Dissolved air (pressure) flotation

It appears that, in the past, little attempt has been made to establish the basic parameters influencing the flotation process, or their inter-relationships, on a quantitative basis for the purpose of developing rational design procedures. This thesis investigates those parameters influencing solids removal and thickening by dissolved-air (pressure) flotation and the criteria pertaining to the design of flotation tanks for solids removal and thickening. A review of pertinent literature on flotation is presented. The historical development of flotation is given together with the theory of bubble-particle adhesion. Four common methods of flotation are compared and their inherent advantages and disadvantages are discussed. Dissolved-air (pressure) flotation, the method used in this investigation, is considered in greater detail by presenting established practical considerations for design. A pressure-saturation unit was developed in which all the compressed air supplied is dissolved into the saturator feed by continously recycling the air through a sparger, i.e. there is no air wastage. The air circulating pump operates within the pressurized circuit so that it pumps only against the hydrostatic head of water in the saturator. A vertical flow type flotation unit was developed which provides a counter current flow regime and a stable interface between the clear liquid and rising agglomerates. The accumulated agglomerates discharge freely and without mechanical assistance at the top of the unit

Collecting qualitative data via video statements in the digital era

Qualitative research methods in organisational research, such as interviews, observation and focus groups, provide detailed insights into business phenomena. In the social sciences, new methods have emerged enabled by the digital era, such as video methods particularly suitable for capturing participant interaction and obtaining non-verbal cues. Slowly, video methods are also gaining recognition in organisational research, opening up innovative possibilities for applying them beyond the traditional focus purely on interaction. This research presents an alternative video method: video statements. This time- and cost-efficient data collection method is characterised by participants who self-record their experiences following a guideline to gather multimodal (visual, audio and textual) data. Hence, video statements can be collected remotely. In our sample study, the approach generates genuine impressions, providing insights into an emerging organisational phenomenon. The output is used as a form of data and a basis for follow-up discussion by participants to add meaning to the video representations. Overall, video statements offer an alternative approach to data collection, supporting researchers in providing richer knowledge for business and management

Aortic Morphology Following Endovascular Repair of Acute and Chronic Type B Aortic Dissection: Implications for Management

AbstractObjectiveThe study aimed to define early clinical outcomes, and medium term morphological changes, following endovascular treatment of acute (AAD) and chronic (CAD) Type B aortic dissections.Main outcomesThe cohort comprised 78 patients who underwent endovascular repair for AAD (38) and CAD (40). Early and late clinical outcomes were prospectively recorded. All patients underwent serial follow up with CT scanning. False lumen thrombosis rates, true, false and total aortic short axis diameter were recorded at the mid point of the endograft and below this level in the thoracic aorta. The total maximum aortic diameter in the thoracic, abdominal aorta was quantified.ResultsThe 30-d mortality was 2.6% in AAD and 7.5% in CAD. The 30-d stroke and paraplegia rates were 5.3% and 0% in AAD. There were no cases of stroke or paraplegia in patients with CAD. At 30 months follow up, the cumulative survival for the two groups was 93% for AAD and 66.5% for CAD (P=0.015, Kaplan Meier) and the cumulative re-intervention rate was 62% and 55% in AAD and CAD respectively (P=0.961, Kaplan-Meier). False lumen thrombosis rates were equivalent in the two groups and were higher at the level of the endograft than below this level (P<0.05). Aortic remodelling was greater in AAD, whereas the aortic dimensions after treatment of CAD remained relatively static. Up to 20% of patients in both groups demonstrated enlargement of the thoracic aorta.ConclusionsThe data support the use of endovascular repair of the thoracic aorta in Type B aortic dissection. 30-d outcomes are acceptable. Patients with AAD demonstrate significant aortic remodelling whereas patients with CAD do not. This has significant implications for practice as patients with CAD must rely on maintenance of false lumen thrombosis to preserve the integrity of the endovascular repair

Device-specific Outcomes Following Endovascular Aortic Aneurysm Repair

AbstractObjectiveTo compare aneurysm morphology, initial outcomes and mid-term results in patients receiving Talent or Zenith grafts for elective endovascular aneurysm repair (EVR).MethodsOver a 6-year time period ending in 2007, 286 patients underwent elective EVR of infra-renal abdominal aortic aneurysms using Talent or Zenith devices. Patient demographics, aneurysm morphology and initial outcomes (primary-assisted technical success rates, 30-day limb occlusion, re-intervention and mortality) were compared using chi-squared tests or Student's t-tests. Kaplan–Meier curves were calculated to compare cumulative rates of freedom from type I or III endoleak, re-intervention, endograft patency and overall survival over mid-term follow-up.ResultsAdverse aneurysm morphology was more common in patients receiving Zenith stent grafts, with a greater proportion of shorter neck lengths (<10mm, 12.9% vs 0%; p≤0.001) and severe neck angulation (>60°, 25.0% vs 10.3%; p=0.002). Equivalent primary-assisted technical success rates were achieved with both Talent and Zenith grafts (94.0% vs 96.1%; p=0.41). A significant number of adjunctive procedures were required in both groups to obtain a proximal endograft seal, with relatively more procedures performed in the Talent group (28.6% vs 12.4%; p=0.003). Early outcomes were similar for 30-day re-intervention (5.3% vs 3.9%; p=0.91), 30-day limb occlusion (1.5% vs 2.6%; p=0.51), 30-day morbidity (6.8% vs 11.8%; p=0.15) and 30-day mortality (4.5% vs 3.9%; p=0.80).The cumulative incidence of freedom from re-intervention was 88.3±2.9%, 86.1±3.3% and 84.1±3.9% at 1, 2 and 3 years respectively. There were no significant differences between Talent and Zenith groups for re-intervention, type I or III endoleak or limb occlusion rates over the same time period. Overall patient survival was 88.4±2.85% at 1 year, 83.7±4.0% at 2 years and 78.9±5.5% at 3 years.ConclusionsEquivalent primary-assisted technical success rates can be achieved using either Talent or Zenith endografts for endovascular aneurysm repair, but operating teams should be prepared to perform additional adjunctive procedures to obtain a primary proximal seal with either stent. The Zenith endograft performed well in the context of less favourable pre-operative aneurysm morphology. Both Talent and Zenith endografts appeared equally durable in the medium term

Report of a case of ischemic colitis with bilaterally patent internal iliac arteries after endovascular abdominal aneurysm repair

During endovascular aneurysm repair (EVAR), interruption of the internal iliac arteries (IIAs) or the inferior mesenteric artery by stents or embolization is thought to cause colon ischemia. To minimize this risk, attempts have been made to preserve the IIAs using iliac branch devices or IIA revascularization. Here we present our experience of colon ischemia after EVAR in a patient with bilaterally patent IIAs without evidence of embolism. A 70-year-old man had abdominal pain and a ruptured abdominal aortic aneurysm was found. We performed EVAR with custom-made tube grafts preserving the bilateral IIAs. On postoperative day 2, the patient complained of abdominal pain, a sigmoidoscopy was performed revealing colon ischemia. On laparotomy, transmural infarction of the sigmoid colon was found and resected. Because IIA preservation cannot guarantee protection against colon ischemia, surgeons should maintain a high level of suspicion and use surveillance liberally after EVAR for early diagnosis of colon ischemia, even if both IIAs are preserved

Endovascular treatment of visceral artery aneurysms and pseudoaneurysms with stent-graft: Analysis of immediate and long-term results

The aim of this study is to analyze the safety and efficacy of stent-graft endovascular treatment for visceral artery aneurysms and pseudoaneurysms. METHODS: Multicentric retrospective series of patients with visceral aneurysms and pseudoaneurysms treated by means of stent graft. The following variables were analyzed: Age, sex, type of lesion (aneurysms/pseudoaneurysms), localization, rate of success, intraprocedural and long term complication rate (SIR classification). Follow-up was performed under clinical and radiological assessment. RESULTS: Twenty-five patients (16 men), with a mean age of 59 (range 27-79), were treated. The indication was aneurysm in 19 patients and pseudoaneurysms in 6. The localizations were: splenic artery (12), hepatic artery (5), renal artery (4), celiac trunk (3) and gastroduodenal artery (1). Successful treatment rate was 96% (24/25 patients). Intraprocedural complication rate was 12% (4% major; 8% minor). Complete occlusion was demonstrated during follow up (mean 33 months, range 6-72) in the 24 patients with technical success. Two stent migrations (2/24; 8%) and 4stent thrombosis (4/24; 16%) were detected. Mortality rate was 0%. CONCLUSION: In our study, stent-graft endovascular treatment of visceral aneurysmns and pseudoaneurysms has demonstrated to be safe and is effective in the long-term in both elective and emergent cases, with a high rate of successful treatment and a low complication rate

The outcomes of educational welfare officer contact in England

The key purpose of educational welfare officers in England is to support students and parents to maximise educational opportunities for young people. However more is known about their role in relation to school attendance than in relation to pupils’ educational outcomes. Using the Longitudinal Survey of Young People in England (LSYPE), this paper investigates the characteristics of teenagers who received educational welfare contact because of their behaviour between 2004 and 2006. With observational data it is often difficult to isolate respondents exposed to a particular intervention or ‘treatment’, because of non-random allocation. We address this using inverse-probability-weighted regression adjustment (IPWRA) to estimate more accurately the effect of educational welfare contact on outcomes of educational achievement and aspiration. Our findings indicate that young people who had educational welfare contact because of their behaviour were less likely to apply to university, less confident in university acceptance if they applied and had lower odds of achieving five General Certificate of Secondary Education at grades A*–C, the government benchmark for education achievement at age 16. We discuss the limitations we face and implications of these findings for future research

Coagulation of dissolved organic matter in surface water by novel titanium (III) chloride: Mechanistic surface chemical and spectroscopic characterisation

Problems caused by residual organics in treated water include the formation of disinfection by-products (DBP) following reaction with chlorine and being a substrate for microbial regrowth in the drinking water distribution system. Dissolved organic matter (DOM) can only be partially removed by conventional treatment process i.e. coagulation by Al- and Fe-based salts. In the present study, the performance of titanium trichloride (TiCl3) as a coagulant for surface water treatment was studied and compared with conventionally used aluminum sulfate (alum). Jar test experiments were performed at various coagulant doses and pH levels to determine the optimum conditions based on removal efficiencies of dissolved organic carbon (DOC). The zeta potential values were analysed for assessing the destabilisation mechanism of DOM flocs. The TiCl3 showed a significantly higher capacity for DOC removal at pH around 3 at which charge neutralization was found to be the dominant mechanism for the floc formation. This was further evident from the relatively larger floc sizes obtained with TiCl3 treatment. However, destabilization of Ti-flocs occurred at pH 4.5 through an adsorption-enmeshment mechanism due to a highly negative zeta potential. Additionally, fluorescence spectroscopic analyses showed that TiCl3 was more efficient than alum in removing humic compounds. A two-stage treatment process by alum and TiCl3, either as the same chemical or both showed better performance than a single dose treatment. The results indicate that TiCl3 could be an effective alternative coagulant for the treatment of waters, particularly those of low alkalinity and high DOC concentration and low pH wastewaters for removal of hydrophobic compounds and particulate matter