The examining two approaches for facilitating the process of arithmetic word problems solving

This paper focuses on two approaches for facilitating the process of word problems solving. The first approach distinguishes different kinds of occurred errors and the second one recognizes various required and underlying knowledge. The first approach applies Kinfong and Holtan's framework of occurred errors and the second approach applies Mayer’s theory (1992) of underlying knowledge for solving word problems. The main aim of this paper is to examine the relationship between different kinds of occurred errors and various required knowledge in solving Arithmetic word problems. The research methodology is a semi experimental method. The subjects include 89 eight grade students (male and female). The research tools are a descriptive math test regarding six word problems and a directed interview. The results indicate that in solving the arithmetic word problems, increasing students' errors result from lack of linguistic, semantic, structural and communicational knowledge. This study explored that the possible connection between the two approaches for facilitating solving word problems is very important. That is because clarity of this relationship may increase math teachers’ insight about the nature of different kinds of occurred errors and the different aspects of knowledge necessary for solving word problems

The dependence of the hydrogen sorption capacity of single-walled carbon nanotubes on the concentration of catalyst

The adsorption of hydrogen on single-walled carbon nanotubes was measured using micro-gravimetric nitrogen and hydrogen adsorption isotherms at 77 K for gas pressures of up to 1 bar (nitrogen) and 12 bar (hydrogen). Results show that surface area and hydrogen uptake depend on the concentration of the iron catalyst used for making the nanotubes. Langmuir fits to the hydrogen uptake curves clearly show two adsorption energies for each sample which we attribute to the groove site for the higher adsorption energy and to the convex tube surface for the lower energy. We also present calculations of the binding energy of hydrogen on these same sites on SWCNTs and confirm that the groove site has a significantly higher (radius-dependent) binding energy than the surface site, consistent with the experimental values. This suggests that the use of the Langmuir model is appropriate to the adsorption of H2 on activated carbons for the temperature and pressure range investigated and could be used as a rapid way of estimating the average tube radius in the sample

A Novel Multi-Level Cascade Inverter with Reduced Switching Devices to Connect Renewable Energy Sources to the Grid

Multi-level inverters (MLIs) have now become an essential component for medium and high power applications with medium voltage levels. Low switches multi-level inverters are very popular due to their high efficiency, low cost, and easy control for output with higher levels. In this paper, a new multi-level inverter structure based on a switched DC voltage source is proposed by reducing the number of switches for single-phase applications. The proposed structure can be used in grid-connected applications, such as grid connections for renewable energy sources. The proposed structure is developed with a higher number of levels at the output using a smaller number of devices. The proposed topology can also be used in symmetric and asymmetric configurations. Two switching methods including pulse width modulation (PWM) switching and ladder switching based on selective harmonic elimination (SHE) have been used to generate the output voltage. Comparative studies with multilevel inverters were presented recently to show the advantage of the proposed structure in terms of reducing the number of devices. Simulation and experimental results are presented to confirm the performance of the proposed topology. In addition, the performance of the proposed multilevel structure for energy transfer from renewable sources to the low-power grid has also been investigated

Non-surgical Treatments of Esophageal Cancer

    Esophageal cancer is one of the most common malignancies with a growing occurrence. It presently ranks ninth among the most frequent cancers in the world and the sixth leading cause of death from cancer. For a variety of reasons, the mainstream of patients with esophageal cancer is actually not suitable for Esophagectomy. More than 50% have locally advanced unresectable or metastatic tumors at diagnosis. Other reasons which exclude Esophagectomy include old age, comorbidity or refusal by the patient. For more advanced stages of esophageal cancers, the basis of non-surgical treatment is chemotherapy (CT) or radiotherapy (RT), either alone or in combination as chemoradiotherapy (CRT). The purpose of this study is to summaries and judgmentally analyzes current non-surgical treatments. Although the best treatment for locally advanced esophageal cancer is still being debated, the use of neoadjuvant chemoradiotherapy has gained acceptance

Determination of primary electron beam parameters in a Siemens Primus Linac using Monte Carlo simulation

The Monte Carlo method can be used to describe any technique that approximates solutions to quantitative problems through statistical sampling. This method is considered to be the most accurate method for dose calculation in radiotherapy. For complete modeling of a linear accelerator, it is required that the manufactured information covers all data, but some data such as primary electron energy must be indicated. The purpose of this study was to determine the best primary electron energy for 15 MV photon beam with varying the energy and FWHM. A Monte Carlo model for photon-beam output of a Siemens primus linear accelerator was validated by plotting the energy spectrum of photon beam and calculating the percentage depth dose (PDD) and beam profiles for 10×10 cm2 field. Square 10×10 cm2 field was validated by measurements in water by a farmer chamber. Linac head simulation was performed with BEAMnrc and dose calculation and 3D dose file were produced by DOSXYZnrc. The results were analyzed using MATLAB. It was found a good agreement between calculated PDD and beam profile for 15 MV photon beam using Monte Carlo simulation with primary electron energy of 11 MV and FWHM of 0.4 with maximum dose difference of 1.2% in PDD curves. In conclusion, using primary electron energy of 11 MV and FWHM of 0.4 has very good accuracy in calculating of dose distribution for 15 MV photon beam and it can be considered as a promising method for patient dose calculations

Pharmacogenetics of anticancer drug sensitivity and toxicity in colorectal cancer

Inter-individual differences in drug response are an important cause of failure in anticancer treatment and adverse drug events in cancer patients. Gene polymorphisms related to these outcomes have been investigated in an effort to find new genetic biomarkers to predict toxicity and response to anticancer drugs. Evaluating the value single nucleotide polymorphisms (SNPs) in the genes involved in transportation, activation and metabolism of anticancer drugs provides a promising approach to select the appropriate therapeutic regimes with at least adverse reactions. This review summarizes the current knowledge about the relationship between of SNPs involved in the transportation, activation and metabolism of anticancer drugs and treatment outcomes in colorectal cancer (CRC) patients

Study of Pluto's Atmosphere Based on 2020 Stellar Occultation Light Curve Results

On 6 Jun 2020, Pluto's stellar occultation was successfully observed at a ground-based observatory and Pluto's atmospheric parameters were investigated. We used an atmospheric model of Pluto (DO15), assuming a spherical and transparent pure N2 atmosphere. Using ray-tracing code the stellar occultation light curve was satisfactorily fitted to this model. We found that Pluto's atmospheric pressure at the reference radius of 1215 km is 6.72+_0.21 {\mu}bar. Our estimated pressure shows a continuation of the increasing pressure studied in 2016 consistent with a seasonal volatile transport model. We concluded that the N2 condensation processes in the Sputnik Planitia glacier are increasing due to the heating of the N2 ice in this basin. This study's result was shown on the diagram of the annual evolution of atmospheric pressure.Comment: 4 figures, 2 table

MnCo2O4/NiCo2O4/rGO as a Catalyst Based on Binary Transition Metal Oxide for the Methanol Oxidation Reaction

The demands for alternative energy have led researchers to find effective electrocatalysts in fuel cells and increase the efficiency of existing materials. This study presents new nanocatalysts based on two binary transition metal oxides (BTMOs) and their hybrid with reduced graphene oxide for methanol oxidation. Characterization of the introduced three-component composite, including cobalt manganese oxide (MnCo2O4), nickel cobalt oxide (NiCo2O4), and reduced graphene oxide (rGO) in the form of MnCo2O4/NiCo2O4/rGO (MNR), was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray (EDX) analyses. The alcohol oxidation capability of MnCo2O4/NiCo2O4 (MN) and MNR was evaluated in the methanol oxidation reaction (MOR) process. The crucial role of rGO in improving the electrocatalytic properties of catalysts stems from its large active surface area and high electrical conductivity. The alcohol oxidation tests of MN and MNR showed an adequate ability to oxidize methanol. The better performance of MNR was due to the synergistic effect of MnCo2O4/NiCo2O4 and rGO. MN and MNR nanocatalysts, with a maximum current density of 14.58 and 24.76 mA/cm2 and overvoltage of 0.6 and 0.58 V, as well as cyclic stability of 98.3% and 99.7% (at optimal methanol concentration/scan rate of 20 mV/S), respectively, can be promising and inexpensive options in the field of efficient nanocatalysts for use in methanol fuel cell anodes

The potential prognostic and therapeutic application of tissue and circulating microRNAs in cervical cancer

Cervical cancer (CC) is a common malignancy in women and a major cause of cancer- related mortality globally. Some novel biomarkers may enable the early diagnosis and monitoring of CC. MicroRNAs are small noncoding RNAs that control gene translation at a post transcriptional level. Hence the deregulation of these molecules can cause many diseases. There appears to be an association between aberrant miRNA expression and CC, but the molecular mechanisms involved in the development of CC remain unknown. The upregulation of some circulating miRNAs, e.g. miRNA-20a, miRNA-203, miRNA-21, miRNA-205, miRNA-218, and miR-485-5, as well as tissue specific-miRNAs, e.g. miR-7, miR-10a, miR-17-5p, miR-135b, miR-149 and miR-203 has been found in patients with CC. There is also growing evidence for the importance of miRNAs in the development of drug-resistance. This review therefore highlights recently published preclinical and clinical investigation performed on tissue-specific and circulating miRNAs, as potential biomarkers for the detection of patients at early stages of CC, in the prediction of prognosis, and monitoring of their response to therapy. Key word: cervical cancer, CIN, MiRNA, circulating biomarker, tissue-specific biomarker, HP

Epigenetic drug therapy in the treatment of colorectal cancer

Colorectal cancer (CRC) is one of the most common cancers with a high rate of morbidity and mortality worldwide. The incidence of CRC is similar in men and women but is distributed uniformly globally. It has been demonstrated that epigenetic alterations which may cause changes in the expression of microRNA, DNA methylation and histone acetylation that results in inheritable modifications in gene expression in colorectal epithelial cells, plays a crucial role in the development of CRC. Recently, targeting epigenetic modification has emerged as a potentially important treatment approach in CRC. The US Food and Drug Association has approved the use of some epigenetic drugs that may be able to inhibit or reverse these alterations and also enhance sensitivity to chemotherapeutic agents and radiotherapy in CRC. In this review we have summarized the recent pre-clinical and clinical trial studies investigating the therapeutic value of using epigenetic drugs as novel therapeutic approach in CRC treatment. Keywords: epigenetic, colorectal cancer, drug, DNA methylation, histone acetylatio