Experimental and numerical investigations to assess the behaviour of a buried pipeline in areas with high geological instability

Ground displacements such as landslides, fault movements, soil liquefaction which may be caused by seismic activity are one of the most dangerous phenomena that can involve buried pipelines, e.g. for oil and gas transportation, or water and sewage. This aspect is currently an important part of research and a challenge for lifelines owners that are interested in prevent or limit pipeline damages. Within the framework of GIPIPE1 research program (SAFETY OF BURIED STEEL PIPELINES UNDER GROUND-INDUCED DEFORMATIONS) new full-scale facilities have been developed and adopted in order to investigate pipe-soil interaction mechanism (in particular sand and 8” 5/8 X65 steel pipes). The new experimental facilities have been designed to perform two groups of tests: simple interaction tests (axial pullout and transversal pullout test) and complex interaction tests (reproducing a pipeline crossing landslide). A system of steel containers (stationary and fixed) in which pipe samples are buried within the sand, have been assembled. Numerical analyses have been performed using strength parameters of sand and steel obtained from laboratory testing and subsequently validated by means full-scale experimental results. The outcomes of the experimental activity showed some differences in soil reaction on pipe by increasing the relative density of soil filling and using a smoother coating. Moreover peak soil resistances estimated with equations suggested by ASCE guidelines [4] cannot predict satisfactory measured axial and lateral soil reactions. This is a confirmation of previous studies in which was evidenced the effect of soil dilation in the annular soil zone around the pipe during axial relative movement between pipe and soil causes an increase of the normal stress at pipe soil interface, in particular the horizontal direction is significantly constrained by the surrounding soil mass leading to an higher increase in lateral soil stress in this direction respect to the vertical direction. Therefore this phenomenon leads to a lateral earth pressure coefficient K which is greater than K0 (coefficient of pressure at rest) as suggested in the ASCE guidelines [4], therefore for a better estimation of soil response using that equation it is suggested to measure the ratio between horizontal stress and the vertical stress during a full-scale axial pullout test. Pipes submitted to lateral soil displacement with a constrained uplifting show as expected a greater soil reaction than that estimated by ASCE [4] and PRCI [20]. As far as the landslide/fault test are concerned, the maximum soil relative density (Dr) achieved during experimental tests performed in this study was around 40%. This level of density led to a low stiffness of soil mass hence a limited global deformation of a 24 m embedded pipe during landslide/fault tests in which one caisson was moved up to 4 m respect to the initial position. These experimental findings confirm that sand with a low value of maximum achievable density may prevent from high loads developing on pipelines, in contrast to native soil which can apply higher loads. Numerical analyses and their validation gave us a suitable instrument to estimate the pipe soil response for large ground displacements phenomena

Spontaneous intracranial hypotension : two steroid-responsive cases

Purpose: Spontaneous intracranial hypotension (SIH) is characterised by orthostatic headache, low cerebrospinal fluid pressure and diffuse pachymeningeal enhancement after intravenous gadolinium contrast administration. Magnetic resonance imaging (MRI) often plays a crucial role for correct diagnosis. Case description: We described two similar cases of SIH, whose clinical and imaging features are typical for this pathology. At MRI brain scan, both patients showed diffuse and intense pachymeningeal enhancement and moderate venous distension and epidural vein engorgement. The two patients were treated with bed rest and oral steroid therapy, with complete and long-lasting symptomatic relief. Conclusions: Orthostatic nature of headache is the most indicative clinical feature suggesting SIH; contrast-enhanced MRI provides definite imaging diagnostic findings. Conservative treatment coupled to steroid therapy is often sufficient to obtain complete disappearance of symptoms

Sigh in patients with acute hypoxemic respiratory failure and acute respiratory distress syndrome: the PROTECTION pilot randomized clinical trial

Background: Sigh is a cyclic brief recruitment manoeuvre: previous physiological studies showed that its use could be an interesting addition to pressure support ventilation to improve lung elastance, decrease regional heterogeneity and increase release of surfactant. Research question: Is the clinical application of sigh during pressure support ventilation (PSV) feasible? Study design and methods: We conducted a multi-center non-inferiority randomized clinical trial on adult intubated patients with acute hypoxemic respiratory failure or acute respiratory distress syndrome undergoing PSV. Patients were randomized to the No Sigh group and treated by PSV alone, or to the Sigh group, treated by PSV plus sigh (increase of airway pressure to 30 cmH2Ofor 3 seconds once per minute) until day 28 or death or successful spontaneous breathing trial. The primary endpoint of the study was feasibility, assessed as non-inferiority (5% tolerance) in the proportion of patients failing assisted ventilation. Secondary outcomes included safety, physiological parameters in the first week from randomization, 28-day mortality and ventilator-free days. Results: Two-hundred fifty-eight patients (31% women; median age 65 [54-75] years) were enrolled. In the Sigh group, 23% of patients failed to remain on assisted ventilation vs. 30% in the No Sigh group (absolute difference -7%, 95%CI -18% to 4%; p=0.015 for non-inferiority). Adverse events occurred in 12% vs. 13% in Sigh vs. No Sigh (p=0.852). Oxygenation was improved while tidal volume, respiratory rate and corrected minute ventilation were lower over the first 7 days from randomization in Sigh vs. No Sigh. There was no significant difference in terms of mortality (16% vs. 21%, p=0.342) and ventilator-free days (22 [7-26] vs. 22 [3-25] days, p=0.300) for Sigh vs. No Sigh. Interpretation: Among hypoxemic intubated ICU patients, application of sigh was feasible and without increased risk

High b-Value Diffusion MRI to Differentiate Recurrent Tumors from Posttreatment Changes in Head and Neck Squamous Cell Carcinoma: A Single Center Prospective Study

Recently DW-MR Imaging has shown promising results in distinguishing between recurrent tumors and posttreatment changes in Head and Neck Squamous Cell Carcinoma (HNSSC). Aim of this study was to evaluate the diagnostic performances of DWI at high b-value (b = 2000 s/mm 2 ) compared to standard b-value (b = 1000 s/mm 2 ) and ADC ratio values (ADC ratio = ADC 2000 /ADC 1000 ×100) to differentiate recurrent tumors from posttreatment changes after treatment of HSNCC. 20 patients (16 M, 4 F) underwent MR Imaging between 2 and 16 months (mean 7) after treatment. Besides morphological sequences, we performed single-shot echoplanar DWI at b = 1000 s/mm 2 and b = 2000 s/mm 2 , and corresponding ADC maps were generated (ADC 1000 and ADC 2000 , resp.). By considering contrast-enhanced T1-weighted images as references, ROIs were drawn in order to evaluate mean ADC 1000 , ADC 2000 , and ADC ratio . The mean ADC 1000 and ADC 2000 in recurrent tumors were significantly lower than those in posttreatment changes ( = 0.001 and = 0.016, resp.). Moreover, the mean ADC ratio between the two groups showed a statistically significant difference ( = 0.002). Sensitivity, specificity, and accuracy of ADC ratio were 82.0%, 100%, and 90%, respectively, by considering an optimal cutoff value of 65.5%. ADC ratio is a promising value to differentiate between recurrent tumors and posttreatment changes in HNSCC and may be more useful than ADC 1000 and ADC 2000

High b-Value Diffusion MRI to Differentiate Recurrent Tumors from Posttreatment Changes in Head and Neck Squamous Cell Carcinoma: A Single Center Prospective Study

Recently DW-MR Imaging has shown promising results in distinguishing between recurrent tumors and posttreatment changes in Head and Neck Squamous Cell Carcinoma (HNSSC). Aim of this study was to evaluate the diagnostic performances of DWI at high b-value (b = 2000 s/mm2) compared to standard b-value (b = 1000 s/mm2) and ADCratio values (ADCratio=ADC2000/ADC1000×100) to differentiate recurrent tumors from posttreatment changes after treatment of HSNCC. 20 patients (16 M, 4 F) underwent MR Imaging between 2 and 16 months (mean 7) after treatment. Besides morphological sequences, we performed single-shot echo-planar DWI at b = 1000 s/mm2 and b = 2000 s/mm2, and corresponding ADC maps were generated (ADC1000 and ADC2000, resp.). By considering contrast-enhanced T1-weighted images as references, ROIs were drawn in order to evaluate mean ADC1000, ADC2000, and ADCratio. The mean ADC1000 and ADC2000 in recurrent tumors were significantly lower than those in posttreatment changes (P=0.001 and P=0.016, resp.). Moreover, the mean ADCratio between the two groups showed a statistically significant difference (P=0.002). Sensitivity, specificity, and accuracy of ADCratio were 82.0%, 100%, and 90%, respectively, by considering an optimal cutoff value of 65.5%. ADCratio is a promising value to differentiate between recurrent tumors and posttreatment changes in HNSCC and may be more useful than ADC1000 and ADC2000