Role of the Binding Energy on Nondipole Effects in Single-Photon Ionization.

We experimentally study the influence of the binding energy on nondipole effects in K-shell single-photon ionization of atoms at high photon energies. We find that for each ionization event, as expected by momentum conservation, the photon momentum is transferred almost fully to the recoiling ion. The momentum distribution of the electrons becomes asymmetrically deformed along the photon propagation direction with a mean value of 8/(5c)(E_{γ}-I_{P}) confirming an almost 100 year old prediction by Sommerfeld and Schur [Ann. Phys. (N.Y.) 396, 409 (1930)10.1002/andp.19303960402]. The emission direction of the photoions results from competition between the forward-directed photon momentum and the backward-directed recoil imparted by the photoelectron. Which of the two counteracting effects prevails depends on the binding energy of the emitted electron. As an example, we show that at 20 keV photon energy, Ne^{+} and Ar^{+} photoions are pushed backward towards the radiation source, while Kr^{+} photoions are emitted forward along the light propagation direction.

High-energy molecular-frame photoelectron angular distributions: a molecular bond-length ruler.

We present a study on molecular-frame photoelectron angular distributions (MFPADs) of small molecules using circularly polarized synchrotron light. We find that the main forward-scattering peaks of the MFPADs are slightly tilted with respect to the molecular axis. This tilt angle is directly connected to the molecular bond length by a simple, universal formula. We apply the derived formula to several examples of MFPADs of C 1s and O 1s photoelectrons of CO, which have been measured experimentally or obtained by means of ab initio modeling. In addition, we discuss the influence of the back-scattering contribution that is superimposed over the analyzed forward-scattering peak in the case of homo-nuclear diatomic molecules such as N2.

Observation of Nondipole-Induced Asymmetry in the Angular Emission Distribution of Photoelectrons from Fixed-in-Space CO Molecules.

We investigate experimentally and theoretically the C and O 1s photoionization of fixed-in-space CO molecules at a photon energy of 905 eV. We find a significant dependence of the photoelectron angular distributions on the direction of propagation of the ionizing radiation. It results from an interplay of nondipole effects, on one hand, and molecular effects, on the other. The nondipole effects lead to an increase of the emission probability in the forward direction along the light propagation, and the photoelectron wave being scattered by the molecular potential gives rise to a strong peak in the direction of the atom neighboring the emitter site. These effects can either conspire or extenuate each other, depending on the photoelectron emission direction and molecular orientation in space.

Ion and Electron Momentum Distributions from Single and Double Ionization of Helium Induced by Compton Scattering.

We present the momentum distributions of the nucleus and of the electrons from double ionization of the helium atom by Compton scattering of photons with hν=40 keV. We find that the doubly charged ion momentum distribution is very close to the Compton profile of the nucleus in the ground state of the helium atom, and the momentum distribution of the singly charged ion to give a precise image of the electron Compton profile. To reproduce these results, nonrelativistic calculations require the use of highly correlated initial- and final-state wave functions.

Investigating charge-up and fragmentation dynamics of oxygen molecules after interaction with strong X-ray free-electron laser pulses.

During the last decade, X-ray free-electron lasers (XFELs) have enabled the study of light-matter interaction under extreme conditions. Atoms which are subject to XFEL radiation are charged by a complex interplay of (several subsequent) photoionization events and electronic decay processes within a few femtoseconds. The interaction with molecules is even more intriguing, since intricate nuclear dynamics occur as the molecules start to dissociate during the charge-up process. Here, we demonstrate that by analyzing photoelectron angular emission distributions and kinetic energy release of charge states of ionic molecular fragments, we can obtain a detailed understanding of the charge-up and fragmentation dynamics. Our novel approach allows for gathering such information without the need of complex ab initio modeling. As an example, we provide a detailed view on the processes happening on a femtosecond time scale in oxygen molecules exposed to intense XFEL pulses.

Fourfold Differential Photoelectron Circular Dichroism.

We report on a joint experimental and theoretical study of photoelectron circular dichroism (PECD) in methyloxirane. By detecting O 1s photoelectrons in coincidence with fragment ions, we deduce the molecule's orientation and photoelectron emission direction in the laboratory frame. Thereby, we retrieve a fourfold differential PECD clearly beyond 50%. This strong chiral asymmetry is reproduced by ab initio electronic structure calculations. Providing such a pronounced contrast makes PECD of fixed-in-space chiral molecules an even more sensitive tool for chiral recognition in the gas phase.

Photon-Momentum-Induced Molecular Dynamics in Photoionization of N_{2} at hν=40 keV.

We investigate K-shell ionization of N_{2} at 40 keV photon energy. Using a cold target recoil ion momentum spectroscopy reaction microscope, we determine the vector momenta of the photoelectron, the Auger electron, and both N^{+} fragments. These fully differential data show that the dissociation process of the N_{2}^{2+} ion is significantly modified not only by the recoil momentum of the photoelectron but also by the photon momentum and the momentum of the emitted Auger electron. We find that the recoil energy introduced by the photon and the photoelectron momentum is partitioned with a ratio of approximately 30∶70 between the Auger electron and fragment ion kinetic energies, respectively. We also observe that the photon momentum induces an additional rotation of the molecular ion.

Recoil-Induced Asymmetry of Nondipole Molecular Frame Photoelectron Angular Distributions in the Hard X-ray Regime.

We investigate angular emission distributions of the 1s photoelectrons of N_{2} ionized by linearly polarized synchrotron radiation at hν=40 keV. As expected, nondipole contributions cause a very strong forward-backward asymmetry in the measured emission distributions. In addition, we observe an unexpected asymmetry with respect to the polarization direction, which depends on the direction of the molecular fragmentation. In particular, photoelectrons are predominantly emitted in the direction of the forward nitrogen atom. This observation cannot be explained via asymmetries introduced by the initial bound and final continuum electronic states of the oriented molecule. The present simulations assign this asymmetry to a novel nontrivial effect of the recoil imposed to the nuclei by the fast photoelectrons and high-energy photons, which results in a propensity for the ions to break up along the axis of the recoil momentum. The results are of particular importance for the interpretation of future experiments at x-ray free electron lasers operating in the few tens of keV regime, where such nondipole and recoil effects will be essential.

Measurement of relative lung perfusion with electrical impedance and positron emission tomography: an experimental comparative study in pigs.

BACKGROUND: Electrical impedance tomography (EIT) with indicator dilution may be clinically useful to measure relative lung perfusion, but there is limited information on the performance of this technique. METHODS: Thirteen pigs (50-66 kg) were anaesthetised and mechanically ventilated. Sequential changes in ventilation were made: (i) right-lung ventilation with left-lung collapse, (ii) two-lung ventilation with optimised PEEP, (iii) two-lung ventilation with zero PEEP after saline lung lavage, (iv) two-lung ventilation with maximum PEEP (20/25 cm H2O to achieve peak airway pressure 45 cm H2O), and (v) two-lung ventilation under unilateral pulmonary artery occlusion. Relative lung perfusion was assessed with EIT and central venous injection of saline 3%, 5%, and 10% (10 ml) during breath holds. Relative perfusion was determined by positron emission tomography (PET) using 68Gallium-labelled microspheres. EIT and PET were compared in eight regions of equal ventro-dorsal height (right, left, ventral, mid-ventral, mid-dorsal, and dorsal), and directional changes in regional perfusion were determined. RESULTS: Differences between methods were relatively small (95% of values differed by less than 8.7%, 8.9%, and 9.5% for saline 10%, 5%, and 3%, respectively). Compared with PET, EIT underestimated relative perfusion in dependent, and overestimated it in non-dependent, regions. EIT and PET detected the same direction of change in relative lung perfusion in 68.9-95.9% of measurements. CONCLUSIONS: The agreement between EIT and PET for measuring and tracking changes of relative lung perfusion was satisfactory for clinical purposes. Indicator-based EIT may prove useful for measuring pulmonary perfusion at bedside.

Breakdown of the Spectator Concept in Low-Electron-Energy Resonant Decay Processes.

We suggest that low-energy electrons, released by resonant decay processes, experience substantial scattering on the electron density of excited electrons, which remain a spectator during the decay. As a result, the angular emission distribution is altered significantly. This effect is expected to be a common feature of low-energy secondary electron emission. In this Letter, we exemplify our idea by examining the spectator resonant interatomic Coulombic decay of Ne dimers. Our theoretical predictions are confirmed by a corresponding coincidence experiment.

Discrimination of Corynebacterium glutamicum, Brevibacterium flavum and Brevibacterium lactofermentum by restriction pattern analysis of DNA adjacent to the hom gene.

Different strains of Corynebacterium glutamicum, Brevibacterium flavum, and Brevibacterium lactofermentum were analysed for restriction fragment length polymorphism using the homoserine dehydrogenase gene (hom) as a probe. The hybridization patterns obtained PvuII- or Asp700-restriction of chromosomal DNA were specific and distinguishable for each of the three species and identical for the different strains of each species. Thus, the method employed allows rapid distinction of Corynebacterium glutamicum, Brevibacterium flavum, and Brevibacterium lactofermentum. The former species could also be discriminated from the latter two by its resistance to 0.5 g/l of the methionine analog ethionine.

Viability of intramedullary canal bone reamings for continued calcification.

The viability of intramedullary canal bone reamings as a potential bone graft material was examined. Intramedullary bone reamings were obtained from the tibia or femur of three patients during intramedullary nailing procedures. Histologic examination showed bone marrow elements with complete disruption of the marrow compartmental organization. Bone trabeculas were present in a randomly scattered fashion with no structural organization. To assess the viability after reaming of the material for continued calcification, implants of the reaming material were placed in a pocket made in the gluteus maximus muscle of 12 rats. After 7 days, the implanted bone spicules showed evidence of tetracycline label uptake, indicating the material obtained after reaming the intramedullary canal was still viable and capable of continued calcification. That the intramedullary canal bone reamings may be a source of bone graft material is interesting. The reamings appear to continue an osteoproductive capacity when used as a graft.

DNA alkylation by mustard gas in yeast strains of different repair capacity.

Reaction of the toxic and mutagenic alkylating agent mustard gas with DNA of the yeast Saccharomyces cerevisiae was analyzed qualitatively and quantitatively. Within the dose range tested (2 X 10(-5)-2 X 10(-3) M) DNA in vivo is alkylated dose-proportionally. DNA alkylation and relative distribution of purine derivatives are not influenced by the cell's sensitivity towards the mutagen. At LD37 (4.4 X 10(-4) M) the wild type contains 44 300 purine derivatives: 9200 3-alkyladenines (20%), 29600 7-alkylguanines (67%) and 5500 diguaninyl derivates (13%) per genome. In sensitive strains the number of derivates per genome at LD37 is reduced according to the dose reduction factor. Alkylation at the position O6 of guanine by mustard gas cannot be shown, the method's limit of detection being 0.3% amongst purine derivates.

Biological and chemical effects of mustard gas in yeast.

Mustard gas induces inactivation and mutation in yeast. Both effects are dose-proportional, indicating single-hit events. Induction of both effects is influenced by the cell's capacity for DNA dark-repair, whereby the probability of reversion is highest in repair-proficient cells. Binding of mustard gas to cells and probably to DNA is independent of DNA-repair systems. The number of inter-strand cross-links, as determined by assaying for renaturability of alkalidenatured DNA, increases in a dose-proportional manner. At 37% survival an excision-deficient strain contains 55 inter-strand cross-links. Chromatographic analysis yields several alkylation products of DNA. Their relative frequencies resemble the values reported for E. coli and bacteriophage T7.

The fermentative production of L-lysine as an animal feed additive.

A new and innovative process for the biotechnological production of L-lysine is presented, exemplified here by the fermentative production of the feed additive Biolys60. The novel feature of this product is that the entire manufacturing concept, i.e. the production strain, the raw materials, all process stages and the product specifications have been systematically tailored for optimal environmental compatibility and for minimum resource depletion and waste. The process completely dispenses with the need to discharge residual and waste material and reduces the handling of hazardous materials to a minimum. Since only a few process stages are involved, the method is economical to use and investment outlay is reduced. The process, which also leads to a higher grade product, is thus highly attractive in both ecological and economical terms. By boosting the nutrient value of the plant-based feedstuffs, the product itself makes an cost-effective contribution towards a more sustainable form of animal feeding and by reducing nitrogen emission levels promotes a more environmentally compatible form of animal husbandry.

Ulnar nerve laceration in a closed both bone forearm fracture.

Ulnar nerve injury is rarely associated with closed forearm fractures. This report describes a case of ulnar nerve laceration secondary to a closed fracture of the radius and ulna. Although a case report of an ulnar nerve laceration in an open fracture has been described, a review of the literature failed to reveal any cases in closed injuries. The standard surgical approach was modified to allow treatment of the fractures and microscopic repair of the nerve.

Motivation as a factor of perceived exertion in purposeful versus nonpurposeful activity.

Perceived exertion during the performance of purposeful and nonpurposeful activity was studied in 26 women. The subjects acted as their own controls in the performance of both kinds of exercise. The two exercises were jumping rope, defined as a purposeful activity, and jumping in place without a rope, defined as a nonpurposeful activity. In each activity the subjects exercised to reach the subjective point of "very hard work" on the Borg Scale of Perceived Exertion. Duration and cessation of exercise were entirely controlled by the performers. Heart rate responses during and immediately after cessation of exercise, measured by electrocardiographic telemetry, and duration of exercise in seconds were compared for the two types of exercise. Results showed that heart rate increase at a given rate of perceived exertion was significantly higher (.001) for jumping rope. This raises the possibility that workload was inadvertently perceived by the performers to be greater in nonpurposeful activity and provides support for the hypothesis that purposeful activity serves as an intrinsic motivator to the performer.

Intracavernous application of SIN-I in rabbit and man: functional and toxicological results.

The mode of action of the active metabolite SIN-I of the vasodilator prodrug molsidomine was studied in vitro and in vivo in corpus cavernosum of rabbit and man. SIN-I produces a dose-dependent relaxation of isolated human cavernous smooth muscle strips. In the rabbit, the intracavernous application of SIN-I increased the intracavernous pressure to a full erection (approximately 100 cm H2O). This response was highly reproductible. SIN-I was also injected intracavernously 6 times in five rabbits over 2 weeks; no inflammatory or fibrotic reactions were found on histology. SIN-I may be a reliable drug for the treatment of impotence without side-effects.