D-erythroascorbic acid: Its preparations, chemistry, and metabolism (fungi and plants)

The origin of oxalate in plants has received considerable attention and glycolate metabolism has been generally regarded as a prime precursor candidate although studies on the metabolism of L-ascorbic acid single out that plant constituent as well. Experiments with oxalate-accumulating plants that contain little or no tartaric acid revealed the presence of a comparable L-ascorbic acid metabolism with the exception that the cleavage products were oxalic acid and L-threonic acid or products of L-threonic acid metabolism. A reasonable mechanism for cleavage of L-ascorbic acid at the endiolic bond is found in studies on the photooxygenation of L-ascorbic acid. Presumably, analogs of L-ascorbic acid that differ only in the substituent at C4 also form a hydroperoxide in the presence of alkaline hydrogen peroxide and subsequently yield oxalic acid and the corresponding aldonic acid or its lactone. We became interested in such a possibility when we discovered that L-ascorbic acid was rare or absent in certain yeasts and fungi whereas a L-ascorbic acid analog, D-glycero-pent-2-enono- 1,4-lactone (D-erythroascorbic acid), was present. It has long been known that oxalate occurs in yeasts and fungi and its production plays a role in plant pathogenesis. As to the biosynthetic origin of fungal oxalic acid there is little information although it is generally assumed that oxaloacetate or possibly, glycolate, might be that precursor

Zur Spektroskopie des 1ssigma-Orbitals in superschweren Stosssystemen Messungen der Emissionswahrscheinlichkeiten fuer die quasi-molekulare K-Strahlung am Stosssystem Pb + Pb bei kleinen internuklearen Abstaenden

SIGLEDEGerman

High-velocity limit for the ratio of helium double-to-single ionization for highly-charged, bare-ion impact

The ratio R of helium double-to-single ionization cross sections was measured for Ne"1"0"+- and Ni"2"8"+-projectiles at velocities of 0.39#<=#v_P/c#<=#0.93 intending to explore the high-velocity limit of R for highly-charged ion impact. For Ne"1"0"+-projectiles R was observed to become independent of v_P for v_P/c >or#approx# 0.73 and an asymptotic experimental value R=(2.57#+-#0.10).10"-"3 has been established. This is in good agreement with experimental results for proton, antiproton, electron and positron impact and in excellent accordance with the theoretical prediction of (2.59#+-#0.03).10"-"3. (orig.)SIGLEAvailable from TIB Hannover: RO 801(93-66) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Deviation from first order perturbation theory observed at intermediate relativistic velocities for the ionization of highly-charged heavy projectiles

SIGLEAvailable from TIB Hannover: RO801(93-11) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Cold target recoil ion momentum spectroscopy

The experimental technique of Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) is described. It allows a three dimensional imaging of momentum space of the recoiling ion for all ionizing atomic reaction with 4#pi# solid angle for momentum measurement. The resolution presently achieved is #+-#0.035 a.u. Depending on the collision system this corresponds to a resolution in projectile energy loss of down to #DELTA#E/E=10"-"9 and a scattering angle resolution of down to 10"-"9 rad for fast heavy ion collisions. We discuss the experimental technique and some recent results on dynamics of recoil ion production for electron capture, target ionization and projectile electron loss. (orig.)24 refs.Available from TIB Hannover: RO 801(95-80) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Strong directional out-of-plane scattering in multiple ionizing highly charged ion-atom collisions

The azimuthal ([phi][sub r]) and polar angle ([theta][sub r]) scattering of projectiles in coincidence with recoil ions has been studied for 0.53 MeV/u F[sup 8+] + Ne. For high degree of ionization of the target we find the resultant transverse momentum of all electrons emitted into the continuum to increase with the number of ejected electrons and to have a direction mostly not co-planar with the scattering plane

Intra-atomic double scattering of binary encounter electrons in collisions of fast heavy-ions with atoms and molecules

We present first experimental evidence for intra-atomic double scattering of Binary Encounter electrons produced in collisions of 5.9 MeV/u U"2"9"+ with neon, xenon and molecular gases. A broad distribution of electrons is observed at a velocity twice the velocity of the moving ion (v_P) at angles #theta#_e up to 135 . We attribute the emission pattern to well known target Binary Encounter electrons around 2v_P at extreme forward laboratory angles, that are subsequently elastically scattered in the target nuclear potential to the large angles observed. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Detailed investigations of two-center collision dynamics

The combination of recoil ion and ionized electron momentum spectroscopy provides an unparalleled method to investigate the details of ion-atom collision dynamics. In order to predict scattering behavior and collaborate with experimental projects, the classical trajectory 3- and n-body Monte Carlo method has been modified to yield complete momenta information for ionized electron spectra in the collision plane defined by the incident projectile and outgoing projectile or recoil ion. To illuminate the richness of these spectra, calculations of 300 and 500 keV p and p- single ionization collisions with He are presented for low q/v perturbation strengths. For strong q/v collisions, the 100, 300 and 500 keV/u Ne"1"0"+ on He systems are illustrated. Strong asymmetry of the slow and saddle point electrons are predicted for antiproton and highly-charged Ne"1"0"+ projectiles. Furthermore, The electron capture to the continuum spectra for Ne"1"0"+ are observed to have not only the expected asymmetry in the longitudinal direction, but also a strong asymmetry in the collision plane. (orig.)Available from TIB Hannover: RO 801(96-39) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Ratio of cross sections for double to single ionization of He by 85-400 eV photons

The ratio of double to single ionization of He by 85-400 eV photons has been measured using Cold Target Recoil Ion Momentum Spectroscopy. This technique allows the elimination of all possible systematical errors discussed so far in the literature of this subject. We find the ratio in this energy range to be about 25% lower than previously assumed. (orig.)33 refs.Available from TIB Hannover: RO 801(95-79) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman