Prevalence of Cannabis Lifetime Use in Iranian High School and College Students: A Systematic Review, Meta-Analyses,and Meta-Regression

Cannabis is the most widely used substance in the world. This study aimed to estimate the prevalence of cannabis lifetime use (CLU) in high school and college students of Iran and also to determine factors related to changes in prevalence. A systematic review of literature on cannabis use in Iran was conducted according to MOOSE guideline. Domestic scientific databases, PubMed/Medline, ISI Web of Knowledge, and Google Scholar, relevant reference lists, and relevant journals were searched up to April, 2014. Prevalences were calculated using the variance stabilizing double arcsine transformation and confidence intervals (CIs) estimated using the Wilson method. Heterogeneity was assessed by Cochran's Q statistic and I-2 index and causes of heterogeneity were evaluated using meta-regression model. In electronic database search, 4,000 citations were retrieved, producing a total of 33 studies. CLU was reported with a random effects pooled prevalence of 4.0 (95 CI = 3.0 to 5.0). In subgroups of high school and college students, prevalences were 5.0 (95 CI = 3.0 to -7.0) and 2.0 (95 CI = 2.0 to -3.0), respectively. Meta-regression model indicated that prevalence is higher in college students (beta = 0.089, p < .001), male gender (beta = 0.017, p < .001), and is lower in studies with sampling versus census studies (beta = -0.096, p < .001). This study reported that prevalence of CLU in Iranian students are lower than industrialized countries. In addition, gender, level of education, and methods of sampling are highly associated with changes in the prevalence of CLU across provinces

Wavelength-Selective Switch with Direct Few Mode Fiber Integration

The first realization of a wavelength-selective switch (WSS) with direct integration of few mode fibers (FMF) is fully described. The freespace optics FMF-WSS dynamically steers spectral information-bearing beams containing three spatial modes from an input port to one of nine output ports using a phase spatial light modulator. Sources of mode dependent losses (MDL) are identified, analytically analyzed and experimentally confirmed on account of different modal sensitivities to fiber coupling in imperfect imaging and at spectral channel edges due to mode clipping. These performance impacting effects can be reduced by adhering to provided design guidelines, which scale in support of higher spatial mode counts. The effect on data transmission of cascaded passband filtering and MDL build-up is experimentally investigated in detail

Prevalence of Cannabis Lifetime Use in Iranian High School and College Students: A Systematic Review, Meta-Analyses,and Meta-Regression

Cannabis is the most widely used substance in the world. This study aimed to estimate the prevalence of cannabis lifetime use (CLU) in high school and college students of Iran and also to determine factors related to changes in prevalence. A systematic review of literature on cannabis use in Iran was conducted according to MOOSE guideline. Domestic scientific databases, PubMed/Medline, ISI Web of Knowledge, and Google Scholar, relevant reference lists, and relevant journals were searched up to April, 2014. Prevalences were calculated using the variance stabilizing double arcsine transformation and confidence intervals (CIs) estimated using the Wilson method. Heterogeneity was assessed by Cochran's Q statistic and I-2 index and causes of heterogeneity were evaluated using meta-regression model. In electronic database search, 4,000 citations were retrieved, producing a total of 33 studies. CLU was reported with a random effects pooled prevalence of 4.0 (95 CI = 3.0 to 5.0). In subgroups of high school and college students, prevalences were 5.0 (95 CI = 3.0 to -7.0) and 2.0 (95 CI = 2.0 to -3.0), respectively. Meta-regression model indicated that prevalence is higher in college students (beta = 0.089, p < .001), male gender (beta = 0.017, p < .001), and is lower in studies with sampling versus census studies (beta = -0.096, p < .001). This study reported that prevalence of CLU in Iranian students are lower than industrialized countries. In addition, gender, level of education, and methods of sampling are highly associated with changes in the prevalence of CLU across provinces

Automatic Choroid Layer Segmentation from Optical Coherence Tomography Images Using Deep Learning

The choroid layer is a vascular layer in human retina and its main function is to provide oxygen and support to the retina. Various studies have shown that the thickness of the choroid layer is correlated with the diagnosis of several ophthalmic diseases. For example, diabetic macular edema (DME) is a leading cause of vision loss in patients with diabetes. Despite contemporary advances, automatic segmentation of the choroid layer remains a challenging task due to low contrast, inhomogeneous intensity, inconsistent texture and ambiguous boundaries between the choroid and sclera in Optical Coherence Tomography (OCT) images. The majority of currently implemented methods manually or semi-automatically segment out the region of interest. While many fully automatic methods exist in the context of choroid layer segmentation, more effective and accurate automatic methods are required in order to employ these methods in the clinical sector. This paper proposed and implemented an automatic method for choroid layer segmentation in OCT images using deep learning and a series of morphological operations. The aim of this research was to segment out Bruch’s Membrane (BM) and choroid layer to calculate the thickness map. BM was segmented using a series of morphological operations, whereas the choroid layer was segmented using a deep learning approach as more image statistics were required to segment accurately. Several evaluation metrics were used to test and compare the proposed method against other existing methodologies. Experimental results showed that the proposed method greatly reduced the error rate when compared with the other state-of-the art methods

Learning Abstract Concepts of Modern Physics Applied Laser Areas to Help

The focus of this study was to clarify the degree of relationship between field Transfer of Learning by means of application in the modern physics (laser) and common field. To achieve this goal an intact group of 85 students in introductory level college in Shahreray zone in Tehran in Iran participated in test. The major objectives of the test were to investigate students’ transfer of physics learning from their experiences of watching laser applications to the provided physical models, from one model to the other and from the models to the modern physics (laser) problems. To find the degree of relationship between tow variables point- biserial correlation coefficient was used. To compare the mean scores of the tow variables the independent T-test technique was used. The result of the statistical analyses revealed that in the knowledge domain that was significant difference between the control and the experimental groups

Model of Anti-Stokes Cooling in a Yb-Doped Fiber

We use a comprehensive model of cooling by anti-Stokes fluorescence in a single-mode fiber that includes the effects of fiber loss, concentration quenching, mode profiles, and amplified spontaneous emission to analyze the trends of cooling in single-mode Yb-doped ZBLANP fibers. Simulations demonstrate that heat extraction varies significantly along the fiber. There is an optimum pump power (58 mW at 1015 nm for the modeled fiber) for which the maximum heat extracted per unit length is at the start of the fiber. Launching more power moves the coolest point further down the fiber. At substantially higher powers, ASE has a significant heating effect, and coupled with the heating due to absorptive loss, the entire fiber warms up. For a given fiber length, the total extracted heat is maximized for a different pump power (430 mW for a 20-m length). The temperature change is then negative along the entire fiber, and the total extracted heat is 7.12 mW (1.65% cooling efficiency). When the fiber absorptive loss is negligible, this value increases to 30.5 mW for a 2-W pump, giving a 3.48% cooling efficiency, only slightly below the quantum limit (3.7%). The optimum dopant concentration has a similar trade-off: The total extracted heat is maximized for a Yb concentration of 2 wt.%, and the cooling efficiency for 0.5 wt.%. A model of ASF cooling in fiber lasers is also described and exploited to investigate how to select the fiber laser parameters to extract the most power output from a radiation-balanced fiber laser. It shows that increasing the cavity length increases cooling at the expense of laser efficiency, and that a low output coupler reflectivity enhances ASF cooling. Simulations predict that a large-mode-area fiber laser should produce 12.7 W of output power at 63% efficiency, a performance limited by the fiber\u27s absorptive loss, the core diameter (30 µm), and concentration quenching

Model of Anti-Stokes Fluorescence Cooling in a Single-Mode Optical Fiber

We report a comprehensive model that quantifies analytically and numerically the heat that can be extracted by anti-Stokes fluorescence (ASF) from a fiber doped with a quasi-two-level laser ion. This model is used to investigate the effects on cooling of all relevant fiber and pump parameters, as well as amplified spontaneous emission. Simulations of a typical Yb-doped ZBLANP single-mode fiber show that for short enough fibers the heat extraction is relatively uniform along the fiber length. There is an optimum pump wavelength and power that maximizes the heat extracted per unit length. At this power, the coolest point is at the fiber input end. At higher powers, the coolest spot moves further down the fiber. The total heat extracted from a fiber, important for payload cooling, depends on the fiber absorptive loss, the pump wavelength, and the pump power. Simple expressions are derived to predict the optimum dopant concentration that maximizes heat extraction and the maximum tolerable absorptive fiber loss above which cooling is unobtainable. In a fiber with negligible residual absorption, the cooling efficiency is predicted to be 3.7%. In the modeled fiber, it is reduced to 1.7% in part by concentration quenching, but mainly due to the fiber absorptive loss (∼15 dB/km). Since the total extracted heat increases linearly with core radius and dopant concentration (up to a limit determined by concentration quenching), highly doped multimode fibers are strong candidates for payload cooling. This model can be straightforwardly expanded to design and optimize fiber lasers and amplifiers that utilize ASF for cooling