The role of fluid pressure in induced vs. triggered seismicity. Insights from rock deformation experiments on carbonates

Fluid overpressure is one of the primary mechanisms for tectonic fault slip, because fluids lubricate the fault and fluid pressure reduces the effective normal stress that holds the fault in place. However, current models of earthquake nucleation, based on rate- and state- friction laws, imply that stable sliding is favoured by the increase of pore fluid pressure. Despite this controversy, currently, there are only a few studies on the role of fluid pressure under controlled, laboratory conditions. Here, we use laboratory experiments, to show that the rate- and state- friction parameters do change with increasing fluid pressure. We tested carbonate gouges from sub hydrostatic to near lithostatic fluid pressure conditions, and show that the friction rate parameter (a−b) evolves from velocity strengthening to velocity neutral behaviour. Furthermore, the critical slip distance, Dc, decreases from about 90 to 10μm. Our data suggest that fluid overpressure plays an important role in controlling the mode of fault slip. Since fault rheology and fault stability parameters change with fluid pressure, we suggest that a comprehensive characterization of these parameters is fundamental for better assessing the role of fluid pressure in natural and human induced earthquakes

Surgical treatment of a rare case of bilateral ptosis due to localized ocular amyloidosis

We describe a rare case of a 31-year old woman with bilateral ptosis due to localized amyloidosis. She referred a nine-year history of ptosis and surgical treatment with frontalis suspension three years previously. Following complete ophthalmological examination and evaluation of the ptosis we carried out tarsal and fornix biopsy, which revealed accumulation of a weakly eosinophilic amyloid positive substance. We performed surgical correction using the levator aponeurosis–Müller’s muscle complex re-adaptation technique and amyloid substance debulking in all the palpebral layers in the left eye. The material obtained was stained with hematoxylin–eosin, Congo Red, PAS and alpha-actin, which confirmed amyloid deposition. Successively, the right eye was operated in the same manner and entropion was managed by dissection and removal of amyloid from subconjunctival layers. Five years following surgery, the corrective procedure for ptosis was still effective. Surgical treatment of ptosis is very complex and requires precise indications. Appropriate management depends on the etiopathogenesis, accurate diagnosis, and clinical findings

Laboratory observations of slow earthquakes and the spectrum of tectonic fault slip modes

Slow earthquakes represent an important conundrum in earthquake physics. While regular earthquakes are catastrophic events with rupture velocities governed by elastic wave speed, the processes that underlie slow fault slip phenomena, including recent discoveries of tremor, slow-slip and low-frequency earthquakes, are less understood. Theoretical models and sparse laboratory observations have provided insights, but the physics of slow fault rupture remain enigmatic. Here we report on laboratory observations that illuminate the mechanics of slow-slip phenomena. We show that a spectrum of slow-slip behaviours arises near the threshold between stable and unstable failure, and is governed by frictional dynamics via the interplay of fault frictional properties, effective normal stress and the elastic stiffness of the surrounding material. This generalizable frictional mechanism may act in concert with other hypothesized processes that damp dynamic ruptures, and is consistent with the broad range of geologic environments where slow earthquakes are observed

On the evolution of elastic properties during laboratory stick-slip experiments spanning the transition from slow slip to dynamic rupture

The physical mechanisms governing slow earthquakes remain unknown, as does the relationship between slow and regular earthquakes. To investigate the mechanism(s) of slow earthquakes and related quasi-dynamic modes of fault slip we performed laboratory experiments on simulated fault gouge in the double direct shear configuration. We reproduced the full spectrum of slip behavior, from slow to fast stick slip, by altering the elastic stiffness of the loading apparatus (k) to match the critical rheologic stiffness of fault gouge (kc). Our experiments show an evolution from stable sliding, when k>kc, to quasi-dynamic transients when k ~ kc, to dynamic instabilities when k<kc. To evaluate the microphysical processes of fault weakening we monitored variations of elastic properties. We find systematic changes in P wave velocity (Vp) for laboratory seismic cycles. During the coseismic stress drop, seismic velocity drops abruptly, consistent with observations on natural faults. In the preparatory phase preceding failure, we find that accelerated fault creep causes a Vp reduction for the complete spectrum of slip behaviors. Our results suggest that the mechanics of slow and fast ruptures share key features and that they can occur on same faults, depending on frictional properties. In agreement with seismic surveys on tectonic faults our data show that their state of stress can be monitored by Vp changes during the seismic cycle. The observed reduction in Vp during the earthquake preparatory phase suggests that if similar mechanisms are confirmed in nature high-resolution monitoring of fault zone properties may be a promising avenue for reliable detection of earthquake precursors

Ultrastructure of neurovascular changes in human diabetic retinopathy

The previous concept regarding diabetic retinopathy assigned a primary role to hyperglycemia-induced microvascular alterations, while neuronal and glial abnormalities were considered to be secondary to either ischemia or exudation. The aim of this study was to reveal the potential role of neuronal and glial cells in initial and advanced alterations of the retinopathy in human type 2 diabetes. Electron microscopy and histochemical studies were performed on 38 surgically removed human eyes (28 obtained from diabetic patients and 10 from non-diabetic patients). Morphometric analysis of basement membrane material and lipids was performed. An accumulation of metabolic by-products was found in the capillary wall with aging: this aspect was significantly more pronounced in diabetics. Müller glial cells were found to contribute to alterations of the capillary wall and to occlusion, as well as to the development of proliferative retinopathy and cystoid degeneration of the retina. Our results showed morphological evidence regarding the role of neuronal and glial cells in the pathology of diabetic retinopathy, prior and in addition to microangiopathy. These morphological findings support a neurovascular pathogenesis at the origin of diabetic retinopathy, thus the current treatment approach should be completed by neuroprotective measures

Acquired ptosis associated with oculomotor and contralateral facial nerve synkinesis: the first reported case

Evidence of oculomotor nerve (ON) synkinesis is a common occurrence following both acquired and congenital III nerve palsy. It is generally accepted that aberrant regeneration is the likely aetiology of synkinesis in acquired III nerve palsy, following intracranial aneurysm, trauma, compressive neoplasms, cavernous sinus thrombosis and basilar meningitis

Approccio chirurgico e indicazioni ai trattamenti estetici nel dismorfismo da eccesso

Introduction. Patients with body dysmorphic disorder often go to the plastic surgeon to correct what they consider a physical deformity or defect, although their appearance falls within normal aesthetic standards. The aim of our study was to evaluate the real need for aesthetic treatments in such patients. Patients and methods. We included patients who practised an intense sport activity and believed they had body deformities ascribable to their sport activity. We evaluated whether the deformities described by the patients were real or exaggerated. The patients who did have a deformity underwent surgery to correct it; their level of satisfaction was evaluated at a 6-month follow-up examination. The patients with subjective deformities underwent a psychiatric examination. Results. We enrolled 51 patients who practised an intense sport activity and reported body deformities. Forty-one of these patients were found to have a body deformity upon examination and underwent surgery. Surgery was considered to be unnecessary in the remaining 10 patients. Thirty-two of the 41 patients who did undergo were highly satisfied with the outcome. Discussion. The plastic surgeon often sees patients with minor body deformities that do not require treatment but are a major cause of psychological disorders. A thorough psychiatric examination is necessary in such patients to rule out psychiatric diseases. The plastic surgeon should make every effort to identify patients with subjective body dysmorphic disorder to avoid the negative consequences due to the patient’s insatisfaction for the outcome of surgery

Trattamento della contrattura capsulare da impianto protesico mammario. Nostra esperienza

La più comune complicanza in pazienti sottoposte ad intervento chirurgico di impianto protesico mammario è la contrattura capsulare. Non esiste, attualmente, un trattamento standard efficace per questa complicanza. Lo scopo del presente articolo è illustrare la nostra esperienza sull’uso degli antagosisti dei recettori per i leucotrieni nel trattamento della contrattura capsulare. I risultati mostrano che l’utilizzo di questi farmaci è in grado di ridurre il dolore e la distorsione della mammella in pazienti con un lungo decorso di contrattura capsulare

Tecnica “a scaletta” nel trattamento delle perdite di sostanza del labbro inferiore

La patologia che con maggior frequenza colpisce il labbro inferiore è la patologia neoplastica, in particolar modo il carcinoma spinocellulare. L’approccio terapeutico di elezione è l’exeresi chirurgica ampia dalla quale possono derivare importanti alterazioni morfo-funzionali ed estetiche. Presso il Dipartimento di Chirurgia Plastica e Ricostruttiva del Policlinico Umberto I, “Sapienza” Università di Roma, dal 2005 al 2008 sono stati trattati 36 pazienti: 19 mediante escissione semplice (gruppo I) e 17 mediante la tecnica di Johanson (gruppo II), tutti sottoposti a follow-up a 6 e 12 mesi per valutate le alterazioni della funzionalità, la presenza/assenza di asimmetrie e la cicatrizzazione. Inoltre, ai pazienti è stata proposta una scheda di valutazione a punteggio costituita da 9 domande che indagano sia aspetti funzionali che estetici. Dai dati ottenuti è risultato che l’utilizzo del lembo di Johanson consente una radicalità oncologica non inferiore all’escissione semplice ma con migliori risultati funzionali ed estetici, una maggior soddisfazione da parte del paziente e tempi di degenza sovrapponibili

Dopamine D3 receptor modulates tissue type plasminogen activator (tPA) activity in mouse brain

Growing amount of evidence points to the dopamine D3 receptor (D3R) as an important mediator in the broad array of events that regulate memory function, perhaps through the modulation of molecular pathways involved in neurotrophic factor activation. Tissue type plasminogen activator (tPA) is a proteolytic enzyme that cleaves the precursor of brain derived neurotrophic factor (proBDNF) into the biologically active form of mature BDNF. However, whether D3Rs modulate tPA activity on BDNF in brain has not been ascertained yet. Here in the present study, using D3R knock-out (D3-/-) mice, we demonstrate that receptor inactivation is associated with increased tPA expression both in prefrontal cortex and, to a greater extent, in the hippocampus, two regions associated with memory processes. The heightened tPA levels observed in D3-/- mice inversely correlated with proBDNF protein expression, whereas they positively correlated with both BDNF mRNA and mature BDNF protein levels. In conclusion, our finding strongly suggest that D3Rs might modulate tPAmediated post-transcriptional processing of BDNF in brain regions critical to memory function