Geotechnical characterization of mixed sandy and silty soils using piezocone tests: Analysis of partial drainage phenomena and rate effects on the experimental soil response

The cone penetration test (CPT), together with its recent variation (CPTU), has become the most widely used in-situ testing technique for soil profiling and geotechnical characterization. The knowledge gained over the last decades on the interpretation procedures in sands and clays is certainly wide, whilst very few contributions can be found as regards the analysis of CPT(u) data in intermediate soils. Indeed, it is widely accepted that at the standard rate of penetration (v = 20 mm/s), drained penetration occurs in sands while undrained penetration occurs in clays. However, a problem arise when the available interpretation approaches are applied to cone measurements in silts, sandy silts, silty or clayey sands, since such intermediate geomaterials are often characterized by permeability values within the range in which partial drainage is very likely to occur. Hence, the application of the available and well-established interpretation procedures, developed for ‘standard’ clays and sands, may result in invalid estimates of soil parameters. This study aims at providing a better understanding on the interpretation of CPTU data in natural sand and silt mixtures, by taking into account two main aspects, as specified below: 1)Investigating the effect of penetration rate on piezocone measurements, with the aim of identifying drainage conditions when cone penetration is performed at a standard rate. This part of the thesis has been carried out with reference to a specific CPTU database recently collected in a liquefaction-prone area (Emilia-Romagna Region, Italy). 2)Providing a better insight into the interpretation of piezocone tests in the widely studied silty sediments of the Venetian lagoon (Italy). Research has focused on the calibration and verification of some site-specific correlations, with special reference to the estimate of compressibility parameters for the assessment of long-term settlements of the Venetian coastal defences.

Drainage of thin aqueous films between solid surfaces measured with the colloidal probe technique

Understanding liquid flow at the vicinity of solid surfaces is crucial to the developmentrnof technologies to reduce drag. One possibility to infer flow properties at the liquid-solid interface is to compare the experimental results to solutions of the Navier-Stokes equations assuming the no-slip boundary condition (BC) or the slip BC. There is no consensus in the literature about which BC should be used to model the flow of aqueous solutions over hydrophilic surfaces. Here, the colloidal probe technique is used to systematically address this issue, measuring forces acting during drainage of water over a surface. Results show that experimental variables, especially the cantilever spring constant, lead to the discrepancy observed in the literature. Two different parameters, calculated from experimental variables, could be used to separate the data obtained in this work and those reported in the literature in two groups: one explained with the no-slip BC, and another with the slip BC. The observed residual slippage is a function of instrumental variables, showing a trend incompatible with the available physical justifications. As a result, the no-slip is the more appropriate BC. The parameters can be used to avoid situations where the no-slip BC is not satisfied.

Refractory Hematuria in an Oliguric Patient After Pancreas Transplantation with Exocrine Pancreas Bladder Drainage

A 52-yr-old man presented with hematuria and clot retention. He had undergone simultaneous pancreas-kidney transplantation with exocrine pancreas bladder drainage 16 yr ago. The patient suffered from progressive transplant kidney failure with gradually decreasing urine output and needed hemodialysis every other day. Gross hematuria persisted after removal of all blood clots. Cystoscopy showed multiple small, flat ulcers of the bladder mucosa. Some bled discretely and were coagulated cautiously. However, hematuria was refractory to multiple urological interventions, which eventually necessitated an enteric diversion of the exocrine pancreas. Hematuria ceased following an uneventful postoperative course.

Efficacy of silver-bearing external ventricular drainage catheters: a retrospective analysis

Catheter-related infection of CSF is a potentially life-threatening complication of external ventricular drainage (EVD). When using EVD catheters, contact between the ventricular system and skin surface occurs and CSF infection is possible. The aim of this analysis was to compare the efficacy of silver-bearing EVD catheters for reducing the incidence of infection with standard nonimpregnated EVD catheters in neurosurgical patients with acute hydrocephalus.

Abandoned Coal Mine Drainage and Its Remediation: Impacts on Stream Ecosystem Structure and Function

The effects of abandoned mine drainage (AMD) on streams and responses to remediation efforts were studied using three streams (AMD-impacted, remediated, reference) in both the anthracite and the bituminous coal mining regions of Pennsylvania (USA). Response variables included ecosystem function as well as water chemistry and macroinvertebrate community composition. The bituminous AMD stream was extremely acidic with high dissolved metals concentrations, a prolific mid-summer growth of the filamentous alga, Mougeotia, and .10-fold more chlorophyll than the reference stream. The anthracite AMD stream had a higher pH, substrata coated with iron hydroxide(s), and negligible chlorophyll. Macroinvertebrate communities in the AMD streams were different from the reference streams, the remediated streams, and each other. Relative to the reference stream, the AMD stream(s) had (1) greater gross primary productivity (GPP) in the bituminous region and undetectable GPP in the anthracite region, (2) greater ecosystem respiration in both regions, (3) greatly reduced ammonium uptake and nitrification in both regions, (4) lower nitrate uptake in the bituminous (but not the anthracite) region, (5) more rapid phosphorus removal from the water column in both regions, (6) activities of phosphorus-acquiring, nitrogenacquiring, and hydrolytic-carbon-acquiring enzymes that indicated extreme phosphorus limitation in both regions, and (7) slower oak and maple leaf decomposition in the bituminous region and slower oak decomposition in the anthracite region. Remediation brought chlorophyll concentrations and GPP nearer to values for respective reference streams, depressed ecosystem respiration, restored ammonium uptake, and partially restored nitrification in the bituminous (but not the anthracite) region, reduced nitrate uptake to an undetectable level, restored phosphorus uptake to near normal rates, and brought enzyme activities more in line with the reference stream in the bituminous (but not the anthracite) region. Denitrification was not detected in any stream. Water chemistry and macroinvertebrate community structure analyses capture the impact of AMD at the local reach scale, but functional measures revealed that AMD has ramifications that can cascade to downstream reaches and perhaps to receiving estuaries.

Is the use of antibiotic-impregnated external ventricular drainage beneficial in the management of iatrogenic ventriculitis?

Profound evidence substantiates significantly reduced risk of catheter-related infections with prophylactic use of rifampin- and clindamycin-impregnated silicone catheters (Bactiseal(®), Codman Johnson & Johnson, Raynham, MA, USA) for external ventricular drainage (EVD). However, whether Bactiseal(®)-EVD (B-EVD) influences the treatment of EVD-related ventriculitis remains controversial.

[Hyperinsulinemia as a consequence of systemic venous drainage in patients with pancreas transplantation]

To evaluate the metabolic consequences of pancreatic transplantation with systemic venous drainage on beta cell function, we examined insulin and C-peptide responses to arginine and secretin in type I diabetic recipients of pancreas transplantation (n = 16), and normal controls (n = 28). Basal insulin levels were 24 +/- 3 microU/l in pancreas recipients, and 7 +/- 1 microU/l in controls (p less than 0.001). Stimulated insulin levels following arginine (MANOVA, p less than 0.001), and secretin (MANOVA, p less than 0.001) were 1.5 to 3 fold elevated compared to controls. In contrast, integrated C-peptide responses following stimulation with arginine or secretin did not differ significantly between the two groups. We conclude that recipients of pancreas allografts with systemic venous drainage have elevated basal and stimulated insulin levels and that these alterations are primarily due to alterations of first pass hepatic insulin clearance although insulin resistance secondary to immunosuppressive therapy (including prednisone) may also play a contributing role. To avoid hyperinsulinemia and its possible long term adverse consequences, transplantation of pancreas allografts in sites with portal rather than systemic venous drainage may be preferable.

Systemic venous drainage of pancreas allografts as independent cause of hyperinsulinemia in type I diabetic recipients

To evaluate the metabolic consequences of pancreas transplantation with systemic venous drainage on beta-cell function, we examined insulin and C-peptide responses to glucose and arginine in type I (insulin-dependent) diabetic pancreas recipients (n = 30), nondiabetic kidney recipients (n = 8), and nondiabetic control subjects (n = 28). Basal insulin levels were 66 +/- 5 pM in control subjects, 204 +/- 18 pM in pancreas recipients (P less than 0.0001 vs. control), and 77 +/- 17 pM in kidney recipients. Acute insulin responses to glucose were 416 +/- 44 pM in control subjects, 763 +/- 91 pM in pancreas recipients (P less than 0.01 vs. control), and 589 +/- 113 pM in kidney recipients (NS vs. control). Basal and stimulated insulin levels in two pancreas recipients with portal venous drainage were normal. Integrated acute C-peptide responses were not statistically different (25.3 +/- 4.3 nM/min in pancreas recipients, 34.2 +/- 5.5 nM/min in kidney recipients, and 23.7 +/- 2.1 nM/min in control subjects). Similar insulin and C-peptide results were obtained with arginine stimulation, and both basal and glucose-stimulated insulin-C-peptide ratios in pancreas recipients were significantly greater than in control subjects. We conclude that recipients of pancreas allografts with systemic venous drainage have elevated basal and stimulated insulin levels and that these alterations are primarily due to alterations of first-pass hepatic insulin clearance, although insulin resistance secondary to immunosuppressive therapy (including prednisone) probably plays a contributing role. To avoid hyperinsulinemia and its possible long-term adverse consequences, transplantation of pancreas allografts into sites with portal rather than systemic venous drainage should be considered.

Roux-en-Y drainage of the pancreatic stump decreases pancreatic fistula after distal pancreatic resection

Clinically relevant fistula after distal pancreatic resection occurs in 5-30% of patients, prolonging recovery and considerably increasing in-hospital stay and costs. We tested whether routine drainage of the pancreatic stump into a Roux-en-Y limb after distal pancreatic resection decreased the incidence of fistula. From October 2001, data of all patients undergoing pancreatic distal resection were entered in a prospective database. From June 2003 after resection, the main pancreatic duct and the pancreatic stump were oversewn, and in addition, anastomosed into a jejunal Roux-en-Y limb by a single-layer suture (n = 23). A drain was placed near the anastomosis, and all patients received octreotide for 5-7 days postoperatively. The volume of the drained fluid was registered daily, and concentration of amylase was measured and recorded every other day. Patient demographics, hospital stay, pancreatic fistula incidence (> or =30 ml amylase-rich fluid/day on/after postoperative day 10), perioperative morbidity, and follow-up after discharge were compared with our initial series of patients (treated October 2001-May 2003) who underwent oversewing only (n = 20). Indications, patient demographics, blood loss, and tolerance of an oral diet were similar. There were four (20%) pancreatic fistulas in the "oversewn" group and none in the anastomosis group (p < 0.05). Nonsurgical morbidity, in-hospital stay, and follow-up were comparable in both groups.

Restoration of forest wetlands: Case studies in Michigan and Finland

Forested wetlands throughout the world are valuable habitats; especially in relatively species-poor northern regions, they can be considered biological hotspots. Unfortunately, these areas have been degraded and destroyed. In recent years, however, the biological importance of wetlands has been increasingly recognized, resulting in the desire to restore disturbed habitats or create in place of destroyed ones. Restoration work is taking place across the globe in a diversity of wetland types, and research must be conducted to determine successful techniques. As a result, two studies of the effects of wetland restoration and creation were conducted in forested wetlands in northern Michigan and southern Finland. In North America, northern white-cedar wetlands have been declining in area, despite attempts to regenerate them. Improved methods for successfully establishing northern white-cedar are needed; as a result, the target of the first study was to determine if creating microtopography could be beneficial for white-cedar recruitment and growth. In northern Europe, spruce swamp forests have become a threatened ecosystem due to extensive drainage for forestry. As part of the restoration of these habitats, i.e. rewetting through ditch blocking, Sphagnum mosses are considered to be a critical element to re-establish, and an in-depth analysis of how Sphagnum is responding to restoration in spruce swamp forests has not been previously done. As a result, the aim of the second study was to investigate the ecophysiological functioning of Sphagnum and feather mosses across a gradient of pristine, drained, and restored boreal spruce swamp forests.