CFD simulation of convective heat transfer in vessel with mechanical agitation for milk

Computational fluid dynamics (CFD) analysis using ANSYS Fluent software has been carried out to investigate velocity profiles and thermal characteristics of milk during heating under mechanically agitated condition. In earlier article experimental data on forced convection heat transfer coefficient h - and correlations of the form N u = a · R e b · P r 0.33 for cow milk, standardised milk and full cream milk in Baffled vessel and Unbaffled vessel with scraping, using Propeller, Flat Six Blade Turbine (FBT), Inclined Six Blade Turbine (IBT) and Paddle impellers were reported. It was noted milk in Baffled vessel with Paddle impeller provided highest h - even at lower rotational speeds followed by Propeller, FBT and IBT impellers. In Unbaffled vessel with scraping, Propeller provided the highest h - followed by FBT and IBT impellers. Hence, the present investigation has been carried out to validate and understand how different velocity of flow currents and their magnitude influence the heat transfer coefficient values in CFD simulation. It also justifies the relative performance of the impellers delineated in the earlier paper. In addition, theoretical values of heat transfer coefficients computed using CFD shows close agreement with experimental values.

Determination of forced convection heat transfer coefficients and development of empirical correlations for milk in vessel with mechanical agitators

Heating of milk is an important unit operation to produce many milk based products. This process is done either in heat exchangers or in agitated vessels, where the mode and type of heat transfer plays a significant role. Use of mechanical agitator with suitable impeller would result in uniform agitation of the liquid. Data for forced convection heat transfer coefficients for milk in agitated vessel have not been documented. In the present investigation, forced convection heat transfer coefficients for milk, using mechanical agitators in vessels have been determined. Experiments have been conducted in vessels (Baffled as well as Unbaffled vessel) that were designed and fabricated under standard procedure employing: (1) Flat Six Blade Turbine impeller, (2) Inclined Six Blade Turbine impeller, (3) Three Blade Propeller impeller and (4) Two Bladed Paddle. Heat transfer coefficients were determined for h¯ for cow milk (3.5% fat), standardised milk (4.5% fat) and full cream milk (6.0% fat). The Two Bladed Paddle was found to as yield the highest heat transfer coefficient h¯ for all three types of milk. In addition, empirical correlations for the forced convection heat transfer using Nu=a·Reb·Pr0.33 have been developed for each case. These heat transfer correlations derived will find application in large scale design and the experimental setup would be useful for future investigation with different liquids and impellers.

Fulminant myocarditis owing to high-dose interleukin-2 therapy for metastatic melanoma

High-dose interleukin-2 (IL-2) therapy may cause acute myocarditis characterised by diffuse myocardial involvement and occasionally fulminant heart failure. Cardiac MRI (CMRI) provides a comprehensive assessment of myocardial function, inflammation and injury in a single examination and has shown value in the diagnosis of myocarditis. We report a case of a 54-year-old male with metastatic melanoma who developed acute severe myocarditis with fulminant heart failure after high-dose IL-2 therapy. CMRI using a combination of T(2) weighted imaging and T(1) weighted late post-gadolinium enhancement techniques played a key role in establishing the diagnosis. To our knowledge we present the first case report of the combined use of T(1) and T(2) weighted CMRI techniques to diagnose IL-2 induced myocarditis.

An unusual case of acute angle closure glaucoma following argon laser pan retinal photocoagulation

Acute angle closure glaucoma (AACG) is a painful, potentially blinding condition with patients frequently presenting within hours of onset with ocular pain, nausea and vomiting. Argon laser pan-retinal photocoagulation (PRP) is one of the commonest ophthalmic outpatient procedures. It is used in the treatment of vascular disorders of the retina; most commonly diabetic retinopathy. AACG following PRP is a recognised, but rarely occurring, complication. Prompt treatment alleviates pain and improves visual prognosis. The authors report a case of AACG following PRP treatment which was initially mistaken for a viral illness.

Acute dacryoadenitis in Crohn's disease

A 48-year-old Filipino female presented with unilateral acute onset painful red eye, blurred vision and yellow discharge. On examination she had a corrected visual acuity of 6/5 in the right eye and 6/18 in the left eye. There was a left-sided periorbital swelling, with chemosis involving the bulbar conjunctiva on the temporal aspect. Ocular motility showed limitation of left-sided abduction with mild limitation of laevoelevation and laevodepression. She was afebrile and systemic examination was unremarkable. Medical history included diagnosis of Crohn's disease since the age of 20. She was on oral mesalamine 1 g for mildly active colitis. Full blood count was normal but erythrocyte sedimentation rate and C reactive protein were raised. Blood culture and conjunctival swab were negative. Contrast-enhanced CT scan demonstrated enlargement of the lacrimal gland. She was managed conservatively with acetaminophen and codeine for pain and swelling. She recovered completely in 2 weeks with no sequelae.

Intermittent hypoxia suppresses adiponectin secretion by adipocytes

Obstructive sleep apnea (OSA), characterized by cyclic intermittent hypoxia (IH) during sleep, is an independent risk factor for cardiovascular disease. Adiponectin (APN), an adipocytokine secreted exclusively by adipocytes, possesses antiatherogenic properties. Low levels of APN, particularly the high-molecular-weight (HMW) form, are associated with an increased risk of cardiovascular disease. Here, we hypothesized that IH would result in the dysregulation of APN expression and secretion. 3T3-L1 adipocytes were exposed to IH at 12 cycles/h for 6 h/d to simulate the IH condition similar to that encountered in OSA. Control adipocytes were exposed to 21% O(2) under identical conditions. After 48 h of incubation, IH caused a decrease in the secretion of total and HMW APN in spite of a significant upregulation of APN mRNA expression by adipocytes. This study suggested a novel mechanism of how the cyclic hypoxemia in OSA predisposes OSA patients to cardiovascular disease through the dysregulation of secretion of APN by adipocytes. Further studies are needed to determine the exact molecular mechanism how IH reduces the release of APN by adipocytes.

Magnetic resonance imaging of right ventricular morphology and function in boxer dogs with arrhythmogenic right ventricular cardiomyopathy

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a myocardial disease characterized by fibrofatty replacement of the right ventricle and ventricular tachyarrhythmias, reported most commonly in the Boxer dog. Although ARVC is characterized as a myocardial disease, the impact of the disease on the function of the right ventricle has not been well studied.

OBJECTIVE

To noninvasively evaluate the function and anatomy of the right ventricle in Boxer dogs with ARVC.

ANIMALS

Five adult Boxer dogs with ARVC and 5 healthy size-matched hound dogs.

METHODS

Magnetic resonance imaging was performed on an ECG-gated conventional 1.5-T scanner using dark blood imaging and cine acquisitions. Images were evaluated by delineation of endocardial right and left ventricular contours in the end-diastolic and end-systolic phases of each slice. Right and left end-systolic and end-diastolic volumes were generated using Simpson's rule and ejection fraction was calculated. Images were evaluated for right ventricular (RV) aneurysms and wall motion abnormalities. Spin echo images were reviewed for the presence of RV myocardial fatty replacement or scar.

RESULTS

RV ejection fraction was significantly lower in Boxers with ARVC compared with the controls (ARVC 34%+/- 11 control 53%+/- 10, P < .01). There was an RV aneurysm in 1 dog with ARVC but not in any of the controls. RV myocardial gross fatty changes were not observed in dogs of either group.

CONCLUSIONS AND CLINICAL IMPORTANCE

These findings could be interpreted to suggest that arrhythmias and myocardial dysfunction precede the development of morphological abnormalities in dogs with ARVC.

Comparison of 4% articaine and 0.5% levobupivacaine/2% lidocaine mixture for sub-Tenon's anaesthesia in phacoemulsification cataract surgery: a randomised controlled trial

BACKGROUND/AIMS

[corrected] The aim of this study was to compare the efficacy and safety of 4% articaine with a mixture containing equal volumes of 2% lidocaine and 0.5% levobupivacaine without hyaluronidase for sub-Tenon's anaesthesia in phacoemulsification cataract surgery.

METHODS

The study was a prospective, randomised double-masked clinical trial of 65 patients allocated to receive either 4% articaine or a mixture containing equal parts of 2% lidocaine and 0.5% levobupivacaine. All patients had pre- and postoperative Hess charting to document ocular motility dysfunction. Ocular and eyelid movements were scored at 2 min intervals from 2 to 10 min after injection of the anaesthetic agent, and at the end of surgery. Complications related to injection, including pain, chemosis and subconjunctival haemorrhage, were recorded. Patients rated pain (none/mild/moderate/severe) during surgery. The operating surgeon masked to the anaesthetic agent assessed proptosis/chemosis at the start of the operation and the degree of ocular akinesia and analgesia at the end of surgery.

RESULTS

The articaine group demonstrated a rapid onset of ocular akinesia with a mean time to readiness for surgery (achieving a score of </=5) of 4.0 min compared with 10 min for the lidocaine/levobupivacaine group (p = 0.001). The effectiveness of block was significantly greater in the articaine group at all points (p<0.01). Surgeons rated ocular akinesia to be superior in the articaine group (p<0.001). Patients and surgeons rated the analgesic effect as comparable in either group. Eyelid scores, subconjunctival haemorrhage and chemosis were comparable in either group. Hess chart was performed on all patients pre- and postoperatively. There was no clinically significant motility disturbance in the articaine group, whereas one patient in the lidocaine/levobupivacaine group developed diplopia with abnormal ocular motility on the Hess chart.

CONCLUSION

Articaine (4%) is a safer and a superior anaesthetic agent than a mixture of 2% lidocaine and 0.5% levobupicaine in achieving ocular akinesia for sub-Tenon's block in phacoemulsification cataract surgery.

Mydriasis due to Datura inoxia

Unilateral, dilated unresponsive pupil may be secondary to a wide range of ocular and neurological disorders. "Gardener's pupil" is a pharmacological mydriasis caused by exposure to plants containing alkaloids. We report a case of mydriasis related to Datura inoxia, and detail a number of plants that have toxic effects. This report emphasises the importance of accurate history taking when evaluating fixed dilated pupil. We recommend that labelling of such poisonous plants should detail the local and systemic effects of accidental exposure, rather than merely the fact that they are poisonous.

Tricuspid Valvular Regurgitation

Precision in diagnosis always precedes rational therapy. Categorizing tricuspid valvular regurgitation (TVR) as simply organic versus functional limits one's understanding of the complexity of the lesion, and may lead to inadequate therapy. Rather, treatment of TVR should begin with an assessment of the affected components of the tricuspid valve complex (TVC). From this assessment, one constructs an appropriate medical or surgical strategy that seeks to reduce symptoms, restore right heart function, and alter the course of the underlying disease process.

Tissue boundary refinement in magnetic resonance images using contour-based scale space matching

An algorithm for computationally focusing the tissue boundaries detected from magnetic resonance images is presented. The proposed approach is a novel, whole-contour-based technique for tracing edges selected at a coarse scale into successively finer scales to recover the needed precision. The tracing algorithm builds consensus through a fast pixel voting scheme. Also presented is a rigorous method for determining the appropriate itinerary when traversing scale space, beginning from the premise of a maximum pixel migration per unit change in scale parameter. This leads to an efficient method of processing images so as to maximize accuracy and minimize noise. Although the LoG (Laplacian of Gaussian) is used for many of the experiments, results using a novel edge detector which is mathematically superior to and faster to compute than the LoG and for which fewer steps are required to traverse the same effective span in scale space are presented. Experimental results on real data are presented, and other potential applications are discussed.

Should obese patients not undergo coronary artery surgery?

To assess the effect of obesity on the patient's recovery from coronary artery bypass surgery, a prospective study was performed on 200 patients. Group 1 comprised 101 nonobese patients and group 2, 99 obese patients. The mean percentage over the ideal weight was 8.2% in group 1 and 33.4% in group 2 (p less than 0.001). Preoperative assessment revealed no difference in age, sex, height, incidence of diabetes, family history or smoking habits between the two groups. Group 2 had a higher incidence of hypertension (p less than 0.01) and hyperlipidemia (p less than 0.02). The average number of grafts placed per patient was 3.4 +/- 0.8 in group 1 and 3.5 +/- 0.08 in group 2. Operative mortality was 2.9% and 2.0% in groups 1 and 2 respectively. Obesity was a predictive factor in postoperative hypertension (p less than 0.025), in the development of wound infection (p less than 0.01) and in an increased requirement of bronchodilators (p less than 0.01). The postoperative progression of physical activity and length of hospital stay was similar, being 10.9 +/- 5.8 days and 9.7 +/- 9.5 days in groups 1 and 2 respectively. The authors conclude that bypass grafting is an acceptable therapeutic option for obese patients with coronary artery disease.