Microbial Heat and Organic Matter Loss in an Aerobic Corn Stover Storage Reactor: A Model Validation and Prediction Approach Using Lumped-Parameter Dynamical Formulation.

Corn stover dry matter loss effects variability for biofuel conversion facility and technology sustainability. This research seeks to understand the dynamic mechanisms of the thermal system, organic matter loss, and microbial heat generation in corn stover storage operations through system dynamics, a mathematical modeling approach, and response analysis to improve the system performance. This study considers epistemic uncertainties including cardinal temperatures of microbial respiratory activity, specific degradation rate, heat evolution per unit substrate degraded, and thermal conductivity in corn stover storage reactors. These uncertainties were managed through calibration, a process of improving the agreement between the computational and benchmark experimental results by adjusting the parameters of the model. Model calibration successfully predicted the temperature of the system as quantified by the mean absolute error, 0.6°C, relative to the experimental work. The model and experimental dry matter loss after 30 days of storage were 5.1% and 4.9 ± 0.28%. The model was further validated using additional experimental results to ensure that the model accurately represented the system. Model validation obtained a temperature mean absolute relative error of 0.9 ± 0.3°C and dry matter loss relative error of 3.1 ± 1.5%. This study presents a robust prediction of corn stover storage temperature and demonstrates that an understanding of carbon sources, microbial communities, and lag-phase evolution in bi-phasic growth are essential for the prediction of organic matter preservation in corn stover storage systems under environment's variation.

Controls of wellbore flow regimes on pump effluent composition.

Where well water and formation water are compositionally different or heterogeneous, pump effluent composition will vary due to partial mixing and transport induced by pumping. Investigating influences of purging and sampling methodology on composition variability requires quantification of wellbore flow regimes and mixing. As a basis for this quantification, analytical models simulating Poiseuille flow were developed to calculate flow paths and travel times. Finite element modeling was used to incorporate influences of mixing. Parabolic velocity distributions within the screened interval accelerate with cumulative inflow approaching the pump intake while an annulus of inflowing formation water contracts uniformly to displace an axial cylinder of pre-pumping well water as pumping proceeds. Increased dispersive mixing forms a more diffuse formation water annulus and the contribution of formation water to pump effluent increases more rapidly. Models incorporating viscous flow and diffusion scale mixing show that initially pump effluent is predominantly pre-pumping well water and compositions vary most rapidly. After two screen volumes of pumping, 94% of pump effluent is inflowing formation water. Where the composition of formation water and pre-pumping well water are likely to be similar, pump effluent compositions will not vary significantly and may be collected during early purging or with passive sampling. However, where these compositions are expected to be considerably different or heterogeneous, compositions would be most variable during early pumping, that is, when samples are collected during low-flow sampling. Purging of two screen volumes would be required to stabilize the content and collect a sample consisting of 94% formation water.

Midterm results of percutaneous endovascular treatment for acute and chronic deep venous thrombosis.

BACKGROUND: Treatment of deep venous thrombosis (DVT) with therapeutic anticoagulation has been increasingly challenged by aggressive percutaneous treatment using ultrasound-accelerated catheter-directed thrombolysis (US-CDT) or percutaneous pharmacomechanical thrombectomy (PMT). These techniques have been promoted to improve thrombus removal, prolong venous patency, prevent venous insufficiency, and reduce postthrombotic syndrome. This study reviews midterm results using these endovascular techniques for both acute and chronic DVT. METHODS: A retrospective chart review was performed on patients treated for acute or chronic DVT with US-CDT and/or PMT. Charts were reviewed for patient demographics, medical history and treatment, operative details, and postoperative outcomes. Intraoperative venography and intravascular ultrasound quantified clot response to therapy. Duplex ultrasound defined the pre- and postoperative extent of venous thrombosis, venous patency, and valvular function. RESULTS: Between October 1, 2002 and September 30, 2010, 80 patients were treated for iliofemoral (n = 48), iliofemoropopliteal (n = 15), or femoropopliteal (n = 17) venous thrombosis. Mean age was 45.8 years (range, 15-78 years), and 24 patients (30%) had a documented history of hypercoagulable state. Intravascular ultrasound confirmed May-Thurner syndrome in 34 patients (42.5%). Fifty-two patients (65%) were treated for acute DVT; the mean time to intervention from symptom onset was 8.7 ± 4.5 days (range, 1-14 days). The remaining 28 patients (35%) had chronic symptoms and were treated at a mean of 8.6 ± 10.9 months (range, 1.5-36 months) after DVT diagnosis was made. Patients were treated with PMT (n = 43, 53.8%), US-CDT (n = 14, 17.5%), or both (n = 32, 28.7%). Clot lysis (>90%) was achieved in 72 of 80 patients (90%). Tenecteplase was used for all cases, and the mean dose was 8.6 ± 4.3 mg. Adjunctive procedures, including angioplasty with or without stent placement, were required in 90% (n = 47) of acute patients and in 96% (n = 27) of chronic patients (P = .33). Three patients (3.8%) had postoperative bleeding events requiring blood transfusion; there were no occurrences of intracranial hemorrhage or clinically significant pulmonary embolism. At a mean follow-up of 3.8 years (range, 1-8.9 years), venous patency was present in 49 of 52 acute patients (94%) and in 23 of 28 chronic patients (82%) (P = .12). Valve function was preserved in 41 of 52 (79%) acute patients vs 11 of 28 (39%) chronic patients (P < .001). CONCLUSIONS: US-CDT and PMT can effectively remove acute and chronic thrombus in the lower extremity deep venous system. Vein patency and valvular function is better preserved at midterm follow-up after treatment for acute DVT, however intervention should be considered in patients with chronic DVT as well.

Longitudinal changes in kidney parenchymal volume associated with renal artery stenting.

OBJECTIVE: This study assessed the longitudinal changes in renal volume after renal artery stenting (RAS) to determine if renal mass is preserved by stenting. METHODS: The study cohort consisted of 38 patients with longitudinal imaging available for renal volume quantification before and after RAS. Renal volume was estimated as (kidney length) × (width) × (depth/2) based on preoperative renal imaging. For each patient, the clinical response of blood pressure (BP) and renal function to RAS was categorized according to modified American Heart Association guidelines. Changes in renal volume were assessed using paired nonparametric analyses. RESULTS: The cohort was a median age of 69 years (interquartile range [IQR], 60-74 years). A favorable BP response was observed in 11 of 38 patients (28.9%). At a median interval between imaging studies of 21 months (IQR, 13-32 months), ipsilateral renal volume was significantly increased from baseline (146.8 vs 133.8 cm(3);P = .02). This represents a 6.9% relative increase in ipsilateral kidney volume from baseline. A significant negative correlation between preoperative renal volume and the relative change in renal volume postoperatively (r = -0.42; P = .0055) suggests that smaller kidneys experienced the greatest gains in renal volume after stenting. It is noteworthy that the 25 patients with no change in BP or renal function-clinical failures using traditional definitions-experienced a 12% relative increase in ipsilateral renal volume after RAS. Multivariate analysis determined that stable or improved renal volume after stenting was an independent predictor of stable or improved long-term renal function (odds ratio, 0.008; 95% confidence interval, 0.000-0.206; P = .004). CONCLUSIONS: These data lend credence to the belief that RAS preserves renal mass in some patients. This benefit of RAS even extends to those patients who would be considered treatment failures by traditional definitions. Patients with stable or increased renal volume after RAS had more stable renal function during long-term follow-up, whereas patients with renal volume loss after stenting were prone to deterioration of renal function.

Hand ischemia associated with elbow trauma in children.

OBJECTIVES: Previous observational studies suggest that children with hand ischemia following elbow trauma can be safely observed if Doppler signals are present in the wrist arteries (pink pulseless hand, PPH). Nonoperative management of PPH is predicated on the assumption that PPH results from local arterial spasm, but the mechanism of arterial compromise has not been investigated. We hypothesized that PPH signifies a brachial artery injury that requires surgical repair. METHODS: Retrospective review of operations performed on children with hand ischemia following elbow trauma at a level I trauma center pediatric hospital. RESULTS: Between 2003 and 2010, 12 children (seven males, mean age 7.4 years) underwent brachial artery exploration for hand ischemia following elbow trauma (11 supracondylar fractures, one elbow dislocation) due to falls (n = 10) or motor vehicle crashes (n = 2). At presentation, three subjects had normal radial pulses, eight subjects had Doppler signals but no palpable pulses, and one had weak Doppler flow with advanced hand ischemia. Six of the nine subjects without palpable pulses also had neurosensory changes. All 12 subjects underwent brachial artery exploration either initially (n = 2) or following orthopedic fixation (n = 10) due to persistent pulselessness. At operation, eight of 12 patients (67%) had focal brachial artery thrombosis due to intimal flaps, and four had brachial artery and median nerve entrapment within the pinned fracture site. At discharge, all 12 subjects had palpable radial pulses, but three with entrapment had dense median nerve deficits. One of the three subjects with dense neurologic deficit had complete recovery of neurologic function at ten months. The other two subjects had residual median nerve deficits with partial recovery at 5 and 6 months follow-up, respectively. No patient developed Volkman's contracture. CONCLUSIONS: Brachial artery injuries should be anticipated in children with hand ischemia associated with elbow trauma. Neurovascular entrapment at the fracture site is a possible complication of orthopedic fixation. Absence of palpable wrist pulses after orthopedic fixation should prompt immediate brachial artery exploration. PPH should not be considered a consequence of arterial spasm in these patients.