelectrical activity in rat hippocampal neurons. Indeed, the concurrent blockade of these channels and activation of CBr influences basic properties of neuronal function
Is postoperative hyponatremia a real threat for total hip and knee arthroplasty surgery?
Postoperative hyponatremia (POH) is thought to be a fearsome complication of orthopedic surgery. Primary aim of this cohort study was to evaluate the incidence of POH and its clinical relevance in elective surgery, outlining differences between total knee arthroplasty (TKA) and total hip arthroplasty, looking for the presence of any risk factor commonly related to POH. Four hundred two patients that underwent total hip arthroplasty and total knee arthroplasty performed between 2016 and 2017 were retrospectively examined. Serum electrolytes, hemoglobin, hematocrit, glucose, and creatinine were evaluated preoperatively and at day 0-I-II from surgery. Age, sex, body mass index, comorbidities, drugs, surgery data, transfusions, postoperative symptoms, and length of stay (LOS) were determined. All surgeries were performed by the same equipe. Patients had the same perioperative management, excluded those that took thiazides, already at risk of POH. Patients were divided in 2 groups: group A, patients with normal postoperative natremia (294 patients) and group B, patients who developed POH (108, 26.9%); 66.7% of these developed POH within 24 hours postoperatively. In group B mean postoperative natremia was 133.38 (127.78-134.85) mmol/L. Two patients (1.8%) developed moderate hyponatremia, no severe hyponatremia was documented. Type of surgery, operation time, LOS, and presence of postoperative symptoms did not show statistically significant differences within groups. At multivariate logistic analysis chronic use of thiazides was the only variable associated to a decreased risk of developing POH (OR = 0.39;P = .03). Hemoglobin postoperative values (OR = 1.22;P = .03), the need of postoperative transfusion (OR = 2.50;P = .02) and diabetes (OR = 2.70;P = .01) were associated to an increased risk of POH. Although 26.9% of our patients exhibited POH, the onset of this disorder had no implication on postoperative symptoms and on LOS. Diabetes and transfusion are factors most often associated to POH
Intermittent Claudication: The Importance of Non-Invasive Treatment in the Femoro-Popliteal Tract
The prevalence of intermittent claudication is around 4.5% in general population aged between 55 to 74 years [1]. Even if this condition has a profound and negative impact on patients' quality of life [2,3], because of a sense of limitation of mobility and the fear of the progression of the disease and limb loss, patient should be reassured on the relatively benign prognosis of the pathology in case of intermittent claudication. Leng et al. [4] reported a remission of symptoms in more than 60% of the patients examined after a period of 5 years. A progression of the disease in only 25%; deterioration is more likely to appear on the first year after diagnosis (7%-9%) compared with 2% to 3% per year thereafter [5] and can be related to poor adherence to treatments and exercise programs
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