Coordination compounds in biology The chemistry of vitamin B12 and model compounds

Vitamin B₁₂ is an important coordination compound in biology. It is an interesting biomolecule in the sense that no other vitamin contains a metal ion. This is the only naturally occurring organometallic compound found in biology. An intriguing aspect of vitamin B₁₂ is the great stability of the metal-carbon bond. A great deal of new and interesting inorganic chemistry has been uncovered while studying systems pertinent to B₁₂. In this article some salient features of this unique molecule (B₁₂) and its model compounds are presented.     

Effect of vitamin B12on cleft palate induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin and dexamethasone in mice简

The purpose of this study was to investigate the effect of vitamin B₁₂ on palatal development by co-administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and dexamethasone (DEX). We examined the morphological and histological features of the palatal shelf and expression levels of key signaling molecules (transforming growth factor-β3 (TGF-β3) and TGF-β type I receptor (activin receptor-like kinase 5, ALK5)) during palatogenesis among a control group (Group A), TCDD+DEX exposed group (Group B), and TCDD+DEX+vitamin B12 exposed group (Group C). While we failed to find that vitamin B12 decreased the incidence of cleft palate induced by TCDD+DEX treatment, the expression levels of key signaling molecules (TGF-β3 and ALK5) during palatogenesis were significantly modulated. In TCDD+DEX exposed and TCDD+DEX+vitamin B12 exposed groups, palatal shelves could not contact in the midline due to their small sizes. Our results suggest that vitamin B12 may inhibit the expression of some cleft palate inducers such as TGF-β3 and ALK5 in DEX+TCDD exposed mice, which may be beneficial against palatogenesis to some degree, even though we were unable to observe a protective role of vitamin B12 in morphological and histological alterations of palatal shelves induced by DEX and TCDD.     

Electronic structure and magnetism ofRMn6Sn6 (R=Tb, Dy)

This article reports first-principles band structure calculations forRMn₆Sn₆ (R=Tb, Dy). The calculation uses the linear muffin-tin orbitals (LMTO) method in the atomic-sphere-approximation (ASA), and yields results showing that both TbMn₆Sn₆ and DyMn₆Sn₆ are ferrimagnetic compounds with antiparallel aligned moments ofR and Mn atoms. In this research the 4f states ofR atoms are treated as localized states, i.e., the hybridization of 4f states with other valence electrons is neglected. The moments of Mn in both compounds were determined to be 2.43 μ_B and 2.38 μ_B, respectively. The considerably small additional moments for Mn from the spin-orbit coupling indicates that the spin-orbital coupling is not dominated for Mn atoms. The total moments of Tb and Dy atoms are 10.28 μ_B and 11.20 μ_B. All the calculation findings accorded well with experimental results. Project supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry of China.     

Role of vitamin B12 on methylmalonyl-CoA mutase activity

Vitamin B₁₂ is an organometallic compound with important metabolic derivatives that act as cofactors of certain enzymes, which have been grouped into three subfamilies depending on their cofactors. Among them, methylmalonyl-CoA mutase (MCM) has been extensively studied. This enzyme catalyzes the reversible isomerization of L-methylmalonyl-CoA to succinyl-CoA using adenosylcobalamin (AdoCbl) as a cofactor participating in the generation of radicals that allow isomerization of the substrate. The crystal structure of MCM determined in Propionibacterium freudenreichii var. shermanii has helped to elucidate the role of this cofactor AdoCbl in the reaction to specify the mechanism by which radicals are generated from the coenzyme and to clarify the interactions between the enzyme, coenzyme, and substrate. The existence of human methylmalonic acidemia (MMA) due to the presence of mutations in MCM shows the importance of its role in metabolism. The recent crystallization of the human MCM has shown that despite being similar to the bacterial protein, there are significant differences in the structural organization of the two proteins. Recent studies have identified the involvement of an accessory protein called MMAA, which interacts with MCM to prevent MCM’s inactivation or acts as a chaperone to promote regeneration of inactivated enzyme. The interdisciplinary studies using this protein as a model in different organisms have helped to elucidate the mechanism of action of this isomerase, the impact of mutations at a functional level and their repercussion in the development and progression of MMA in humans. It is still necessary to study the mechanisms involved in more detail using new methods.     

Interest in biology. Part I: A multidimensional construct

Interest in a school subject (e.g., biology) is conceptualized in terms of three components: topics, activities, and motives, each of which has several dimensions. In this study, seven instruments were developed and administered to grade-10 biology students in Israel. Factor analysis provided support for the conceptualization which underlies the development of the instruments. Topic dimensions included biochemical processes, nonhuman organisms, human biology, personal hygiene, and practical applications; the activity dimensions were experiential learning, reception learning, writing/summarizing and group discussion; motives included environmental issues, moral issues, examination success, personal independence, problem solving, and four career dimensions (research, high-status professions, lower-status careers, “woodsy-birdsy” careers). In an analysis described in Part II of this paper, the students were classified into four groups on the basis of their grade-11 subject enrollment intentions: H (high-level biology), L (low-level biology), P (physical science), and N (no science). Zero-order and multiple correlations were found between interest and other variables and membership/nonmembership of the four groups. Students in Group H were characterized by higher achievement in year-10 biology, higher levels of enjoyment of biology, career orientations towards research or high-status biology-based professions, greater interest in various biology topics, especially reproduction/cell division/genetics, and a greater tendency to regard the Bagrut (grade-12) examination as interesting. Students in Group N displayed lower levels of interest in various topics (especially the microscope, plants, and reproduction), were less motivated to solve problems, had poorer grades in biology (and chemistry), were less likely to perceive biology as useful, were less likely to regard the Bagrut examination as fair, and were less likely to be interested in social modes of learning. There were few associations between interest variables and membership in Groups L or P.     

解矩阵方程sum (A_1X_1B_1=C) from l=1 to N反对称解的一个迭代算法

对于求解线性矩阵方程sum (A_1X_1B_1=C) from l=1 to N的反对称解X_1,X_2,...,X_N的问题,文章给出一个迭代算法,用这个算法可判断方程是否存在反对称解。若如果矩阵方程相容,就可以通过有限步的迭代之后得到反对称解;若选择特定的初始值,则通过迭代之后得到的是它的极小范数反对称解。     

Yellapragada SubbaRow

This is the story of a determined Indian who strived very hard and achieved greatness. He went to Harvard Medical School with very little money, braved many grave hardships and eventually fulfilled his ambitions to a large extent. Yellapragada SubbaRow did research in Harvard Medical School in biological chemistry and directed research at Lederle Laboratories, a pharmaceutical giant near New York. He played an important part in several historic and extraordinary discoveries made in biological chemistry and medicine during 1924?C1948. Some of the important ones are phosphocreatine, adenosine triphosphate, vitamin B₉, antifolate cancer drugs, filaricides and antibiotics. He made many personal sacrifices to accomplish what he wanted to. He received little recognition during his lifetime, but is now hailed as one of the most eminent medical minds of the century.     

Activity optimization method in SPECT： A comparison with ROC analysisActivity optimization method in SPECT： A comparison with ROC analysis

A discriminant method for optimizing activity in nuclear medicine studies is validated by comparison with ROC （received operating characteristic）-curves. The method is tested in 21 single photon emission computerized tomography （SPECT）, performed with a cardiac phantom. Three different lesions （Lb L2 and L3） were placed in the myocardium-wall by pairs fbr each SPECT. Three activities （84, 37 or 18.5 MBq） of 99mTc were used as background. Linear discriminant analysis was used to select the parameters that characterize image quality among the measured variables in the images [（Background-to-Lesion （B/Li） and Signal-to-Noise （S/N） ratios）]. Two clusters with different image quality （P=0.021 ） were obtained. The ratios B/Lj, B/L2 and B/L3 are the parameters used to construct the function with 100% of cases correctly classified into the clusters. The value of 37 MBq was the lowest tested activity for which good results for the B/Li ratios were obtained. The result coincides with the applied ROC-analysis （r=0.89）.     

Students’ motivation in biology lessons—can student autonomy reduce the gender gap?

When it comes to biology lessons in Germany, girls generally exhibit higher levels of self-determined motivation than boys. Previous research suggests that fostering student autonomy could be a way to effectively address this gender gap. To investigate gender-related effects in biology education, a sample of 303 sixth-grade students (M_age = 11.31 years, SD_age = 0.58 years) participated in a 3-h teaching unit on harvest mice that was taught in either an autonomy-supportive or controlling manner. The results revealed a significant effect of the treatment on self-determined motivation, with the effect being stronger for the boys. In the treatment with controlling teaching behavior, gender-related differences in self-determined motivation became apparent. In contrast, the gender gap was mainly smaller in the treatment with autonomy-supportive teaching behavior. Thus, the results suggest that satisfying the need for autonomy appears to be an effective means to help bridge the gender gap in biology lessons.

     

Chemical composition and antioxidant activity of certain <Emphasis Type="Italic">Morus</Emphasis> species

In the present work, the fruits of four Morus species, namely Morus alba (white mulberry), Morus nigra (black mulberry), Morus laevigata (large white fruit), and Morus laevigata (large black fruit), were analyzed for proximate composition, essential minerals, and antioxidant potentials. For this purpose, the ripe fruits were collected from the northern regions of Pakistan. The major nutritional components (moisture, ash, lipids, proteins, fibres, carbohydrates, and total sugar) were found to be in the suitable range along with good computed energy. Total dry weight, pH, and titratable acidity (percent citric acid) were (17.60±1.94)–(21.97±2.34) mg/100 g, (3.20±0.07)–(4.78±0.15), and (0.84±0.40)%–(2.00±0.08)%, respectively. Low riboflavin (vitamin B₂) and niacin (vitamin B₃) contents were recorded in all the fruits, while ascorbic acid (vitamin C) was in the range from (15.20±1.25) to (17.03±1.71) mg/100 g fresh weight (FW). The mulberry fruits were rich with regard to the total phenol and alkaloid contents, having values of (880±7.20)–(1650±12.25) mg/100 g FW and (390±3.22)–(660±5.25) mg/100 g FW, respectively. Sufficient quantities of essential macro-(K, Ca, Mg, and Na) and micro-(Fe, Zn, and Ni) elements were found in all the fruits. K was the predominant element with concentration ranging from (1270±9.36) to (1731±11.50) mg/100 g, while Ca, Na, and Mg contents were (440±3.21)–(576±7.37), (260±3.86)–(280±3.50), and (240±3.51)–(360±4.20) mg/100 g, respectivly. The decreasing order of micro-minerals was Fe>Zn>Ni. The radical scavenging activity of methanolic extract of fruits was concentration-dependent and showed a correlation with total phenolic constituents of the respective fruits. Based on the results obtained, mulberry fruits were found to serve as a potential source of food diet and natural antioxidants.     

领悟新课程理念 构建新型生物课堂

课堂教学是新课程实施的基本途径。如何做到让课堂教学高效、活泼、趣味十足,如何在生物课堂上真正贯彻新课程理念,是对当代教育工作者提出的一个巨大挑战,这就需要我们生物教师不断革新教学模式,构建新型生物课堂。     

领悟新课程理念构建新型生物课堂

课堂教学是新课程实施的基本途径。如何做到让课堂教学高效、活泼、趣味十足,如何在生物课堂上真正贯彻新课程理念,是对当代教育工作者提出的一个巨大挑战,这就需要我们生物教师不断革新教学模式,构建新型生物课堂。     

高中生物趣味性教学方法探析

生物是高中阶段的重要教学内容之一,在高中阶段学生要学习的学科数目多,学习任务重,学生的压力很大,此时对于学科的学习兴趣就成为激发学生学习积极性的主要动力,只有学生对学习内容有兴趣才能使学生面对沉重学习任务时也能保持积极的学习态度,学习质量才能有所保证。因此,教师在教学时,除了要达到教育目标,更要让生物教学具备趣味性,为此,本文主要研究高中生物趣味性教学方法的有效实施策略。     

Curie temperature of the intergranular amorphous phase in nanocrystalline Fe89Zr7B4 alloy

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由植物油提取的合成润滑剂的流变特性和摩擦特性

The double bonds in the vegetable oils can be conjungated and Diels-Alder react when they are heated in the existence of the catalyst. The percent of the double bond will decrease and the oxidative stability of the vegetable oils can be ameliorated. Dimmer acid can react with different carbon chain length of alcohols to form dimmer acid esters. A series of dimmer acid esters were synthesized and their rheological characteristics （viscosity, viscosity index, pour point） and tribological characteristics （the coefficient of friction at different load, the characteristic of extreine pressure （ PB ）, the wear scare diameter （ D30min^196N ） were evaluated and analyzed. The results showed that the characteristics of Di-iso-octanol dimmer acid ester were the best among the synthesized dimmer esters. It＇ s a lubricant with good properties（the viscosity is 94.5 mm^2/s, the viscosity index is high up to 141 and the pour point is - 49℃ ）. It is a kind of newly interesthing ester type lubricant. Its rheological and tribological characteristics are even better than those of the slap-up synthesized lubricant--pentaerythritol esters （C7-9 acidate）. The FT-IR spectrophotometer was used to analyze the structure of the synthetic esters. Their IR spectra are the same as the typical IR spectrum of ester. The test indicated that Di-iso-octanol dimmer acid ester could be used as a kind of base lubricant with excellent quantity.     

Bearing capacity of thin-walled shallow foundations: an experimental and artificial intelligence-based study

Thin-walled spread foundations are used in coastal projects where the soil strength is relatively low. Developing a predictive model of bearing capacity for this kind of foundation is of interest due to the fact that the famous bearing capacity equations are proposed for conventional footings. Many studies underlined the applicability of artificial neural networks (ANNs) in predicting the bearing capacity of foundations. However, the majority of these models are built using conventional ANNs, which suffer from slow rate of learning as well as getting trapped in local minima. Moreover, they are mainly developed for conventional footings. The prime objective of this study is to propose an improved ANN-based predictive model of bearing capacity for thin-walled shallow foundations. In this regard, a relatively large dataset comprising 145 recorded cases of related footing load tests was compiled from the literature. The dataset includes bearing capacity (Q_u), friction angle, unit weight of sand, footing width, and thin-wall length to footing width ratio (L_w/B). Apart from Q_u, other parameters were set as model inputs. To enhance the diversity of the data, four more related laboratory footing load tests were conducted on the Johor Bahru sand, and results were added to the dataset. Experimental findings suggest an almost 0.5 times increase in the bearing capacity in loose and dense sands when L_w/B is increased from 0.5 to 1.12. Overall, findings show the feasibility of the ANN-based predictive model improved with particle swarm optimization (PSO). The correlation coefficient was 0.98 for testing data, suggesting that the model serves as a reliable tool in predicting the bearing capacity.     

Reliability analysis of DOOF for weibull distribution

Hierarchical Bayesian method for estimating the failure probabilityp _i under DOOF by taking the quasi-Beta distributionB(p _i−1, 1, 1,b) as the prior distribution is proposed in this paper. The weighted Least Squares Estimate method was used to obtain the formula for computing reliability distribution parameters and estimating the reliability characteristic values under DOOF. Taking one type of aerospace electrical connector as an example, the correctness of the above method through statistical analysis of electrical connector accelerated life test data was verified. Project (No. 59975081) supported by the National Natural Science Foundation of China     

Structure and magnetic properties of Fe73.5Ag1Nb3Si13.5B9 alloy

The magnetic properties of as-quenched and annealed Fe_73.5Ag₁Nb₃Si_13.5B₉ alloys were investigated. X-ray diffraction was used to monitor the structure changes of the samples under different annealing temperatures. It was found that by Cu addition, the crystallization temperature T _x1 of Fe-Nb-Si-B alloy is decreased, whereas by Ag addition, the T _x1 is increased. A small amount of α-Fe and Ag were obtained after the sample was annealed at 500°C for 1 h. With increasing the annealing temperature, Fe₂₃B₆, Fe₂B, Fe₃B were separated out and magnetic properties of the samples were impaired quickly. A mostly single nanocrystalline grain of a-Fe phase could not be obtained in the annealed samples.     

Language use in kindergarten science lessons: language production and academic language during a video feedback coaching intervention in kindergarten science lessons

This paper aims to gain insight into language production and academic language of 4- and 5-year-old students and their teachers in the course of a teacher intervention during kindergarten science education. The study is based on videotaped classroom observations, and specifically focuses on the academic language use of students (N_intervention = 18, N_controls = 26) and teachers (N_intervention = 5, N_controls = 5). The results suggest that this general teacher intervention yields interesting changes in language use and production. Patterns of change over time confirm the idiosyncratic and non-linear nature of these changes. Science lessons represent an appropriate context in which to acquaint students with academic language, which can be used as a basis to build upon more sophisticated language skills.     

Students' Perception of Biology Fieldwork: The example of students undertaking a preliminary year at a UK university

It is widely held among biology teachers that fieldwork is valuable, but little is heard about students' perception of fieldwork or about the reasons for their liking or disliking fieldwork. This paper uses data from students to explore the hypotheses (1) that biology students with a positive perception of fieldwork have a less positive perception of laboratory work and vice versa and (2) that perception of fieldwork is related to demographic/personal factors and/or to pre-university perceptions and experience of fieldwork. Numeric indices of appreciation of biology field and laboratory work (I _field and I _lab) were determined using questionnaire information from 54 students. I _field and I _lab were positively correlated and there was no evidence of polarization of views; the problem that some students have a poor perception of both needs to be addressed. Mature students had a more positive view of fieldwork than 18–20-year-olds. However, regression analysis of I _field against principal components suggested that demographic/personal factors had relatively little overall influence (< 20%) on appreciation of fieldwork. Perception of fieldwork at university was related to the rank given to fieldwork when choosing a university course. However, students who had participated in pre-university fieldwork did not have a more positive perception of university fieldwork; although students who recalled a worst memory of pre-university fieldwork had a less positive perception of fieldwork at university. The seeming mixed relevance of pre-university fieldwork suggests that the relationship between perception of fieldwork undertaken at university and quality of pre-university fieldwork is an area for future research.