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La Ricerca scientifica. 2. ser., pt. 2: Rendiconti. Sezione B: Biologica最新文献

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A year of online classes amid COVID-19 pandemic at a Bangladeshi university: Economics students’ experience and suggestions for improvements 2019冠状病毒病大流行期间,孟加拉国一所大学一年的在线课程:经济学学生的经验和改进建议
Pub Date : 2021-07-26 DOI: 10.37074/jalt.2021.4.2.3
M. Shuchi, S. Tabassum, Mmk Toufique
Current works perusing online learning amid the COVID-19 pandemic have several drawbacks, i.e., non-representative sample, closed-ended questions, and ignoring students’ opinions about improvement. Also, most studies were carried out in the first weeks of online classes, and no study focused on university-level economics students. This paper uses a convenience sampling technique and open-ended questions and collects data from 154 university-level economics students who have participated in online learning for a year. According to the findings, advantages of online classes include that students can do classes from home avoiding health risks, easy accessibility, flexibility, cost-saving, reducing the likelihood of semester loss, and learning new technologies. Major disadvantages are network problems, difficulties in understanding the topic, unsuitability for mathematical courses, concentration problems, non-interactive classes, financial constraints, adverse health impacts, device and internet problems. Disadvantages outnumbered advantages. Students made several suggestions: using state-of-the-art digital tools, recording and uploading lectures, resolving internet and network issues, holding classes that comply with a fixed schedule, greater efforts to make the topics easier, reducing class duration, institutional support, and introducing an online assessment system. The study makes several policy suggestions and reveals that 70% of problems can be resolved by the Department, the University, and the University Grants Commission.
当前针对新冠肺炎疫情的在线学习研究存在样本不具代表性、问题封闭性、忽视学生改进意见等问题。此外,大多数研究都是在在线课程的前几周进行的,没有一项研究是针对大学水平的经济学学生的。本文采用便利抽样技术和开放式问题,收集了154名参加网络学习一年的大学经济学专业学生的数据。根据调查结果,在线课程的优势包括学生可以在家上课,避免健康风险,易于访问,灵活性,节省成本,减少学期损失的可能性,以及学习新技术。主要缺点是网络问题,理解主题的困难,不适合数学课程,注意力集中问题,非互动课程,财务限制,不利的健康影响,设备和互联网问题。缺点多于优点。学生们提出了一些建议:使用最先进的数字工具,录制和上传讲座,解决互联网和网络问题,按照固定的时间表上课,努力使主题更容易,缩短课程时间,机构支持,以及引入在线评估系统。该研究提出了若干政策建议,并显示70%的问题可以由学系、大学和大学教育资助委员会共同解决。
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引用次数: 0
Numerical Modeling and Analysis of HTM-Free Heterojunction Solar Cell Using SCAPS-1D 基于SCAPS-1D的无htm异质结太阳能电池数值模拟与分析
Pub Date : 2021-04-30 DOI: 10.26565/2312-4334-2021-2-11
D. Eli, A. Shuaibu, M.S. Ahmad, Jamila Tasiu
In this research paper, a HTM-free perovskite solar cell (PSC) structure with Titanium (TiO2), methyl ammonium lead triiodide (CH3NH3PbI3) and platinum (pt) as electron transport material (ETM), photon harvester and metal back contact is proposed. Solar Cell Capacitance Simulator (SCAPS-1D) program was used to implement the model and simulation. Effect of parameters such as thickness of ETM, thickness of absorber, doping concentration of ETM & absorber and electron affinity (EA) of ETM were investigated systematically. From the obtained results, it was found that the parameters affect the performance of the solar cell. When the thickness of ETM was varied from 0.02 to 0.10 μm. The results show that photovoltaic parameters decrease with the thickness increase. When the thickness of the absorber was varied from 0.1 to 1.0 μm, the optimized value was found at thickness of 0.4 . When the doping concentration of absorber and EMT were varied from 1010–1017 cm-3 and from 1015–1020 cm-3, the highest values of PCEs were obtained at 1016 cm-3 and 1020 cm-3 for Absorber and ETM. Also when the EA was varied in the range of 3.7 eV to 4.5 eV, the optimized value was at 3.7 eV. Upon optimization of the above mentioned parameters, power conversion efficiency (PCE) was found to be 25.75 %, short circuit current density (Jsc) 23.25 mAcm-2, open circuit voltage (Voc) 1.24 V and fill factor (FF) 89.50 %. The optimized result shows an improvement of ~1.95 times in PCE, ~1.06 times in Jsc, ~1.44 times in Voc and ~1.28 times in FF as compared to the initial device with the following parameters, PCE=13.22 %, Jsc=21.96 mAcm−2, Voc=0.86 V and FF=69.94 %.
本文提出了一种以钛(TiO2)、三碘化甲基铵铅(CH3NH3PbI3)和铂(pt)为电子传递材料(ETM)、光子收集器和金属背触点的无htm钙钛矿太阳能电池(PSC)结构。利用太阳能电池电容模拟器(SCAPS-1D)程序进行建模和仿真。系统地考察了ETM厚度、吸收层厚度、ETM和吸收层掺杂浓度以及ETM的电子亲和力等参数对ETM性能的影响。从得到的结果来看,这些参数对太阳能电池的性能有很大的影响。当ETM厚度在0.02 ~ 0.10 μm范围内变化时。结果表明,光伏参数随厚度的增加而减小。当吸收层厚度在0.1 ~ 1.0 μm范围内变化时,吸收层厚度在0.4 μm时达到最优值。当吸收剂和EMT的掺杂浓度在1010 ~ 1017 cm-3和1015 ~ 1020 cm-3范围内变化时,吸收剂和ETM的pce在1016 cm-3和1020 cm-3处达到最大值。当EA在3.7 ~ 4.5 eV范围内变化时,最优值为3.7 eV。优化后的功率转换效率(PCE)为25.75%,短路电流密度(Jsc)为23.25 mAcm-2,开路电压(Voc)为1.24 V,填充系数(FF)为89.50%。优化结果表明,与PCE= 13.22%, Jsc=21.96 mAcm−2,Voc=0.86 V, FF= 69.94%的初始器件相比,PCE提高了~1.95倍,Jsc提高了~1.06倍,Voc提高了~1.44倍,FF提高了~1.28倍。
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引用次数: 4
A Variational Technique for Thermodynamics of Liquid K(1-x)Rbx Alloys 液态K(1-x)Rbx合金热力学的变分技术
Pub Date : 2021-04-29 DOI: 10.26565/2312-4334-2021-2-09
R. C. Malan, A. Vora
Liquid K_(1-x) Rb_x binary alloys with various thermodynamical proportions of participating elements are investigated. The properties of thermodynamic interest are included in the study. The internal energy (Fint), Helmholtz free enrgy (FH) and the entropy (S) have been calculated in a concentration range from X=0.0 to X=1.0 increasing in a step of 0.1 in the present work. Apart from the internal energy (Fint), various contributions to this energy are also calculated and separately depicted in the present article. A variational approach has been adopted for the present calculation. A single potential with a set of two parameters is used for the calculation of all properties of the alloys. Static Hartree local field function (H) is used to consider screening effect. Various local field correction functions are used to take into account the exchange and correlation effect. Comparison with experimental data at some concentration shows the good agreement with the presently obtained data. With the help of current results, the applied model potential found very suitable with individual parameters for thermodynamical study. As the present results provide the data even where minimum availability of the experimental findings, it can serve as a data base for the future calculation which deals with thermodynamics of the liquid alloys. Present results allow one to get proportion based tuned properties of the K_(1-x) Rb_x for different requirements.
研究了不同参与元素热力学比例的液态K_(1-x) Rb_x二元合金。热力学性质也包括在研究中。本文计算了在X=0.0 ~ X=1.0浓度范围内,以0.1阶跃增加的内能(Fint)、亥姆霍兹自由能(FH)和熵(S)。除了内能(Fint)外,本文还计算并单独描述了对该能量的各种贡献。本计算采用了变分法。用一组有两个参数的单一电位来计算合金的所有性能。采用静态Hartree局部场函数(H)考虑筛分效果。为了考虑交换和相关效应,采用了各种局部场校正函数。与某些浓度下的实验数据进行比较,结果与目前得到的数据吻合较好。在现有结果的帮助下,发现所应用的模型势非常适合用于热力学研究的单个参数。由于本结果提供的数据,即使是最小的可用性的实验结果,它可以作为一个数据基础,为今后的计算处理的液体合金的热力学。目前的结果允许人们根据不同的要求得到K_(1-x) Rb_x的基于比例的调谐特性。
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引用次数: 0
Mode-Converting Corrugations for Cavities of Second-Harmonic Gyrotrons with Improved Performance 改进二次谐波回旋管腔的模转换波纹
Pub Date : 2021-04-10 DOI: 10.26565/2312-4334-2021-2-05
T. Tkachova, V. Shcherbinin, V. Tkachenko
Mode-converting longitudinal corrugations are used as a means of improving the selectivity properties of cavities for second-harmonic gyrotrons. As an example, 100-kW 0.3-THz second-harmonic gyrotron is considered. For the operating second-harmonic mode and most dangerous first-harmonic competing modes, the eigenvalues, ohmic losses and beam-wave coupling coefficients are investigated with respect to dimensions of a corrugated cavity. The most optimal parameters are found for a gyrotron cavity with mode-converting corrugations, which ensure the widest range of a single mode operation for the 0.3-THz second-harmonic gyrotron. It is shown that, in this range, the gyrotron output power can be increased up to 180 kW. It is found that output mode purity of the 0.3-THz second-harmonic gyrotron falls off due to mode-converting corrugations, which induce undesirable coupling of the operating mode with neighboring Bloch harmonics in the output section of the gyrotron cavity.
在二次谐波回旋管中,采用了一种改善腔体选择性的方法。以100kw的0.3太赫兹二次谐波回旋管为例。对于工作的二次谐波模式和最危险的一次谐波竞争模式,研究了波形腔的特征值、欧姆损耗和波束耦合系数与尺寸的关系。找到了具有模式转换波纹的回旋管腔的最优参数,保证了0.3太赫兹二次谐波回旋管单模工作的最宽范围。结果表明,在此范围内,回旋管输出功率可提高到180 kW。研究发现,0.3太赫兹二次谐波回旋管的输出模式纯度由于模式转换波纹而下降,从而导致回旋管腔输出部分的工作模式与邻近的布洛赫谐波产生不良耦合。
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引用次数: 1
Influence of Electron Injection on the Characteristics of a Hollow Cathode Glow Discharge 电子注入对空心阴极辉光放电特性的影响
Pub Date : 2021-01-01 DOI: 10.26565/2312-4334-2021-2-13
The article presents the results of experimental studies of a glow discharge with a hollow cathode in helium and argon gases using an auxiliary discharge as an electron emitter. The authors proposed to make the electrode common for both discharges in the form of a cylindrical metal mesh. The advantage of this design is explained as follows. The connection between the discharges is carried out through holes in the grid with a geometric transparency of 0.2, which makes it possible not only to smoothly control the glow discharge current, but also to enhance the discharge current. Plasma is known to be one of the most efficient electron emitters; however, its use as a cathode in devices with a glow discharge at low gas pressures is complicated by the fact that a grid with small holes is required to separate the electron flow from the plasma, and it is impractical to use such a system in view of low mechanical strength of the grid Since the hollow cathode works effectively at low gas pressures, the release of an electron flux from the plasma of some auxiliary discharge is possible with much larger holes in the grid separating the plasma and the hollow cathode cavity. In this case, the grid can be made such that it can withstand sufficiently high thermal loads and can operate in typical discharge modes with a hollow cathode. The injection of electrons into the cathode cavity of the glow discharge changes the radial distribution of the glow intensity, the width of the cathode dark space, and other parameters of the plasma in the cathode cavity. The influence of electrons penetrating from the auxiliary discharge into the cathode cavity of the main discharge becomes significant when the current of these electrons is comparable to or exceeds the current of electrons leaving the grid cathode surface as a result of γ-processes. In parallel with the measurement of the optical and electrical characteristics of the hollow cathode glow discharge plasma, measurements of the electron concentration were carried out by the microwave sounding method. The entire current of the auxiliary discharge penetrates into the cavity of the main discharge; however, after acceleration in the cathode dark space, the electrons penetrating from the auxiliary discharge ionize gas atoms and noticeably increase the current of the main discharge. Additional ions formed due to the ionization of the gas by the injected electrons knock out new electrons from the cathode surface, which makes it possible to increase the discharge current.
本文介绍了在氦气和氩气中用辅助放电作电子发射器的空心阴极辉光放电的实验研究结果。作者建议将电极以圆柱形金属网的形式用于两种放电。本设计的优点如下:放电之间的连接是通过几何透明度为0.2的网格孔进行的,这不仅可以平滑地控制辉光放电电流,而且可以增强放电电流。等离子体被认为是最有效的电子发射器之一;然而,它作为阴极在低气压辉光放电装置中的使用是复杂的,因为需要一个带有小孔的网格来将电子流与等离子体分开,而且考虑到网格的低机械强度,使用这样一个系统是不切实际的。在分隔等离子体和空心阴极腔的栅格上有更大的空穴,就有可能从辅助放电的等离子体中释放出电子通量。在这种情况下,可以使电网能够承受足够高的热负荷,并且可以在典型的空心阴极放电模式下运行。辉光放电将电子注入阴极腔内,改变了阴极腔内辉光强度的径向分布、阴极暗空间的宽度以及等离子体的其他参数。当从辅助放电穿透到主放电阴极腔的电子的电流相当于或超过由于γ-过程而离开栅极阴极表面的电子的电流时,这些电子的影响变得显著。在测量空心阴极辉光放电等离子体的光学和电学特性的同时,用微波测深法测量了电子浓度。辅助放电的全部电流贯穿到主放电腔内;然而,在阴极暗空间加速后,从辅助放电穿透的电子使气体原子电离,使主放电电流明显增大。由于注入的电子使气体电离而形成的额外离子从阴极表面敲出新的电子,这使得增加放电电流成为可能。
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引用次数: 1
الحماية الجنائية للأمن المجتمعي في التشريع العراقي 在伊拉克立法中对社区安全的刑事保护
Pub Date : 2021-01-01 DOI: 10.37940/jrls.2021.2.2.7
كمال عراك
ان تشريع القوانين لا يتم الا لمواجهة خطر يهدد أمن وسلامة المجتمع سواء كان الخطر موجه ضد الانسان نفسه أم الى حقوقه المالية أم الى أي شيءٍ آخر يعد من المقومات الاساسية لديمومة حياة الانسان واستمرارها، كما أن الشعوب لا تتقدم سياسياً واقتصاديًا وثقافيًا ما لم تشاع في مجتمعاتها اجواء السلام والوئام والانسجام، ونبذ الخلافات والنزاعات والصراعات الداخلية التي تهدد السلم والامن المجتمعي والتي تؤدي الى عدم استقرار الدولة، لذلك فقد اتجهت التشريعات الجنائية الى تجريم كل ما يمس سلامة الامن الاجتماعي عن طريق النصوص القانونية التي تعاقب على الافعال والسلوكيات التي من شأنها زعزعة امن المجتمع واستقراره ومنها قانون العقوبات العراقي، الذي نص على عدة جرائم تستهدف السلم والامن الاجتماعي، ونذكر منها جريمتين فقد نص على تجريم كلَّ ما يثير شعور الكراهية والبغضاء بين فئات المجتمع المتعدد دينيا او عرقيًا او مذهبيًا او قوميًا، وكذلك معاقبة كلًّ من يقوم بإثارة الحرب الأهلية والاقتتال الطائفي، وقررت عقوبات شديدة لمرتكبي هذه الجرائم، ولا يشترط تحقق النتيجة الجرمية لقيام الجريمة، إذ إن الجريمة تتحقق بمجرد اقتراف الفاعل نشاطًا اجراميًا يستهدف إثارة شعور الكراهية أو إثارة الحرب الاهلية والاقتتال، حتى إن لم تتحقق النتيجة، كونها من الجرائم الشكلية او جرائم الخطر والتي لا يتصور الشروع فيها فهي اما أن تقع تامة او لا تقع . وعليه فقد حرص قانون العقوبات العراقي النافذ على توفير الحماية اللازمة للمجتمع وتنظيم العلاقات بين أفراده أو طوائفه أو مكوناته المتعددة لا سيما أن المجتمع العراقي متعدد الأطياف، فشدد العقاب على كلَّ اعتداء يستهدف اي فئة او طائفه بسبب انتمائها الديني أو العرقي أو القومي أو المذهبي الكلمات المفتاحية: جرائم الامن المجتمعي، جرائم أمن الدولة الداخلي، جرائم السلم الاهلي، جرائم النسيج الاجتماعي، جرائم تقويض للسلم المجتمعي
法律的制定是为了消除对社会安全与安全的威胁,无论这种威胁是针对人本身,还是针对他们的经济权利,还是针对其他构成人类生存和生存的基本因素的威胁。只有在社会中普遍存在和平、和谐与和谐的气氛时,人民才能在政治、经济和文化上取得进步。对可能破坏社会安全与稳定的行为和行为,包括伊拉克《刑法典》,其中规定了几项危害社会和平与安全的罪行,其中两项罪行,它规定,在多宗教、种族、教派或民族社会群体之间煽动仇恨和仇恨的行为均应定为刑事犯罪,并规定对任何挑起内战和教派纷争的人都应受到惩罚,并规定了对这些罪行的严厉处罚,因为犯罪行为一旦发生,则不要求犯罪的犯罪后果。犯罪实施旨在煽动仇恨或内战和战斗的犯罪活动,即使其结果未实现,其犯罪行为是形式犯罪或危险犯罪,其实施方式不可想象,要么完全发生,要么不发生。因此,伊拉克现行的《刑法》确保为社会提供必要的保护,并规范其成员、社区或多个组成部分之间的关系,特别是因为伊拉克社会是多族裔的,它加重了对基于宗教、种族、民族或思想倾向而针对任何群体或群体的攻击的惩罚:社区安全罪、国内安全罪、国内和平罪、社会结构罪、破坏社会和平罪。
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引用次数: 0
Modeling and Simulation of Lead-Free Perovskite Solar Cell Using SCAPS-1D 基于SCAPS-1D的无铅钙钛矿太阳能电池建模与仿真
Pub Date : 2021-01-01 DOI: 10.26565/2312-4334-2021-2-12
In this work, the effect of some parameters on tin-based perovskite (CH3NH3SnI3) solar cell were studied through device simulation with respect to adjusting the doping concentration of the perovskite absorption layer, its thickness and the electron affinities of the electron transport medium and hole transport medium, as well as the defect density of the perovskite absorption layer and hole mobility of hole transport material (HTM). A device simulator; the one-dimensional Solar Cells Capacitance Simulator (SCAPS‑1D) program was used for simulating the tin-based perovskite solar cells. The current-voltage (J-V) characteristic curve obtained by simulating the device without optimization shows output cell parameters which include; open circuit voltage (Voc) = 0.64V, short circuit current density (Isc) = 28.50mA/, fill factor (FF) = 61.10%, and power conversion efficiency (PCE) = 11.30% under AM1.5 simulated sunlight of 100mW/cm2 at 300K. After optimization, values of the doping concentration, defect density, electron affinity of electron transport material and hole transport material were determined to be: 1.0x1016cm-3, 1.0x1015cm-3, 3.7 eV and 2.3 eV respectively. Appreciable values of solar cell parameters were obtained with Jsc of 31.38 mA/cm2, Voc of 0.84 V, FF of 76.94% and PCE of 20.35%. when compared with the initial device without optimization, it shows improvement of ~1.10 times in Jsc, ~1.80 times in PCE, ~1.31 times in Voc and ~1.26 time in FF. The results show that the lead-free CH3NH3SnI3 perovskite solar cell which is environmentally friendly is a potential solar cell with high theoretical efficiency of 20.35%.
本文通过器件模拟研究了钙钛矿吸收层掺杂浓度、钙钛矿吸收层厚度、电子输运介质和空穴输运介质的电子亲和度、钙钛矿吸收层缺陷密度和空穴输运材料(HTM)的空穴迁移率等参数对锡基钙钛矿(CH3NH3SnI3)太阳能电池的影响。设备模拟器;利用一维太阳能电池电容模拟器(SCAPS‑1D)程序模拟锡基钙钛矿太阳能电池。模拟未优化器件得到的电流-电压(J-V)特性曲线显示了输出电池参数,包括:在300K、100mW/cm2的AM1.5模拟日光下,开路电压Voc = 0.64V,短路电流密度Isc = 28.50mA/,填充系数FF = 61.10%,功率转换效率PCE = 11.30%。优化后,电子输运材料和空穴输运材料的掺杂浓度、缺陷密度、电子亲和度分别为:1.0 × 1016cm-3、1.0 × 1015cm-3、3.7 eV和2.3 eV。在Jsc为31.38 mA/cm2, Voc为0.84 V, FF为76.94%,PCE为20.35%的条件下,获得了较为理想的太阳能电池参数。与未优化的初始装置相比,Jsc提高了~1.10倍,PCE提高了~1.80倍,Voc提高了~1.31倍,FF提高了~1.26倍。结果表明,无铅CH3NH3SnI3钙钛矿太阳能电池具有较高的理论效率(20.35%),是一种有潜力的环境友好型太阳能电池。
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引用次数: 6
النظام القانوني لمجلس الخدمة العامة الأتحادي 联邦公务员制度委员会的法律制度
Pub Date : 2021-01-01 DOI: 10.37940/jrls.2021.2.2.5
ضياء عماد عبد علي
مجلس الخدمة العامة الاتحادي في العراق يعد أحد أهم الأجهزة المستقلة في العراق تم النص عليه في المادة (107) من الدستور العراقي لعام 2005م ليتولى تنظيم شؤون الوظيفة العامة الاتحادية، وقد ترك النص الدستوري تنظيم تكوين المجلس واختصاصاته إلى قانون يسن من قبل السلطة التشريعية لهذا الغرض، وبالفعل صدر قانون مجلس الخدمة العامة الاتحادي رقم (4) لسنة 2009م المعدل ليضع التفصيلات لهذا المجلس الحيوي والمهم. فقد أعيد العمل بمجلس الخدمة العامة للضرورة الملحة في ظل غياب المعايير اللازمة في مجال الوظيفة العامة وما يرتبط بها والغبن الذي لحق بشرائح مختلفة من أفراد المجتمع، ولحاجة مؤسسات الدولة إلى وجود جهة تنظم شؤون الوظيفة العامة وتضع القواعد الأساسية لتلك المؤسسات على أساس الكفاءة والمهنية لتحقيق المصلحة العامة، فوجود جهة مستقلة تضمن تحقيق العدالة الاجتماعية والشفافية بات أمرًا ضروريًا، وعليه يعقد الأمل على مجلس الخدمة العامة الاتحادي لتحقيق ذلك. الكلمات المفتاحية: النظام، مجلس الخدمة العامة الاتحادي، الاستقلال، الدستور، القانون، الوظيفة العامة
2005年《伊拉克宪法》第107条规定,伊拉克联邦公务员委员会是伊拉克最重要的独立机构之一,该委员会的组成和职权由立法机关为此目的通过的一项法律来规定。公共服务委员会由于缺乏必要的公共服务标准和相关标准以及社会各阶层的不平等而被重新启用,国家机构需要有一个负责公共事务的机构,并根据公共利益的能力和专业精神为这些机构制定基本规则。因此,一个确保社会公正和透明度的独立机构至关重要,因此,联邦公务员制度委员会有希望做到这一点。关键词:系统、联邦公务员委员会、独立、宪法、法律、公职
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引用次数: 0
Investigation on Electrical Properties of Solid Polymer Sheets (HDPE AND LDPE) at Audio Frequency Range 固体聚合物片材(HDPE和LDPE)在音频范围内的电性能研究
Pub Date : 2021-01-01 DOI: 10.26565/2312-4334-2021-2-10
Two different groups of solid polymer sheets: low density polyethylene (LDPE) sample of thickness 0.006 cm and 0.007 cm along with high density polyethylene (HDPE) sample of the thickness of 0.009 cm, 0.010 cm were taken in this work. The measurement of electrical properties such as dielectric constant, ε' and dielectric loss, ε'' for LDPE and HDPE polymer sheets have been measured using a dielectric cell. The dielectric cell has been fabricated which consists of two circular parallel plates of pure stainless steel each of 5 cm diameter and 2 mm thickness. An impedance bridge (GRA 650A) was used for measurement of capacitance, C, and dissipation factor, D in the audio frequency (AF) range, 100 Hz to 10 kHz. Different samples were loaded in between the two plates of the cell and the capacitance as well as the dissipation factor were estimated from the dial readings of the bridge. Effect of frequency variation on ε', ε'', relaxation time, τ , dissipation factor, tanδ and ac conductivity, σ were also discussed at audio frequency range. The complex permittivity, ε*, related to free dipole oscillating in an alternating field and loss tangent, tanδ were calculated. The frequency-dependent conductivity, dielectric behavior, and electrical modulus, both real (M') and imaginary (M") parts of LDPE and HDPE have been studied in this work. The values of the real part of the electrical modulus (M') did not equal to zero at low frequencies and it is expected that the electrode polarization may develop in both sheets. These findings reveal an increased coupling among the local dipolar motions in a short-range order localized motion. The analysis of real (ε') and imaginary (ε'') parts of dielectric permittivity and that electrical modulus real (M') and imaginary (M") parts signify poly dispersive nature of relaxation time as observed in Cole-Cole plots.
采用两组不同的固体聚合物片材:厚度分别为0.006 cm和0.007 cm的低密度聚乙烯(LDPE)样品和厚度分别为0.009 cm和0.010 cm的高密度聚乙烯(HDPE)样品。用介质电池测量了LDPE和HDPE聚合物片材的介电常数ε′和介电损耗ε′等电性能。电介质电池由两个直径为5厘米,厚度为2毫米的纯不锈钢圆形平行板组成。阻抗桥(GRA 650A)用于测量100 Hz至10 kHz音频(AF)范围内的电容C和耗散因子D。在电池的两个极板之间加载不同的样品,并根据电桥的表盘读数估计电容和耗散系数。讨论了频率变化对音频范围内ε′、ε′′、弛豫时间、τ、耗散因子、tanδ和交流电导率σ的影响。计算了交变场中自由偶极子振荡的复介电常数ε*和损耗正切tanδ。本文研究了LDPE和HDPE的实数部分(M′)和虚数部分(M′)与频率相关的电导率、介电行为和电模量。在低频时,电模量的实部(M′)不等于零,预计两片电极都可能发生极化。这些发现揭示了局域偶极运动在近程序定域运动中耦合性的增强。电介质介电常数的实部(ε′)和虚部(ε′)以及电模量的实部(M′)和虚部(M′)的分析表明,在Cole-Cole图中观察到弛豫时间的多色散性质。
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引用次数: 0
Modeling of Molecular Mechanisms of Radiation Adaptive Response Formation 辐射适应性反应形成的分子机制建模
Pub Date : 2021-01-01 DOI: 10.26565/2312-4334-2021-2-16
The phenomenon of adaptive response is expressed in the increase of resistance of a biological object to high doses of mutagens under the conditions of previous exposure to these (or other) mutagens in low doses. Low doses of mutagen activate a number of protective mechanisms in a living object, which are called hormetic. Thus, the adaptive response and hormesis are links in the same chain. Radiation hormesis refers to the generally positive effect of low doses of low LET radiation on biological objects. The phenomenology of radiation-induced adaptive response and radiation hormesis for biological objects of different levels of organization is considered; the review of existing theories describing the dose-effect relationship has been reviewed. The hypothesis proposing one of the mechanisms of formation of radiation adaptive response of cells taking into account the conformational structure of chromatin has been submitted. The analysis of modern concepts of the phenomenon of hormesis on the basis of modeling of molecular mechanisms of formation of hormetic reactions to low-dose low LET radiation has been carried out. The parameters that can be used for quantitative and graphical evaluation of the phenomenon of hormesis was considered, and a formula for calculating the coefficient of radiation-induced adaptive response has been proposed. A review of mathematical models describing the radiation relative risk of gene mutations and neoplastic transformations at low-dose irradiation of cohorts has been performed. The following conclusions have been made: radiation hormesis and adaptive response are generally recognized as real and reproducible biological phenomena, which should be considered as very important phenomena of evolutionarily formed biological protection of living organisms from ionizing radiation. The hormesis model of dose-response relationship makes much more accurate predictions of a living object's response to radiation (or other stressors) in the low-dose range than the linear threshold (LNT) model does. The LNT model can adequately describe reactions only in the region of high doses of radiation, and, therefore, extrapolation modeling of biological object’s reactions from the zone of high doses to low doses is not correct.
适应性反应现象表现为生物对象在先前低剂量暴露于这些(或其他)诱变剂的条件下,对高剂量诱变剂的抵抗力增加。低剂量的诱变剂会激活生物体的一些保护机制,这些机制被称为激效。因此,适应性反应和激效是同一链条上的环节。辐射激效是指低剂量低LET辐射对生物物体产生的普遍积极作用。考虑了不同组织水平的生物对象的辐射诱导适应反应和辐射激效的现象学;对现有的描述剂量效应关系的理论进行了综述。提出了一种考虑染色质构象结构的细胞辐射适应性反应形成机制的假说。在对低剂量低LET辐射致敏反应形成的分子机制进行建模的基础上,对致敏现象的现代概念进行了分析。考虑了可用于定量和图解评价激效现象的参数,并提出了辐射诱导自适应响应系数的计算公式。对描述低剂量辐照下基因突变和肿瘤转化的辐射相对风险的数学模型进行了综述。研究结果表明:辐射激效和适应反应是公认的真实的、可复制的生物现象,是生物对电离辐射进行生物保护的重要进化过程。剂量-反应关系的激效模型比线性阈值(LNT)模型更准确地预测了低剂量范围内生物对辐射(或其他应激源)的反应。LNT模型只能充分描述高剂量辐射区域的反应,因此,生物物体从高剂量区到低剂量区的反应的外推模型是不正确的。
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引用次数: 1
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La Ricerca scientifica. 2. ser., pt. 2: Rendiconti. Sezione B: Biologica
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