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Search Results: 1 - 10 of 462138 matches for " A. Khosravi "
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Design of 1.33 μm and 1.55 μm Wavelengths Quantum Cascade Photodetector  [PDF]
S. Khosravi, A. Rostami
Optics and Photonics Journal (OPJ) , 2017, DOI: 10.4236/opj.2017.78B016
Abstract:
In this paper, a quantum cascade photodetector based on intersubband transitions in quantum wells with ability of detecting 1.33 μm and 1.55 μm wavelengths in two individual current paths is introduced. Multi quantum wells structures based on III-Nitride materials due to their large band gaps are used. In order to calculate the photodetector parameters, wave functions and energy levels are obtained by solving 1-D Schrodinger–Poisson equation self consistently at 80 ?K. Responsivity values are about 22 mA/W and 18.75 mA/W for detecting of 1.33 μm and 1.55 μm wavelengths, respectively. Detectivity values are calculated as 1.17 × 107 (Jones) and 2.41 × 107 (Jones) at wavelengths of 1.33 μm and 1.55 μm wavelengths, respectively.
Needlestick Injuries among Nurses
H Ebrahimi,A Khosravi
Journal of Research in Health Sciences , 2011,
Abstract: Background: Needlestick injuries (NSIs) are among the most important occupational injuries for health care workers (HCWs). In Iran, the problem of exposure to contaminated blood among nursing personnels has not well documented. The aim of this study was to determine the incidence of needlestick injuries in population of nurses in Shahroud Imam Hossein Hospital, northern Iran. Methods: A self-administrated questionnaire was completed by 180 nurses in September and October 2005 for their NSIs experience in the past year. In this study, needlestick injury was defined as percutaneous injury caused by hollow-borne needles, suturing needles, scalpel blades and lancets. Results: The case incidence of NSIs was 63.3% (114/180). The total number of episodes of NSIs among respondents was 220 (range: 1-5 episodes) with incidence rate of episodes i.e. 1.2 per person/year. 12.8% of nurses had not been vaccinated against hepatitis B virus (HBV). The causal devices in 105 cases (92.1%) were hollow-borne needles and the main causes of percutaneous injuries with hollow-bore needles were recapping (32.4%) and manipulating needles in patients (18.1%). The majority (51.8%) of injuries occurred after use and before disposal of the objects.
When right n-Engel elements of a group form a subgroup?
A. Abdollahi,H. Khosravi
Mathematics , 2009,
Abstract: Let $R_n(G)$ denotes the set of all right $n$-Engel elements of a group $G$. We show that in any group $G$ whose 5th term of lower central series has no element of order 2, $R_3(G)$ is a subgroup. Furthermore we prove that $R_4(G)$ is a subgroup for locally nilpotent groups $G$ without elements of orders 2, 3 or 5; and in this case the normal closure $^G$ is nilpotent of class at most 7 for each $x\in R_4(G)$. Using a group constructed by Newman and Nickel we also show that, for each $n\geq 5$, there exists a nilpotent group of class $n+2$ containing a right $n$-Engel element $x$ and an element $a\in G$ such that both $[x^{-1},_n a]$ and $[x^{k},_n a]$ are of infinite order for all integers $k\geq 2$. We finish the paper by proving that at least one of the following happens: (1) There is an infinite finitely generated $k$-Engel group of exponent $n$ for some positive integer $k$ and some 2-power number $n$. (2) There is a group generated by finitely many bounded left Engel elements which is not an Engel group.
On the right and left 4-Engel elements
A. Abdollahi,H. Khosravi
Mathematics , 2009,
Abstract: In this paper we study left and right 4-Engel elements of a group. In particular, we prove that $$ is nilpotent of class at most 4, whenever $a$ is any element and $b^{\pm 1}$ are right 4-Engel elements or $a^{\pm 1}$ are left 4-Engel elements and $b$ is an arbitrary element of $G$. Furthermore we prove that for any prime $p$ and any element $a$ of finite $p$-power order in a group $G$ such that $a^{\pm 1}\in L_4(G)$, $a^4$, if $p=2$, and $a^p$, if $p$ is an odd prime number, is in the Baer radical of $G$.
Right 4-Engel elements of a group
A. Abdollahi,H. Khosravi
Mathematics , 2010,
Abstract: We prove that the set of right 4-Engel elements of a group $G$ is a subgroup for locally nilpotent groups $G$ without elements of orders 2, 3 or 5; and in this case the normal closure $^G$ is nilpotent of class at most 7 for each right 4-Engel elements $x$ of $G$.
Comparison of Plasma Leptin Levels in Patients with Normal, Low and High Risk Myocardial Perfusion Scan1
A. Bagheri,R. Olamaei,A. Khosravi,M. Khosravi
Iranian Journal of Nuclear Medicine , 2006,
Abstract: Introduction: Leptin, secreted from adipose tissue may have some correlation with coronary artery disease according to some reports in literature. The mean concentration of plasma leptin in patients with normal and abnormal myocardial perfusion imaging (MPI) and relation of leptin levels, independently to abnormality in MPI after correction for body mass index (BMI) was evaluated. Methods: As a cross-sectional study on 270 patients (July-December 2004), data was collected by questionnaire, history and physical examination. After a 12-hours overnight fast, blood samples were obtained. Myocardial perfusion scan was performed and quantitative assessment according to 17 segments analysis was carried out. Results: For 114(42.2%) males and 156(57.8%) females, mean age was 55.8±0.7. Frequency of normal, low and high-risk scans were 101 (37.4%), 67 (24.8%), and 102(37.8%), respectively. Close relationship between BMI and leptin levels was observed (r = 0.42). One-way ANOVA for BMI, leptin, triglyceride, total cholesterol, LDL-C, HDL-C and fasting blood sugar didn't show differences between three groups(p>0.05). Adjusted odds ratio of leptin for BMI in presence of abnormal MPI was 1.05 (0.95, CI: 0.82-1.4). Conclusion: Serum leptin level shows no correlation with coronary artery disease risk category or factors (excluding BMI).
Optimal Node Scheduling for Desired Percentage of Coverage in Wireless Sensor Networks  [PDF]
Hamid Khosravi
Wireless Sensor Network (WSN) , 2012, DOI: 10.4236/wsn.2012.45018
Abstract: Recent developments in wireless communication and embedded computing technologies have led to the advent of wireless sensor network technology. Hundreds of thousands of these micro sensors can be deployed in many areas including health, environment and battlefield in order to monitor the domain with desired level of accuracy. When wireless sensors are deployed in an area, the lifetime of the network should last as long as possible according to the original amount of energy. Therefore, reducing energy consumption in WSNs is of primary concern. We have proposed a node scheduling solution that solves the coverage and connectivity problem in sensor networks in an integrated manner. In this way we will divide network life time to finite number of rounds and in each round we will generate a coverage bitmap of sensors of the domain and based on this bitmap it will decided which sensors remain active or go to sleep. We will check the connection of the sensor network by using Laplacian of adjancy graph of active nodes in each round. Also the network will be capable of producing desired percentage of coverage by using coverage bitmap. We will define the connected coverage problem as an optimization problem and we will seek a solution for the problem by using Genetic Algorithm optimization method.
A new hybrid of evolutionary and conventional optimization algorithms
A. Khosravi,A. Lari,J. Addeh
Applied Mathematical Sciences , 2012,
Abstract:
Sarcoma histiocítico: caso clínico y revisión de la literatura
Khosravi Shahi,P.; Castillo Rueda,A. del;
Anales de Medicina Interna , 2005, DOI: 10.4321/S0212-71992005000400007
Abstract: histiocytic sarcoma is a rare neoplasm, and its aetiology is unknown. it is a malignant proliferation of neoplastic cells showing immunophenotypic and morphologic features similar to tissue histiocytes. the clinical course of histiocytic sarcoma is usually agressive. the signs and symptoms of histiocytic sarcoma are systemic symptoms (fever, weight loss), hepatosplenomegaly, adenopathies, intestinal obstruction, rash and pancytopenia. we present the case of a 75 years old woman, with fever, wieght loss, anorexia, fatigue, splenomegaly and pancytopenia. bone marrow examination showed the diagnosis of histiocytic sarcoma.
Exertional abdominal pain as a symptom of secondary pulmonary hypertension in mitral stenosis
J Najafian, N Toghianifar, A Khosravi
Nigerian Journal of Clinical Practice , 2013,
Abstract: We report a rare presentation of mitral stenosis (MS). MS is a common valvular disease, the first manifestation of which is usually easy fatigability and exertional dyspnea. As the disease progresses in severity, other signs and symptoms appear, such as orthopnea, hemoptysis, and peripheral edema. This is the first report of a case of mitral stenosis presenting with exertional abdominal pain as the first manifestation. This case report describes the clinical characteristics of a 55-year-old woman with mitral stenosis and severe pulmonary hypertension, whose first symptom was exertional abdominal pain.
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