Optimization-Based Economical Flexural Design of Singly Reinforced Concrete Beams: A Parametric Study

In the past, many studies have been conducted on the optimization of reinforced concrete (RC) structures. These studies have demonstrated the effectiveness of different optimization techniques to obtain an economical design. However, the use of optimization techniques to an obtain economical design is not so practical due to the difficulty in applying most of the optimization techniques to achieve an optimal solution. The RC beam is one of the most common structural elements encountered by a practising design engineer. The current study is designed to highlight the potential of the Solver tool in MS Excel as an easy-to-use option for optimizing the design of simply supported RC beams. A user-friendly interface was developed in a spreadsheet in which beam design parameters from a typical design can be entered and an economical design can be obtained using the Evolutionary Algorithm available in the MS Excel Solver tool. To demonstrate the effectiveness of the developed optimization tool, three examples obtained from the literature have been optimized. The results showed that up to 24% economical solution can be obtained by keeping the same material strengths that were assumed in the original design. However, if material strength is also considered as a variable, up to 44% of the economical solution can be obtained. A parametric study was also conducted to investigate the effect of different design variables on the economical design of simply supported RC beams and to derive useful rules of thumb for their design and proportioning, with the objective of cost minimization. The results of the parametric study suggest that the grade of the reinforcing steel is one of the most influential factors that affect the cost of simply supported RC beams. Practicing engineers can use the trends derived from this research to further refine their optimal designs.     

Controlling the Wettability of ZnO Thin Films by Spray Pyrolysis for Photocatalytic Applications

Herein, we synthesized the zinc oxide (ZnO) thin films (TFs) deposited on glass substrates via spray pyrolysis (SP) to prepare self-cleaning glass. Various process parameters were used to optimize photocatalytic performance. Substrates were coated at room temperature (RT) and 250 °C with a 1 mL or 2 mL ZnO solution while maintaining a distance from the spray gun to the substrate of 20 cm or 30 cm. Several characterization techniques, i.e., XRD, SEM, AFM, and UV–Vis were used to determine the structural, morphological, and optical characteristics of the prepared samples. The wettability of the samples was evaluated using contact angle measurements. As ZnO is hydrophilic in nature, the RT deposited samples showed a hydrophilic character, whereas the ZnO TFs deposited at 250 °C demonstrated a hydrophobic character. The XRD results showed a higher degree of crystallinity for samples deposited on heated substrates. Because of this higher crystallinity, the surface energy decreased, and the contact angle increased. Moreover, by using 2 mL solution, better surface coverage and roughness were obtained for the ZnO TFs. However, by exploiting the distance of the spray to the samples size distribution and surface coverage can be controlled, the samples deposited at 30 mL showed a uniform particle size distribution from 30–40 nm. In addition, the photoactivity of the samples was tested by the degradation of rhodamine B dye. Substrates prepared with a 2 mL solution sprayed at 20 cm showed higher dye degradation than other samples, which can play a vital role in self-cleaning. Hence, by changing the said parameters, the ZnO thin film properties on glass substrates were optimized for self-cleaning diversity.     

Fungal Orbital Cellulitis: Presenting Features,Management and Outcomes at a Referral Center

Purpose: To report a series of patients with fungal orbital cellulitis who underwent exenteration surgery and describe presenting features, management and outcomes at a referral center.

Methods: Retrospective case series.

Results: From November 2011 to March 2014, four patients underwent orbital exenteration for fungal orbital cellulitis at the University of Illinois. Three patients had mucormycosis and one had aspergillosis. All patients were treated with intravenous antifungals and underwent orbital exenteration. Two patients were successfully treated with supplemental intra-orbital catheter delivery of amphotericin B. Presenting visual acuity in the affected eye ranged from 20/25 to no light perception. Some level of ophthalmoplegia was present in three patients. Significantly elevated intraocular pressure was found in two patients. All patients with mucormycosis were found to have uncontrolled diabetes mellitus. One patient had a history of myelodysplastic syndrome, chronic hepatitis C infection, polysubstance abuse and Crohn’s disease. Another patient had a history of alcoholic liver cirrhosis, Crohn’s disease treated with systemic immunosuppression and renal cell carcinoma. The patient with aspergillosis had myelodysplastic syndrome and portal hypertension, and the initial presentation resembled giant cell arteritis. Two of four patients died during their hospitalization.

Conclusions: Fungal orbital cellulitis has a high mortality rate despite aggressive antifungal treatment and orbital exenteration performed soon after the diagnosis is confirmed. Patients often have a history of immunosuppression and the onset may be insidious. There must be a high rate of suspicion for fungal orbital cellulitis given the appropriate signs and medical history in order to avoid treatment delay.     

Continuation rates and reasons for discontinuation of intra-uterine device in three provinces of Pakistan: results of a 24-month prospective client follow-up

Background

Long-acting reversible contraceptives, such as the intrauterine device (IUD), remain underutilised in Pakistan with high discontinuation rates. Based on a 24-month prospective client follow-up (nested within a larger quasi-experimental study), this paper presents the comparison of two intervention models, one using private mid-level providers branded as “Suraj” and the other using community midwives (CMWs) of Maternal Newborn and Child Health Programme, for method continuation among IUD users. Moreover, determinants of IUD continuation and the reasons for discontinuation, and switching behaviour were studied within each arm.

Methods

A total of 1,163 IUD users, 824 from Suraj and 339 from the CMW model, were enrolled in this 24-month prospective client follow-up. Participants were followed-up by female community mobilisers physically every second month to ascertain continued IUD usage and to collect information on associated factors, switching behaviour, reasons for discontinuation, and pregnancy occurrence. The probabilities of IUD continuation and the risk factors for discontinuation were estimated by life table analysis and Cox proportional-hazard techniques, respectively.

Results

The cumulative probabilities of IUD continuation at 24 months in Suraj and CMW models were 82% and 80%, respectively. The difference between the two intervention areas was not significant. The probability distributions of IUD continuation were also similar in both interventions (Log rank test: χ² = 0.06, df = 1, P = 0.81; Breslow test: χ² = 0.6, df = 1, P = 0.44). Health concerns (Suraj = 57.1%, CMW = 38.7%) and pregnancy desire (Suraj = 29.3%, CMW = 40.3%) were reported as the most prominent reasons for IUD discontinuation in both intervention arms. IUD discontinuation was significantly associated with place of residence in Suraj and with age (15–25 years) in the CMW model.

Conclusion

CMWs and private providers are equally capable of providing quality IUD services and ensuring higher method continuation. Pakistan’s National Maternal Newborn and Child Health programme should consider training CMWs and providing IUDs through them. Moreover, private sector mid-level providers could be engaged in promoting the use of IUDs.

     

Ventricular fibrillation in a left ventricular assist device patient: Can the echocardiogram be misleading?

Sustained ventricular tachycardia and ventricular fibrillation (VF) are life-threatening arrhythmias which remain highly prevalent in patients with advanced heart failure. These ventricular arrhythmias may impair the support provided by continuous-flow left ventricular assist devices (CF-LVADs) and lead to frequent hospitalizations, antiarrhythmic medication use, external defibrillations, and need for heart transplantation. We report a case in which a patient with a CF-LVAD and an implantable cardioverter defibrillator at end of life presented with asymptomatic low-flow alarms and was found to have VF of unknown duration. Unique in our case was the presence of apparent organized contractility and rhythmic opening of the mitral valve on echocardiogram despite VF on electrocardiogram.     

Effect of obstruction on longitudinal left ventricular shortening in hypertrophic cardiomyopathy.

OBJECTIVES: We investigated the cause of the midsystolic drop (MSD) in left ventricular (LV) ejection velocities that are observed with hypertrophic cardiomyopathy (HCM) and severe obstruction. BACKGROUND: Dynamic obstruction is an important determinant of symptoms and adverse outcome. The MSD in velocity and flow occurs in patients with gradients >60 mm Hg. The nadir velocity in the LV occurs simultaneously with peak gradient. METHODS: We studied 36 patients with obstructive HCM and an MSD and compared them with 15 patients with HCM and no obstruction and with 25 age-matched normal control subjects. We measured LV ejection velocity proximal and distal to LV obstruction as well as tissue Doppler velocities and time intervals. RESULTS: The duration of contraction of both the septum and lateral wall is shorter in obstructed patients with the MSD than in nonobstructed HCM patients: septal contraction 203 +/- 68 ms vs. 271 +/- 41 ms (p < 0.001). Parallel reduction in the length of shortening was noted: 1.2 +/- 0.6 cm vs. 1.9 +/- 0.4 cm (p < 0.001). The ejection velocity nadir follows the septal and lateral peak velocities by 100 ms and 60 ms, respectively. The velocity nadir occurs as both walls rapidly decelerate to their premature termination: septal deceleration 79 +/- 35 cm/s2 vs. 48 +/- 21 cm/s2 (p < 0.001). With medical abolition of obstruction the MSD disappears and the duration and length of contraction normalizes. CONCLUSIONS: These data indicate that the MSD is caused by premature termination of LV segmental shortening and is a manifestation of systolic dysfunction.     

Esophageal Involvement in Lymphoma

Esophageal involvement by lymphoma in three patients, two with non-Hodgkin's lymphoma and one with Hodgkin's lymphoma are reported. In all three patients, there was discrete involvement of the esophagus not directly contiguous with the stomach. Esophageal involvement by lymphoma either as a primary disease or as manifestation of a disseminated disease is distinctly uncommon.