bluuebunny/crossref_metadata_2025 huggingface dataset:
Method of determining parameters of void growth damage model and its application to simulation of spall test
Authors: Zhang Feng-Guo , Liu Jun , He An-Min , Wang Pei , Wang Kun , Zhou Hong-Qiang , Zhao Fu-Qi ,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
Published: November 2020

Spallation of ductile metal is of great importance in many scientific and engineering fields, which is due to the interaction between the incident shock waves and the reflected waves. Physically, the spallation is caused by nucleation, growth and coalescence of microvoids for ductile material. Therefore, numerical simulation of spall process usually involves theoretical model of void growth. However, due to the limited knowledge of microvoid properties, many empirical parameters are included in the void growth model, which are usually determined by comparing numerical results with experimental data. Therefore, a key problem arises in the numerical modeling of damage and spall fracture, that how the parameters of the void growth damage model can be determined. In this work, we present a theoretical method to determine the parameters based on the free surface velocity (FSV) profile. Firstly, the critical state of damage is discussed based on the relationship between characteristics of FSV and change of physical quantity in spall plane. Then, the propagation and interaction of shock waves during the evolution of spall damage are considered. Lastly, the physical meanings of the parameters of the void growth damage model are further discussed. So, based on the relation among spall strength, damage and pull-back of FSV, a physics-based method to determine the parameters of the model is given. The applicability of this method is verified by the simulation of the spall experimental data on typical ductile metals OFHC copper and tantalum. The parameter-determining method given in this paper can not only expand the scope of application of the damage model and effectively improve the reliability of the calculation results, but also provide a good reference for the determination of parameters of other spall damage model.
High-order natural transition simulation method based on deep residual network
Authors: Zheng Tian-Yun , Wang Sheng-Ye , Wang Guang-Xue , Deng Xiao-Gang ,   College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China,   School of Physics, Sun Yat-sen University, Guangzhou 510275, China
Published: November 2020

Turbulence model combined with machine learning is one of the research hotspots in fluid mechanics. The existing approaches reconstruct or modify the turbulence eddy viscosity or Reynolds stress based on the experimental/numerical data. In this paper, we reconstruct the mapping function between intermittency and the mean flow variables by deep neural network (ResNet), developing an quasi-algebraic transition model coupled with the Spallart-Allmaras (SA) model. We mainly concentrate on the natural transition flows and take the results calculated by the computational fluid dynamics solver with the SST-γ-Reθ model as the training data. Seventeen local mean flow quantities satisfying the Galilean invariants are selected as the input features. Five-time cross validation is performed to avoid overfitting. Combining with the high-precision weighted compact nonlinear format, S&K, T3a- transition plate and S809 airfoil are used to test the performance of the model. The results are compared with those from the SST-γ-Reθ transition model, showing that the pure data-driven ResNet model can predict the intermittent field accurately, which greatly improves the ability of SA model to simulate the natural transition flow. For the example of S&K and T3a- transition plate, the comparison of wall friction shows that the SA-ResNet model is in good agreement with the experimental result, but the BC model, which is also an algebraic model, predicts the transition position of the T3a- transition plate model prematurely. The training data do not contain any numerical solution about airfoil, but the model can still be applied to the case of S809 airfoil with different attack angles. The predicted results of lift resistance characteristics, frictional coefficient distribution and transition position are close to the results from the SST-γ-Reθ transition model. On this basis, another advantage of the model is the solution efficiency. The efficiency is improved more significantly in the case with larger mesh quantity. With the same convergence accuracy, the CPU time required by the SA-ResNet model for the S&K plate case is 85.6% that of the SST-γ-Reθ transition model, while the CPU time required by the S809 airfoil with a larger mesh volume is only 67.2% that of the later model. This study demonstrates the great potential of machine learning in the construction of transition models.
S/X dual-band real-time modulated frequency selective surface based absorber
Authors: Zhou Shi-Hao , Fang Xin-Yu , Li Meng-Meng , Yu Ye-Feng , Chen Ru-Shan ,   Department of Communication Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
Published: November 2020

Frequency selective surface (FSS) is of great research interest for its wide applications in radome, absorber, electromagnetic filters, and artificial electromagnetic bandgap materials. In order to achieve a multifunctional FSS with real-time manipulated radar cross-section (RCS), there are mainly three ways, i.e. to design reconfigurable FSS unit cell, reconfigurable screen, and a combination of reconfigurable unit cell and screen. In this work, a combination design of both the reconfigurable unit cells and FSS screen is proposed to realize a dual-band FSS absorber with real-time manipulated RCS. For the reconfigurable unit cell, an angular ring and a meander cross dipole are combined to obtain a dual-band absorption. The dual-band resonance frequencies are reconfigurable by switching the PIN diodes embedded in the unit cell. When switching the PIN diodes, the resonance frequencies of the unit cell would be changed due to the variation of the effective capacitance and inductance of the unit cell. For the reconfigurable FSS screen, a novel biasing network is introduced, then the scattering field from each unit cell is modulated independently by switching the “on/off” state of the PIN diode through using a programmable field programmable gate array (FPGA). The total scattering far field is expressed as the superposition of the scattering field from each unit cell, and the far field scattered by the unit cell which is evaluated under an infinite periodic boundary condition. The scattering field of the FSS absorber can be predicted by considering the working states of all the unit cells on the screen. We define the unit cell as state “0”, when all the PIN diodes are at the states of “off”, and as state “1” when the PIN diodes are all at the states of “off”. The entire screen of FSS absorber is thus pixelated, which can be expressed by a binary coding matrix. The real-time scattering fields from the FSS absorber are manipulated perfectly by optimizing the states matrices showing “on/off” of each unit cell with genetic algorithm (GA). The FSS absorber is fabricated and measured. The ranges of 33dB and 25dB reconfigurable monostatic RCS at 3.2 GHz and 10.3 GHz are achieved by coding the states of unit cells on the FSS absorber screen. Both full-wave and analytical simulations demonstrate the effectiveness of the proposed optimization procedure. Compared with the reported FSS absorber, the proposed design is validated to possess good performance.
Thermal regulation mechanism of photoluminescence in intrinsic acceptor-rich ZnO microtube
Authors: Wang Qiang , Yang Li-Xue , Liu Bei-Yun , Yan Yin-Zhou , Chen Fei , Jiang Yi-Jian ,   Department of Materials Science and Engineering, Beijing Institute of Petrochemical Technology, Beijing 102617, China,   Institute of Laser Engineering, Beijing University of Technology, Beijing 100124, China,   School of Science, Guangxi University of Science and Technology, Liuzhou 545006, China
Published: November 2020

Thermal effect is one of the most important factors limiting the photoluminescence performances of semiconductor devices. With the increase of temperature, the PL intensity decreases gradually due to the effect of thermal quenching. However, the abnormal negative thermal quenching effect has been found in many semiconductor materials in recent years, e.g. ZnO, BiFeO3, InPBi, etc. This effect is generally considered as the sign of the existence for middle/local energy state in the electron-hole recombination process, which usually needs to be confirmed by the temperature-dependent PL spectra.

Here, we report the thermal regulation mechanism of photoluminescence in intrinsic acceptor-rich ZnO (A-ZnO) microtubes grown by the optical vapour supersaturated precipitation method. The grown A-ZnO microtube with a length of 5 mm and diameter of 100 μm has regular hexagonal cross-section morphology. Its optical band gap at room temperature is about 3.30 eV. With the increase of temperature, the PL intensity of A-ZnO microtube exhibits an abnormal behavior from the thermal quenching to the negative thermal quenching and then to the thermal quenching. The thermal quenching effect at 80–200 K is associated with regurgitation/ionization of shallow donor, thermal ionization of free exciton, and conversion of neutral acceptor bound exciton. The negative thermal quenching effect at 200–240 K is associated with thermal excitation of electrons in a deep level trap of 488 meV below the conduction band minimum (CBM). The thermal quenching effect at 240–470 K is related to Shockley-Read-Hall recombination based on the non-radiative recombination center of 628 meV below the CBM. The non-radiative recombination center and trap level are far from the acceptor level of A-ZnO microtube, which may be related to the deep-level defect of oxygen vacancy in the intrinsic A-ZnO microtube. This work establishes the temperature-dependent transition model of photo-generated carriers and reveals the thermal regulation mechanism of PL for the A-ZnO microtubes. It provides a novel platform for designing the high-temperature and high-efficiency ZnO-based photoelectric devices.
INVESTIGATIONS ON A NEW NUCLEAR POTENTIAL
Authors: T. C. Lee  ,   浙江大学物理系
Published: November 2020

The potential between two nucleons suggested by K. C. Wang, viz. V=V(r)=-Aeklr for r≥a, V=V(a) for r<a, is applied to find (1) the wave function of the ground state ot the deuteron by the method of numerical integration, (2) the cross section of the neutron-proton scattering, and (3) the cross-section of the photo-disintegration of the deuteron by γ-rays. The results of calculation or the cross-sections are in fair agreement with the experimental values.
DIFFUSE BANDS IN ABSORPTION AROUND THE SODIUM PRINCIPAL DOUBLETS IN THE PRESENCE OF NITROGEN AND HYDROGEN
Authors: T. S. KE
Published: November 2020

Following the observation of the diffuse absorption bands near the second member of the principal series of Rb and Cs by Ny and Chen in the presence of foreign gases, we were led to study the absorption spectrum of sodium in the presence of nitrogen and hydrogen with a Hilger E-316 quartz spectrograph and a 10-foot grating spectrograph of Eagle mounting. Corrosion resistant MgO windows were used in the absorption tube so that both the absorbing and the perturbing atoms within the absorbing column had a homogeneous concentration. Diffuse absorption band was observed only by the shorter wave-length side of the third member of the principal series but not by any of the others. The separation between the intensity maximum of the diffuse band and the principal lines is larger in the case of hydrogen than that of nitrogen. They are 3.48 A for nitrogen and 4.17 A for hydrogen. The wavelength of the intensity maximum of these bands are respectively 2849.4 A and 2848.7 A for nitrogen and hydrogen.
DISSIPATION FUNCTION OF COMPRESSIBLE FLUIDS
Authors: HOFF LU  ,   浙江大学物理系
Published: November 2020

An expression is given, for the part of dissipation function that is clue to volume viscosity as introduced in our viscocbistic theory. It is shown to be in accordance with the results of our theory of sound absorption. Certain features of this function arc briefly discussed.
NOTE ON VELOCITY TRANSFORMATIONS IN SPECIAL RELATIVITY.
Authors: HSIN P. SOH  ,   浙江大学物理系
Published: November 2020

Three dimensional velocity transformations in special relativity can form quaternion group if each is subject to a further rotation about the direction of the velocity through the same imaginary angle.
A PHOTO-ELECTRONIC FOG COUNTER
Authors: Y. T. WEI  ,   南京大学物理系
Published: November 2020

A photo-electronic fog counter has been developed on the principle of counting flashes of light scattered from individual fog droplets with a photomultiplier. Since a photomultiplier appears to act very rapidly and reponse in a time of the order of 10-8 sec. is possible, the maximum counting rate is limited only by the sealer which is associated with the counter. If a Berkeley Sealer (Model 1000B) is used, this counter is capable of counting fog droplets at a rate of 300,000/min. with very small error and the chance of coincidence countings is therefore small. This counter will prove useful for even very dense fogs or any other kind of aerosols. The optical theory of scattering which may lead to the determination of particle size from size of electric pulse has been introduced.Preliminary experiments show the applicability of this counter for droplet size measurement. There seems to be of no doubt that this counter could register the smallest droplets that occur in natural fogs (i.e., of the order of r≈1 micron) and a better sensitivity can be achieved by reducing stray-light noise level and improving signal to noise ratio. Possibilities of further improvements of the present instrument both as a fog counter and as a droplet size indicator have been discussed.
THE DECAY OF THE NEUTRAL τ0- MESON
Authors: H. Y. TZU  ,   中国科学院近代物理研究所
Published: November 2020

A comparison between the decay phenomena of the neutral τ0 and π0 -mesons is made. The possibilities of the neutral τ0- meson's being a pa rticlek of spin zero or ?,or being a composite particle are discussed.
LARGE DEFLECTION OF A CIRCULAR PLATE WITH A CIRCULAR HOLE AT THE CENTER
Authors: YEH KAI-YUAN  ,   清华大学
Published: November 2020

The equation for the large deflection of thin plates established by Th. von Karman has been well known for many years. But so far there are only a few problems been studied with numerical certainty. S. Levy was the first to apply this equation to solve the problem of a clamped plate under uniform pressure by the method of power series. After this, S. Levy got the solution of the simply supported rectangular plate also under uniform load by the method of double trigonometric series. These two methods used nearly the same procedure of determining the numerical value of the coefficents. But their numerical works are too cumbersome. Lately, W. Z. Chien treated Way's problem again by means of the perturbation method and obtained excellent results.In this paper, the problem of large deflection of a circular plate with a circular hole at the center is treated with the perturbation method.Recently, C. A. AлeKceeB worked out the same problem with the membrance theory, but his results differ greatly from the practical case of a thin plate. The reason of this is chiefly due to his neglecting the effect of bending. The results obtained in this paper are compared with those of AлeKceeв and discussed. We conclude that under concentrated load, the bending effect is momentous and therefore it cannot be neglected. The problem can be extended to other boundary conditions with the maximum deflection YM as parameter.
CONTINUOUS BEAMS WITH NON-UNIFORM STIFFNESS
Authors: CHIEN WEI-ZANG  ,   清华大学
Published: November 2020

In this paper, the method of continued fraction is used for the determination of the bending moments of a continuous beam with non-uniform stiffness.
ON THE DECAY OF TURBULENCE
Authors: CHUANG FENG-KAN  ,   中国科学院数学研究所
Published: November 2020

This paper consists of two parts. The first part gives a description of the motion of large eddies in a turbulent flow. The non-stationary character of the large eddies is emphasized. Up to present, there appears to be some confusion regarding the law of turbulence decay, especially the variation of the microscale with time. This paper introduces a new characteristic length for large eddies which leads to a new decay law valid at the initial period. The apparent discrepancies between Kolmogoroffs decay law and Lin's decay law are seen to be due to different expansions of the present one. It is hoped that the physical picture described herein would give some further insight into the structure of turbulence. In the second part, an analysis similar to that adopted iby Sedov for the correlation coefficients is applied to the turbulent spectrum. New results are obtained, in particular the transition of the decay law from the initial period to the final period.
ORBITAL ANGULAR MOMENTUM DISTRIBUTION IN NUCLEI AND NUCLEAR DENSITY
Authors: YANG LI-MING  ,   北京大学物理系
Published: November 2020

The purpose of this paper is to investigate to what extent the distribution of orbital angular momentum of nucleons in a nucleus implied by the (theory of shell structure limits the form of nuclear density. The effect of the latter has shown itself in a number of physical problems, such as the scattering of high, energy electrons by nuclei, the hyperfine structure, the absorption of negative μ-mesons by nuclei, internal conversion coefficient in heavy elements, etc.
Processing moving visual scenes during upright stance in elderly patients with mild cognitive impairment
Authors: Kucharik Martin , Kosutzka Zuzana , Pucik Jozef , Hajduk Michal , Saling Marian
Published: November 2020

Background

The ability to maintain balance in an upright stance gradually worsens with age and is even more difficult for patients with cognitive disorders. Cognitive impairment plays a probable role in the worsening of stability. The purpose of this study was to expose subjects with mild cognitive impairment (MCI) and healthy, age-matched controls to moving visual scenes in order to examine their postural adaptation abilities.

Methods

We observed postural responses to moving visual stimulation while subjects stood on a force platform. The visual disturbance was created by interposing a moving picture in four directions (forward, backward, right, and left). The pre-stimulus (a static scene for 10 s), stimulus (a dynamic visual scene for 20 seconds) and post-stimulus (a static scene for 20 seconds) periods were evaluated. We separately analyzed the total path (TP) of the center of pressure (COP) and the root mean square (RMS) of the COP displacement in all four directions.

Results

We found differences in the TP of the COP during the post-stimulus period for all stimulus directions except in motion towards the subject (left p = 0.006, right p = 0.004, and away from the subject p = 0.009). Significant RMS differences between groups were also observed during the post-stimulus period in all directions except when directed towards the subject (left p = 0.002, right p = 0.007, and away from the subject p = 0.014).

Conclusion

Exposing subjects to a moving visual scene induced greater destabilization in MCI subjects compared to healthy elderly controls. Surprisingly, the moving visual scene also induced significant aftereffects in the MCI group. Our findings indicate that the MCI group had diminished adaptation to the dynamic visual scene and recovery. These results suggest that even mild cognitive deficits can impair sensory information integration and alter the sensory re-weighing process.
Cultura jurídica chilena, derecho a la identidad cultural y jurisprudencia, un acercamiento metodológico interdisciplinario
Authors: Faundez Peñafiel Juan Jorge , Le Bonniec Fabien
Published: November 2020

Examinamos las transformaciones o conflictos que se presentan en la cultura jurídica chilena, en relación con el derecho a la identidad cultural de pueblos indígenas y otros grupos. Al efecto, la investigación: (i) formula una metodología especializada, interdisciplinaria que comprende el estudio del campo jurídico en su conjunto: contexto, normas constitucionales, las prácticas de los operadores, sus comprensiones y cómo se reflejan en la jurisprudencia; (ii) aplicando dicha metodología, estudia las transformaciones o tensiones que se pueden identificar en la cultura jurídica chilena en relación con el derecho a la identidad cultural.
A Study to Analyse the Knowledge Level of Women Beneficiaries of Anganwadi Centres (AWC) Regarding Nutrition in District Budgam of Kashmir Region
Authors: Ghani Iffat
Published: November 2020

Mother is a main caretaker of their children particularly during the first three to six years of life when they are at the risk of being undernourished. How well she takes care of her children to keep them healthy will depend upon the level of her knowledge regarding childcare and nutrition and various associated factors. As such this study was planned to assess and enhance the extent of knowledge among women beneficiaries of ICDS (Integrated child development Service Scheme) centers of district Budgam of Kashmir region. With an  intension  to surpass  and facilitate the knowledge of women beneficiaries  this study was taken up with a sample  of 600 registered women beneficiaries of AWCs (Anganwadi centers) out of which 150 were nursing mothers, (NM) 150 were pregnant women (PW) and 300 were mothers of child beneficiaries (MCB having children in the age group 6 months-3years. The tool used for assessing the knowledge level was a self-devised rating scale designed to measure the nutritional knowledge related to importance of different kinds (variety) of foods for adequate/ optimal growth and development of a child. Further, in order to divide the levels of nutritional knowledge as, low, medium and high, Quartiles were calculated. In this way the mothers having low level of knowledge (Q1) those who scored up to 4, medium (Q2)  whereas, sample women who scored between 5-6 and high level of knowledge (Q3) scored as ≥ 7.The statements were so arranged that a positive answer was specified under score of 1, whereas, a  negative statement was granted a score of 0 . The scores of positive responses were summed up and the level of knowledge of women beneficiaries was ascertained, a statistically significant variation is observed in levels of nutritional knowledge as per educational qualification and income group among the respondents. It is also seen that respondents from block B.K.Pora and Nagam blocks are having high level of nutritional knowledge in comparison to block Budgam and Chadoora. Among the groups, MCB are having higher level of knowledge in comparison to NM and PW. No significant variation in the levels of nutritional knowledge is seen as per age. It is quite obvious from the study that education of mothers is directly related to knowledge. Educated mother are more knowledgeable than functionally literate mothers.
Adaptation Measures to Mitigate the Impacts of Climate Variability among Pastoralists in Kajiado, Kenya
Authors: Yala Jacktone Achola , Onono Joshua Orungo , Ogara William Okelo , Ouma Gilbert Ongisa , Okuthe Sam Oyieke
Published: November 2020

Climate change and variability has direct and indirect effects on pastoralism through its effect on natural resources including water and pastures that support livestock production in pastoral areas. This study was conducted in Kajiado County where pastoralism is the main source of livelihood. The objective was to identify challenges facing pastoralism and adaptation measures applied by Maasai pastoralists to mitigate impacts of adverse climate events including flooding and drought. A cross-sectional study design was used and primary data collected through focus group discussions (FGDs), key informant interviews (KIIs) and expert opinion interviews (EOIs). A total of 10 FGDs (114 respondents within 10 wards, out of which 81 were men and 33 women), 25 KIIs (6 opinion leaders, 5 village elders, 6 chiefs, 6 government staff and 2 non-governmental organisation) and 12 EOIs (1 Department of Meteorological Services, 1 National Drought Management Authority (NDMA), 2 Department of Agriculture and 8 Departments of Veterinary Services and Livestock Production) were conducted during the data collection period. The findings showed that drought and flooding were the main climate related challenges that were often experienced by the pastoralists. The adaptation measure which were frequently implemented by pastoralist during flooding was livestock vaccination and mass treatment of sick livestock (Z >1.96) while the most frequently implemented adaptation measures during drought periods included migration with livestock to search for water and pasture (Z=1.51) and livestock vaccination and treatment of sick livestock (Z=1.08). Other climate variability related-challenges included increased incidences of livestock diseases, increased livestock deaths, increased cases of community conflicts, unavailability of veterinary vaccines and medicines, high cost of livestock vaccines and drugs and inadequate number of technical staff within the county. The study has shown that climate variability has significant impact on sources of livelihood for pastoralists who in turn are implementing several adaptation measures to mitigate the effects of climate change and variability. The study recommends formulation and implementation of appropriate plans and policies that are focussed on supporting resilience of the vulnerable pastoral communities and that could further assist in fighting the negative impacts of climate change and variability.
Dynamics of the Optical Pulse in a Nonlinear Medium: Approach of Moment Method Coupled with the Fourth Order Runge-Kutta Method
Authors: Koki Fessomon , Edah Gaston , Chichi Minadohona Maxime Capo- , Djossou ´ Gaetan Finagnon , Elloh Camille , Ayela Marc
Published: November 2020

In this paper, we considered the nonlinear Schrodinger equation and applied the moment method ¨ in order to investigate the evolution of pulse parameters in nonlinear medium. This mathematical model described the effects of cubic nonlinear and the nonlinear dispersion terms on the soliton.  The application of the moment method leads to variational equations that is integrated numerically by the fourth order Runge-Kutta method. The results obtained shows the variations of some important parameters of the pulse namely the energy, the pulse position, the frequency shift, the chirp and the width. It reveals the effects of the nonlinear dispersion and nonlinear cubic terms on each parameter on the pulse. The moment method is appropriate to study the dynamics of theoptical pulse in a nonlinear medium modelled by the nonlinear Schrodinger equation.
In vivo actions of protein phosphatase inhibitor‐2 inXenopusoocytes
Authors: Foulkes J.Gordon , Maller James L.
Published: July 2002

Meiotic maturation of amphibian oocytes induced by progesterone is known to be regulated by protein phosphorylation. To investigate a possible role for protein phosphatase‐1 in this process, the effect of phosphatase inhibitor‐2 was determined on the in vivo rate of dephosphorylation of phosphorylaseaand on the rate of oocyte maturation. Dephosphorylation of microinjected phosphorylaseawas inhibited up to 40% in the presence of inhibitor‐2, with half‐maximal inhibition at an intracellular concentration of 0.6 μM. Inhibitor‐2 also caused over a 3‐fold increase in the half‐time for maturation, suggesting a possible role for protein phosphatase‐1 in the regulation of meiosis.
Antigenic sites of the nicotinic acetylcholine receptor cannot be predicted from the hydrophilicity profile
Authors: Juillerat M.A. , Barkas T. , Tzartos S.J.
Published: July 2002

The amino acid sequences of the polypeptide chains of the acetylcholine receptor have recently been published. From the hydrophilicity profiles, it has been proposed that residues 161–166 of the α‐chain might be an important antigenic site. We have synthesised a peptide containing this sequence and raised antisera to it. Here we report that this peptide does not represent an important antigenic site on the molecule, and that this region is probably inaccessible to antibodies. Based on the known DNA sequences and hydrophilicity profiles of the receptor chains, we suggest that many regions of high hydrophilicity may represent inter‐domain regions of proteins.
Synergism between phorbol ester and A23187 in Superoxide production by neutrophils
Authors: Dale M.Maureen , Penfield Adrienne
Published: July 2002

Concentrations of phorbol myristate acetate and the calcium ionophore, A23187, which by themselves are minimally effective in stimulating Superoxide generation in human neutrophils show marked mutual potentiation when given together. This supports the hypothesis that synergism between cytosolic calcium and protein kinase C is involved in the stimulus/activation coupling of the respiratory burst in the neutrophil. Neutrophil
Phorbol ester
Protein kinase C
Calcium
Loss of liposome binding of NADH dehydrogenase from alkalophilic Bacillus on subtilisin digestion
Authors: Xuemin Xu , Hisae Nobuo , Koyama Noriyuki , Nosoh Yoshiaki
Published: July 2002

Alkalophile NADH dehydrogenase consisting of two 65‐kDa subunits was changed by subtilisin into an enzyme species consisting of two 38‐kDa subunits. The amino acid composition and enzyme activity per molecule of the subtilisin‐treated enzyme were almost the same as those of the native enzyme, respectively. On mixing with phospholipid liposome, the conformation of the native enzyme was changed, as suggested by the changes in the type ofArrhenius plot and of CD spectrum and enzyme activity. These conformational properties of the subtilisin‐treated enzyme, on the other hand, were not affected by liposome. Gel filtration of the subtilisin‐treated enzyme mixed with the liposome showed no binding of the protein to liposome.
Guanine nucleotides modulate the ligand binding properties of cell surface folate receptors in Dictyostelium discoideum
Authors: De Wit René J.W. , Bulgakov Roman
Published: July 2002

Dictyostelium discoideum cells show 2 distinct classes of cell surface binding sites for folates. One type is non‐specific, i.e., binds folic acid (FA), 2‐deaminofolic acid (DAFA), and methotrexate (MTX) with similar affinity (K
0.5 ⋍ 140 nM). Scatchard analysis of this non‐specific binding type suggests either heterogeneity or negative cooperativity. Isolated D. discoideum membranes show similar binding characteristics. Guanine nucleotides changed the binding levels of [3H]MTX. In the presence of 0.1 mM GTP, the number of binding sites remains unchanged, while the affinity decreases. GDP and guanylyl imidodiphosphate (GPPNP) are required at about 20‐fold higher concentration than GTP, which elicits a half‐maximal effect at 15μM. Other guanine and adenine nucleotides are ineffective up to 1 mM. These results suggests that the non‐specific cell surface receptor for folic acid interacts with a guanine nucleotide regulatory (G‐) protein.
Multiple isotypes of α‐ and β‐tubulin in the plant Phaseolus vulgaris
Authors: Hussey Patrick J. , Gull Keith
Published: July 2002

The tubulins of the plant Phaseolus vulgaris have been identified in cell extracts by a combination of western blotting of 1D and 2D gels and detection by monoclonal antibodies specific for α‐ and β‐tubulin. Plant α‐tubulin differs from mammalian tubulin in that it migrates ahead of the β‐subunit on Laemmli SDS gels. The Phaseolus root tip extracts contain 4 α‐ and 4 β‐tubulin isotypes which are electrophoretically separable on 2D gels under a number of preparative conditions. The results indicate a complex expression of multiple tubulin isotypes in plant tissues.
Preferential glutamine uptake in rat brain synaptic mitochondria
Authors: Steib A. , Rendon A. , Mark J. , Borg J.
Published: July 2002

Glutamine uptake has been studied in purified rat brain mitochondria of synaptic or non‐synaptic origin. It was taken up by an active saturable transport mechanism, with an affinity two‐times higher in synaptic than in non‐synaptic mitochondria (K
m = 0.45 and 0.94 mM, respectively), V
max of uptake was 7‐times higher in synaptic mitochondria (V
max = 9.2 and 1.3 per mg protein, respectively). Glutamine transport was found to be inhibited by L‐glutamate (IC50 = 0.64 mM) as well as thiol reagents (mersalyl, N‐ethylmaleimide). It is suggested that differential uptake of glutamine in mitochondria of synaptic or nonsynaptic origin may be a major mechanism in the regulation of the synthesis of the neurotransmitter glutamate.
Crystallization of the bifunctional proteinase/amylase inhibitor PKI‐3 and of its complex with proteinase K
Authors: Pal Gour P. , Betzel Christian , Jany Klaus-Dieter , Saenger Wolfram
Published: July 2002

One of the three wheat germ inhibitors of proteinase K is bifunctional and inhibits simultaneously proteinase K (or subtilisin but not enzymes of the trypsin family) and insect α‐amylase. The molecular mass of this inhibitor called PKI‐3 is 21 kDa, and the binding constant for proteinase K is 0.8 nM at pH 8.2, 25°C, in 1:1 molar ratio. PKI‐3 was crystallized by microdialysis against 10–12% polyethylene glycol 6000, 50 mM NaH2PO4, pH 6.7. The crystals have monoclinic space group P21 with a = 42.5, b = 65.3, c = 31.5 Å, β = 110°, and diffract beyond 2.0 Å resolution. The complex proteinase K · PKI‐3 was crystallized by equilibrium vapor diffusion under the same conditions. The crystals are needle‐shaped and still too small for X‐ray analysis. Gel electrophoresis established the composition of the crystals.
Synthesis of seven different homologous phytochelatins in metal‐exposed Schizosaccharomyces pombe cells
Authors: Grill E. , Winnacker E.-L. , Zenk M.H.
Published: July 2002

The family of heavy metal‐sequestering peptides with the formula (γ‐Glu‐Cys)
n
Gly; n = 2–8), the phytochelatins (PCs), are not restricted to higher plants. In Schizosaccharomyces pombe the occurrence of two of these peptides has previously been reported. Reinvestigation of the peptide pattern of the heavy metal‐exposed fission yeast led to the discovery of five additional peptides, a pattern which now corresponds qualitatively exactly to the one in higher plants. From the kinetics of induction we propose that PCs are synthesized by consumption of glutathione or its biosynthetic precursor.
Destabilization of actin filaments as a requirement for the secretion of catecholamines from permeabilized chromaffin cells
Authors: Lelkes Peter I. , Friedman Jonathan E. , Rosenheck Kurt , Oplatka Avraham
Published: July 2002

In the search for a functional role of cytoskeletal proteins in the mechanism(s) of stimulus‐secretion coupling, we have previously demonstrated that the actomyosin system might be involved in the transport of cations across the plasma membrane of bovine adrenal chromaffin cells [(1986) J. Biol. Chem. 261, 5745‐5750]. To establish whether actin and myosin might also be involved in later stages of the cellular response, we have examined the possible effects of various actin‐specific reagents on the calcium‐mediated secretion of catecholamines from digitonin‐permeabilized cells. F‐Actin‐destabilizing agents, such as cytochalasin D or DNase 1, were found to promote Ca2+‐stimulated (as well as basal) secretion. By contrast, stabilizers, like phalloidin, produced the opposite effect. It is concluded that stimulus‐secretion coupling in chromaffin cells might require the reorganization of actin for modulating both ion transport across the plasma membrane and exocytotic secretion per se.
All four internally repetitive domains of pig calpastatin possess inhibitory activities against calpains I and II
Authors: Maki Masatoshi , Takano Emiko , Mori Hirotaka , Sato Akihiko , Murachi Takashi , Hatanaka Masakazu
Published: July 2002

Complementary DNA portions coding for each domain (domain L internally repetitive domains, domains 1–4, each composed of approximately 140 amino acid residues) of pig calpastatin were subcloned into E. coli plasmids to express the respective portions of the proteinase inhibitor gene in bacteria. Cell extracts of E. coli harboring recombinant plasmids were assayed for calpain inhibition. All four internally repetitive domains showed inhibitory activities, essentially similar to one another, against calpains I and II. No inhibition was observed in the case of the N‐terminal non‐homologous domain (domain L). These results support our previous conclusion that the repetitive region is a functional unit of the proteinase inhibitor.
Crosslinking between the 33 kDa extrinsic protein and the 47 kDa chlorophyll‐carrying protein of the PS II reaction center core complex
Authors: Enami Isao , Satoh Kazuhiko , Katoh Sakae
Published: July 2002

Using highly purified oxygen‐evolving photosystem II complexes from spinach, the 33 kDa extrinsic protein was found to crosslink with the 47 kDa chlorophyll‐carrying protein with a cleavable bifunctional crosslinking reagent, dithiobis(succinimidylpropionate).
The sequence of human retinal S‐antigen reveals similarities with α‐transducin
Authors: Yamaki Kunihiko , Tsuda Masahiko , Shinohara Toshimichi
Published: July 2002

The complete amino acid sequence of human retinal S‐antigen (48 kDa protein), a retinal protein involved in the visual process has been determined by cDNA sequencing. The largest cDNA was 1590 base pairs (bp) and it contained an entire coding sequence. The similarity of nucleotide sequence between the human and bovine is approximately 80%. The predicted amino acid sequence indicates that human S‐antigen has 405 residues and its molecular mass is 45050 Da. The amino acid sequence homology between human and bovine is 81%. There is no overall sequence similarity between S‐antigen and other proteins listed in the National Biomedical Research Foundation (NBRF) protein data base. However, local regions of sequence homology with α‐transducin (Tα) are apparent including the putative rhodopsin binding and phosphoryl binding sites. In addition, human S‐antigen has sequences identical to bovine uveitopathogenic sites, indicating that some types of human uveitis may in part be related to the animal model of experimental autoimmune uveitis (EAU).
Hormone synthesis in human thyroglobulin: Possible cleavage of the polypeptide chain at the tyrosine donor site
Authors: Marriq Claudine , Lejeune Pierre-Jean , Venot Nicole , Vinet Liliane
Published: July 2002

At moderate iodination levels (20 iodine atoms/mol) human thyroglobulin (hTg) produces after reduction a hormone‐rich peptide of 26 kDa which contains the preferential hormonogenic ‘acceptor’ tyrosine (Tyr 5) of the protein. The site of cleavage of the hTg chain was demonstrated by analysis of the 26 kDa tryptic hydrolysis products. It consistently yielded the peptide Gln‐82—Val‐129 which consequently made it possible to localize the hTg chain cleavage at tyrosine residue 130. Evidence for tyrosine involvement in hTg cleavage during thyroid hormone formation supports the hypothesis that peptide bond cleavage would occur at the ‘donor’ tyrosine residue and suggests that tyrosine 130 would be the donor site reacting with the major hormone‐forming acceptor site (Tyr 5) of hTg.
Interaction of antibodies to synthetic peptides of proNGF with in vitro synthesized NGF precursors
Authors: Dicou Eleni
Published: July 2002

Sera raised against three synthetic peptides that reproduce sequences of the pro‐nerve growth factor (proNGF) protein were tested in immunoprecipitation experiments using in vitro translation products of SP6‐directed NGF mRNA in a rabbit reticulocyte lysate. The interaction of these antibodies with bacterially synthesized chimeric preproNGF was also examined. Digestion of the translation products by the γ‐subunit generated the 22 and 18 kDa intermediates. A predominant 13 kDa intermediate was obtained after digestion of translation products in wheat germ extract. This is shown to be the N‐terminal peptide by immunoprecipitation with an anti‐peptide serum. These antibodies may be used to detect NGF precursor cleavage products in vivo.
Immunocytochemical evidence for the acidic nature of peroxisomes in methylotrophic yeasts
Authors: Waterham Hans R. , Keizer-Gunnink Ineke , Goodman Joel M. , Harder Wim , Veenhuis Marten
Published: July 2002

The possible acidic nature of the peroxisomal matrix present in intact yeast cells was studied immunocytochemically, using the weak base DAMP as a probe. Spheroplasts of methanol‐grown Candida boidinii and Hansenula polymorpha were regenerated and incubated with DAMP. After immunogold labelling, using antibodies against DAMP, a specific accumulation of gold particles was observed on the peroxisomal profiles. This labelling was absent in controls, performed in the presence of ionophores or chloroquine. These results support earlier observations, that in intact cells a pH‐gradient exists across the peroxisomal membrane. Experiments, carried out on osmotically swollen spheroplasts indicated that maintenance of this pH‐gradient is strongly related to the cell's integrity.
Newly identified type of β actin reduces invasiveness of mouse B16‐melanoma
Authors: Sadano Hiroyuki , Taniguchi Shun'ichiro , Baba Tsuneo
Published: July 2002

Low metastatic parent B16 melanoma and isolated B16‐F1 cell lines have a third actin designated as βm(Ax:previously). ßm actin is scantily or not at all detected in highly metastatic cell lines, such as B16‐F10 and BL6. To directly assess the physiological role of ßm in phenotypic changes of B16 melanoma, we transfected expression plasmids of βm into B16‐F10 cells. The actin expressed in the transfectants is located largely in cytoskeletal fractios. The transfectants exhibited a larger number of stress fibers and a lower invasiveness than did the recipient cells. Thus, βm actin plays an important role in the organization of actin stress fibers, the result being a decrease in invasiveness of B16 melanoma.
The heavy chain of tetanus toxin can mediate the entry of cytotoxic gelonin into intact cells
Authors: Johnstone Stephen R. , Morrice Lora M. , van Heyningen Simon
Published: July 2002

An artificial conjugate of the heavy chain of tetanus toxin linked by a disulphide bond to the impermeant ribosome‐inactivating protein gelonin is cytotoxic to intact HT29 cells by inhibiting intracellular protein synthesis. Neither toxin nor gelonin alone has any significant effect. This shows that the heavy chain has the ability to mediate internalization of a protein to which it is bound by a disulphide bond. Thus the normal role of the tetanus toxin heavy chain may be to allow entry of the light chain into a cell.
High activity of inclusion bodies formed in Escherichia coli overproducing Clostridium thermocellum endoglucanase D
Authors: Tokatlidis Kostas , Dhurjati Prasad , Millet Jacqueline , Béguin Pierre , Aubert Jean-Paul
Published: July 2002

The formation of cytoplasmic inclusion bodies by Escherichia coli overproducing Clostridium thermocellum endoglucanase D (EGD) was investigated. EGD was found in inclusion bodies as a 68 kDa form, whereas the size of the cytoplasmic form was 65 kDa. Upon solubilization with urea followed by dialysis, the 68 kDa form was converted to the 65 kDa species. Proteolysis occurred within the COOH‐terminal, reiterated region of the 68 kDa form, which is conserved among most C. thermocellum endoglucanase, but is not required for catalytic activity. The specific activity of the enzyme embedded in inclusion bodies was close to that of the purified protein. Thus, inclusion body formation does not involve denaturation of the catalytic domain of EGD, but more likely, the participation of the reiterated, conserved region in intermolecular interactions.
Destabilization of Zn2+ coordination in ADP‐ribose transferase (polymerizing) by 6‐nitroso‐1,2‐benzopyrone coincidental with inactivation of the polymerase but not the DNA binding function
Authors: Buki Kalman G. , Bauer Pal I. , Mendeleyev Jerome , Hakam Alaeddin , Kun Ernest
Published: July 2002

6‐Nitroso‐ 1,2‐benzopyrone, an oxidation product of 6‐amino‐ 1,2‐benzopyrone, binds to the DNA‐recognizing domain of the ADP‐ribose transferase protein and preferentially destabilizes Zn2+ from one of the two zinc finger polypeptide complexes present in the intact enzyme, as determined by the loss of 50% of 65Zn2+ from the 65Zn2+‐isolated protein molecule, coincidental with the loss of 99% of enzymatic activity. The 50% zinc‐deficient enzyme still binds to a DNA template. consisting of a 17‐mer DNA primer annealed to M 13 positive strand, resulting in the blocking of DNA synthesis by the Klenow fragment of Pol I, Auto‐poly‐ADP‐ribosylated ADP‐ribose transferase, which is the probable physiological state of this protein in intact cells, does not bind to primer‐template DNA and does not block DNA synthesis by the Klenow fragment. On the basis of this in vitro model it is proposed that molecules which inhibit or inactivate ADP‐ribose transferase in intact cells can induce significant alteration in DNA structure and replication.
Molecular cloning of an essential yeast gene encoding a proteasomal subunit
Authors: Georgatsou Elena , Georgakopoulos Tassos , Thireos George
Published: July 2002

We present the cloning and sequence of a Saccharomyces cerevisiae gene, PUP2, which encodes for a proteasomal subunit. The PUP2 protein is similar to other proteasomal components from yeast, as well as from Drosophila and rat. Although not‐properly‐folded proteins have been implicated to constitute substrates of proteasomes, we show that the accumulation of such proteins does not induce expression of the PUP2 gene. Finally, gene disruption experiments demonstrate that PUP2 belongs to the class of yeast proteasomal subunits that are essential for cell viability.
Nucleotide sequence of the Staphylococcus aureus signal peptidase II (lsp) gene
Authors: Zhao Xiao-Jiong , Wu Henry C.
Published: July 2002

The lsp gene encoding prolipoprotein signal peptidase (signal peptidase II) of Staphylococcus aureus was cloned by screening a genomic library for plasmid clones capable of complementing a conditionally lethal lsp allele of Escherichia coli, E. coli cells carrying one of five overlapping clones exhibited increased resistance to globomycin. The nucleotide sequence of the S. aureus lsp gene was determined. The deduced amino acid sequence of the signal peptidase II of S. aureus suggests that this enzyme has a hydropathy profile very similar to those of E. coli, Enterobacter aerogenes and Pseudomonas fluorescens. Comparison of the primary structures of this enzyme from these four distinct bacterial species reveals three highly conserved domains in proteins which have a low degree of overall sequence homology. Unlike the lsp genes from the Gram‐negative bacteria, the lsp gene in S. aureus is not flanked by x‐ileS and orf149‐orf316 as found in E. coli, Ent. aerogenes, and P. fluorescens.
Heat shock proteins of barley mitochondria and chloroplasts Identification of organellar hsp 10 and 12: putative chaperonin 10 homologues
Authors: Hartman Dallas J. , Dougan David , Hoogenraad Nicholas J. , Høj Peter B.
Published: July 2002

Tissue slices from barley seedlings were subjected to heat shock and metabolically labelled with [35S]methionine and [35S]lcysteine, Mitochondria and chloroplasts were isolated and shown to contain two novel heat shock proteins of 10 and 12 kDa, respectively. The possibility that these proteins, like a mitochondrial 10 kDa stress protein recently isolated from rat hepatoma cells [(1992) Proc. Natl. Acad. Sci. 89, in press] represent eukaryotic chaperonin 10 homologues is discussed.