Chemical signatures for superheavy elementary particles

Models of unified fundamental interactions suggest the existence of many particles in the mass range 10 x 10(9) to 100 x 10(12) electron volts. Among these may be charged particles, X(+/-), that are stable or nearly so. The X(+,)s would form superheavy hydrogen, while the X(-,)s would bind to nuclei. Chemical isolation of naturally occurring technetium, promethium, actinium, protactinium, neptunium, or americium would indicate the presence of superheavy particles in the forms RuX(-), SmX(-), (232)ThX(-), (235,236,238)UX(-), (244)PuX(-), or (247)CmX(-). Other substances worth searching for include superheavy elements with the chemical properties of boron, fluorine, manganese, beryllium, scandium, vanadium, lithium, neon, and thallium.     

Giant radioactive halos: indicators of unknown radioactivity?

A new group of giant radioactive halos has been found with radii in excess of anything previously discovered. Since alternate explanations for these giant halos are inconclusive at present, the possibility is considered that they originate with unknown alpha radioactivity, either from isomers of known elements or from superheavy elements.     

Superheavy elements: an early solar system upper limit for elements 107 to 110

The abundance of samarium-152 in the Santa Clara iron meteorite is found to be 108 x 10(7) atoms per gram. This quantity, if attributed to fission of a superheavy element with atomic number 107 to 109, limits the amount of superheavy elements in the early solar system to 1.7 x 10(-5) times the abundance of uranium-238. For element 110, the limit is 3.4 x 10(-5).     

Ammonia channel couples glutaminase with transamidase reactions in GatCAB

The formation of glutaminyl transfer RNA (Gln-tRNA(Gln)) differs among the three domains of life. Most bacteria employ an indirect pathway to produce Gln-tRNA(Gln) by a heterotrimeric glutamine amidotransferase CAB (GatCAB) that acts on the misacylated Glu-tRNA(Gln). Here, we describe a series of crystal structures of intact GatCAB from Staphylococcus aureus in the apo form and in the complexes with glutamine, asparagine, Mn2+, and adenosine triphosphate analog. Two identified catalytic centers for the glutaminase and transamidase reactions are markedly distant but connected by a hydrophilic ammonia channel 30 A in length. Further, we show that the first U-A base pair in the acceptor stem and the D loop of tRNA(Gln) serve as identity elements essential for discrimination by GatCAB and propose a complete model for the overall concerted reactions to synthesize Gln-tRNA(Gln).     

Direct mapping of nuclear shell effects in the heaviest elements

Quantum-mechanical shell effects are expected to strongly enhance nuclear binding on an "island of stability" of superheavy elements. The predicted center at proton number Z = 114, 120, or 126 and neutron number N = 184 has been substantiated by the recent synthesis of new elements up to Z = 118. However, the location of the center and the extension of the island of stability remain vague. High-precision mass spectrometry allows the direct measurement of nuclear binding energies and thus the determination of the strength of shell effects. Here, we present such measurements for nobelium and lawrencium isotopes, which also pin down the deformed shell gap at N = 152.     

Elements 112 to 119: were they present in meteorites?

Chondrites contain a small fission xenon component of unexplained origin. Evidence on the geochemical behavior of this component suggests that it was not derived from an actinide element (Z = 89 to 103), or from a transition metal between Z = 104 and 111, but from a more volatile progenitor. The most likely candidates are the superheavy elements between Z = 112 and 119, whose lighter congeners (mercury, tellurium, lead, and the like) are known to be strongly fractionated in meteorites.     

Exinct superheavy element in meteorites: attempted characterization

If the unexplained fission xenon component in meteorites is due to a volatile superheavy element, this element must have had a heat of vaporization of 54 +/- 3 kilocalories per mole and a normal boiling point of 2500 degrees +/- 400 degrees K. The prime candidates are elements 111 and 115, followed by 113, 114, 112, and 116. Elements 105 to 110 are not volatile enough and can therefore be excluded.     

Search for interstellar superheavy hydrogen

Models for fundamental physical interactions allow for the existence of stable or nearly stable elementary particles much heavier than the proton. Stellar spectra were searched for a positively charged superheavy particle, X(+), which, with a bound electron, should appear as apparently superheavy neutral hydrogen in the interstellar medium. An upper limit for the abundance of X relative to normal hydrogen in the line of sight toward the bright star gamma Cassiopeiae is 2 x 10(-8).     

The ancient lunar core dynamo

Lunar paleomagnetism provides evidence for the existence of an ancient lunar magnetic field generated in an iron core. Paleointensity experiments give a surface field of 1.3 gauss, 4.0 x 10(9) years ago, subsequently decreasing exponentially. Thermodynamic arguments give a minimum value of the heat source in the core at that time: known sources, radioactive and other, are quantitatively implausible, and it is suggested that superheavy elements were present in the early moon.     

SNARE function analyzed in synaptobrevin/VAMP knockout mice

SNAREs (soluble NSF-attachment protein receptors) are generally acknowledged as central components of membrane fusion reactions, but their precise function has remained enigmatic. Competing hypotheses suggest roles for SNAREs in mediating the specificity of fusion, catalyzing fusion, or actually executing fusion. We generated knockout mice lacking synaptobrevin/VAMP 2, the vesicular SNARE protein responsible for synaptic vesicle fusion in forebrain synapses, to make use of the exquisite temporal resolution of electrophysiology in measuring fusion. In the absence of synaptobrevin 2, spontaneous synaptic vesicle fusion and fusion induced by hypertonic sucrose were decreased approximately 10-fold, but fast Ca2+-triggered fusion was decreased more than 100-fold. Thus, synaptobrevin 2 may function in catalyzing fusion reactions and stabilizing fusion intermediates but is not absolutely required for synaptic fusion.     

食品中残留喹乙醇人工抗原的制备与鉴定

[目的]合成喹乙醇人工抗原。[方法]通过化学合成方法,将喹乙醇与琥珀酸酐反应,合成半抗原喹乙醇半琥珀酸酯(OLA-HS),通过活泼酯化法将半抗原与载体蛋白偶联制备喹乙醇全抗原。[结果]TLC、紫外光谱法的鉴定结果表明,目标半抗原合成成功;紫外光谱法鉴定结果表明,全抗原合成成功。[结论]建立了一种喹乙醇半抗原及全抗原的合成方法,为进一步制备喹乙醇抗体奠定基础。     

Biosynthesis of plant volatiles: nature's diversity and ingenuity

Plant volatiles (PVs) are lipophilic molecules with high vapor pressure that serve various ecological roles. The synthesis of PVs involves the removal of hydrophilic moieties and oxidation/hydroxylation, reduction, methylation, and acylation reactions. Some PV biosynthetic enzymes produce multiple products from a single substrate or act on multiple substrates. Genes for PV biosynthesis evolve by duplication of genes that direct other aspects of plant metabolism; these duplicated genes then diverge from each other over time. Changes in the preferred substrate or resultant product of PV enzymes may occur through minimal changes of critical residues. Convergent evolution is often responsible for the ability of distally related species to synthesize the same volatile.     

Creating a protein-based element of inheritance

Proteins capable of self-perpetuating changes in conformation and function (known as prions) can serve as genetic elements. To test whether novel prions could be created by recombinant methods, a yeast prion determinant was fused to the rat glucocorticoid receptor. The fusion protein existed in different heritable functional states, switched between states at a low spontaneous rate, and could be induced to switch by experimental manipulations. The complete change in phenotype achieved by transferring a prion determinant from one protein to another confirms the protein-only nature of prion inheritance and establishes a mechanism for engineering heritable changes in phenotype that should be broadly applicable.     

重氮化法合成全抗原的研究

[目的]制备氯霉素全抗原,探索氯霉素合成的方法,为动物免疫试验作准备。[方法]采用重氮化法合成氯霉素卵清蛋白全抗原,通过紫外法和红外光谱法测定合成的偶联效果。[结果]重氮化法可用于制备较高偶联率的氯霉素全抗原,用于免疫动物制备抗体。[结论]该研究为合成高效价的抗体奠定了基础。     

X-rays from Coalescing Atoms

The discovery and investigation of X-ray continua has provided a new tool for studying the detailed electronic processes that occur when atoms collide. In the collisions considered here, the quasimolecular origin of the continuum radiation has been established. Therefore, as the atomic numbers of the projectiles and target atoms are increased one can simulate some of the properties of superheavy atoms. In particular, the peaked nature of the x-ray energy dependence of the anisotropy of K, L, and M MO radiation, as well as the peaked nature of the M MO spectra, will allow approximate spectroscopic studies of superheavy atoms. Special excitement attaches to the possibility of observing fundamental processes occurring under extremely high electric and magnetic fields. The recent successful development of a 1400-Mev U beam at the GSI (Gesellschaft für Schwerionenforschung) accelerator in Darmstadt, Germany, promises an imminent attack on these basic problems (63).     

有机合成在农药中的应用

根据有机反应类型和机理把常用化学农药的合成反应大体上分为5类:取代反应、加成反应、重排反应、氧化反应、偶联反应;简要介绍了10种熟悉的农药产品及其合成过程,根据合成过程进行分类并具体分析5类反应在常用化学农药中的应用。     

The cultural background of the sustainability of the traditional farming system in the Ghouta the oasis of Damascus, Syria

This paper discusses thepractical impact of a non-materialistic cultureon sustainable farm management.Two elements are discussed: first, how deeplyrooted religion is in this culture; second,the feasibility of using both human knowledgeand experience, so-called tradition and divineguidance in management. Finally, theimplications of the fusion of these twoelements are drawn. The outcome is thecapability of man to integrate ethical valuesinto decisions and actions. This integration,when applied by skilled farmers, leads to amanagement of natural resources in analtruistic fashion and not merely to economicends. Moreover, it makes agriculture meaningfuland sustainable.