Risk minimization and portfolio diversification

We consider the problem of minimizing capital at risk in the Black-Scholes setting. The portfolio problem is studied given the possibility that a correlation constraint between the portfolio and a financial index is imposed. The optimal portfolio is obtained in closed form. The effects of the correlation constraint are explored; it turns out that this portfolio constraint leads to a more diversified portfolio

Application of Queuing Analytic Theory to Decrease Waiting Times in Emergency Department: Does it Make Sense?

Background: Patients who receive care in an emergency department (ED), are usually unattended while waiting in queues. Objectives: This study was done to determine, whether the application of queuing theory analysis might shorten the waiting times of patients admitted to emergency wards. Patients and Methods: This was an operational study to use queuing theory analysis in the ED. In the first phase, a field study was conducted to delineate the performance of the ED and enter the data obtained into simulator software. In the second phase, "ARENA" software was used for modeling, analysis, creating a simulation and improving the movement of patients in the ED. Validity of the model was confirmed through comparison of the results with the real data using the same instrument. The third phase of the study concerned modeling in order to assess the effect of various operational strategies, on the queue waiting time of patients who were receiving care in the ED. Results: In the first phase, it was shown that 47.7% of the 3000 patient records were cases referred for trauma treatment, and the remaining 52.3% were referred for non-trauma services. A total of 56% of the cases were male and 44% female. Maximum input was 4.5 patients per hour and the minimum input was 0.5 per hour. The average length of stay for patients in the trauma section was three hours, while for the non-trauma section it was four hours. In the second phase, modeling was tested with common scenarios. In the third phase, the scenario with the addition of one or more senior emergency resident(s) on each shift resulted in a decreased length of stay from 4 to 3.75 hours. Moreover, the addition of one bed to the Intensive Care Unit (ICU) and/or Critical Care Unit (CCU) in the study hospital, reduced the occupancy rate of the nursing service from 76% to 67%. By adding another clerk to take electrocardiograms (ECG) in the ED, the average time from a request to performing the procedure is reduced from 26 to 18 minutes. Furthermore, the addition of 50% more staff to the laboratory and specialist consultations led to a 90 minute reduction in the length of stay. It was also shown that earlier consultations had no effect on the length of stay. Conclusions: Application of queuing theory analysis can improve movement and reduce the waiting times of patients in bottlenecks within the ED throughput

Biodiversity of isolated cyanobacteria from desert soils in Iran

Cyanobacteria are among the most ubiquitous, ecologically important photo-autotrophs on the Earth. They play important roles in terrestrial environments, especially in arid and semi-arid regions. In this study, the morphological and genetic diversity of the cyanobacteria inhabiting desert soil in Iran were investigated for the first time. The samples were collected at 40 different sites in the Kavir National Park. After cultivation and morphological identification, the 16S rRNA gene was sequenced from the cyanobacterial cultures. Twenty-seven different isolates were genetically and morphologically identified in 23 sites. Morphotypes fitted the description of five genera Phormidium, Trichocoleus, Leptolyngbya, Microcoleus and Tychonema with an abundance of 44.45, 37.04, 11.11, 3.7 and 3.7%, respectively. Sequence comparisons of samples in the National Center for Biotechnology Information (NCBI) and morphological data showed that 48et and 50et strains had 94% similarity to P. animale and 97% similarity to Microcoleus sp., respectively. These strains formed a separate and longer branch in the phylogenetic tree, suggesting relatively distant phylogenetic relationships with other sequences in this study. It seems that these sequences are new strains and other markers are needed for further investigation. Soil analysis showed salinity ranged from 0.23 to 87.8 dS/m and the genus that showed the highest salinity tolerance was Phormidium. The presence of cyanobacterial strains in the Kavir National Park showed that despite the harsh conditions, this place is biologically active

Prevalence of Helicobacter pylori vacA, cagA, cagE, iceA, babA2, and oipA genotypes in patients with upper gastrointestinal diseases

Background and Objectives: Helicobacter pylori has been strongly associated with peptic ulcer diseases, chronic gastritis, ulcers, and reported as a risk factor for gastric cancer, too. The vaculating cytotoxin (vacA), the cytotoxin associated genes (cagA), the induced by contact with epithelium factor antigen (iceA gene), blood adhesion binding antigen (babA2), and outer membrane protein oipA have been described as different virulence factors of H. pylori. The aim of this study was to investigate the prevalence of the vacA, cagA, cagE, iceA, babA2 and oipA genotypes of H. pylori isolates from patients with upper gasterointestinal problem or dyspepsia. Material and Methods: H. pylori isolated from endoscopic biopsies obtained from 222 studied patients. PCR was done only on cultured positive samples. The vacA alleles, cagA, cagE, iceA, babA2 and oipA genotypes were determined by PCR. Results: The isolation rate of H. pylori strains from culture of gastric biopsies was 16.7. The vacA alleles s1, s2, m1 and m2 were detected in 20 (54.1), 14 (37.8), 9 (24.3) and 23 (62.2) isolates, respectively. VacA s1c genotype was detected in 70.3 of isolates. s1m2 was the most frequent vacA allelic combination in the examined H. pylori strains. The cagA gene was detected in 62.2, cagE in 40.5, iceA1 in 48.6, iceA2 in 16.2, oipA in 81.1 (95 CI: 0.0902-0.1798) and babA2 in 94.6 (95 CI: 0.113- 0.207). A significant correlation was observed between vacAs1 and cagA genotypes (P < 0.008), vacAs1/cagE (P = 0.001), vacAs2/cagA (P < 0.047), and vacAs2/cagE (P = 0.016) with Non-ulcer dyspepsia; but there were not observed any correlation between other virulence markers. Conclusion: No significant correlation was found between the existence of vacA, cagA, cagE, iceA, babA2, and oipA genes with peptic ulcer diseases and non-ulcer dyspepsia groups of studied patients

The effect of tamoxifen on the growth of Leishmania major promastigotes and amastigotes in vitro

Background: Treatment of cutaneous leishmaniasis with pentavalent antimony compounds, as an established drug, may have limitations, side effects and recurrence risk. For this reason, finding new and effective drugs is of great importance. In the present study, the effect of tamoxifen on the growth of Leishmania major promastigotes and amastigotes was evaluated in vitro. Materials and Methods: In this experimental study, the effect of different concentrations (1, 5, 10, 20 and 50 μg/ml) of tamoxifen on Leishmania promastigotes and amastigotes were evaluated in three different times (24, 48 and 72h) and the inhibitory concentration 50 (IC50) was calculated by counting of the parasites. The MTT (3-4, 5-dimethylthiazol-2-yl-2, 5 biphenyltetrazolium bromide) assay was used to determine the percentage of live promastigotes and amastigotes after adding tamoxifen. Results: The number of promastigotes and amastigotes were declined in the presence of various concentrations of tamoxifen after 24, 48 and 72 hours of culturing. Twenty-four hours after culturing, the number of parasites was 1.07�106 per ml in the control group and the parasite numbers in the concentrations of 1 and 50 μg/ml tamoxifen were 0.95�106 and 0.06�106, respectively. The IC50 value of tamoxifen was 2.64μg/ml. Conclusion: Tamoxifen has antileishmanial effects in vitro thus, more researches on the effect of tamoxifen in animal models are suggested