Yields Of Fragments Research Articles

Yields of projectile fragments in sulphur-emulsion interactions at 3.7 A GeV

This work presents the basic characteristics of singly, doubly and heavily charged projectile fragments (PFs) emitted in inelastic interactions of 32S ions with photo-emulsion nuclei at Dubna energy (3.7 A GeV). Our experimental data are compared with the corresponding data for other projectiles at the same incident energy. The study of mean multiplicities of different charged PFs against the projectile mass shows a power-law relationship. The multiplicity distributions of singly and doubly charged PFs have been fitted well with a Gaussian distribution function. The yields of PFs broken up from the interactions of 32S projectile nuclei with different target nuclei are studied. The beam energy dependence in terms of the various order moments is studied as well.

Differential Fragmentation of Mobility-Selected Glycans via Ultraviolet Photodissociation and Ion Mobility-Mass Spectrometry.

The alternative dissociation pathways initiated by ultraviolet photodissociation (UVPD) compared with collision-induced dissociation (CID) may provide useful diagnostic fragments for biomolecule identification, including glycans. However, underivatized glycans do not commonly demonstrate strong UV absorbance, resulting in low fragmentation yields for UVPD spectra. In contrast to UVPD experiments that leverage covalent modification of glycans, we detail the capacity of metal adduction to yield comparatively rich UVPD fragmentation patterns and enhance separation factors for an isomeric glycan set in a drift tube ion mobility system. Ion mobility and UVPD-MS spectra for two N-acetyl glycan isomers were examined, each adducted with sodium or cobalt cations, with the latter providing fragment yield gains of an order of magnitude versus sodium adducts. Furthermore, our glycan analysis incorporated front-end ion mobility separation such that the structural glycan isomers could still be identified even as a mixture and not simply composite spectra of isomeric standards. Cobalt adduction proved influential in the glycan separation by yielding an isomer resolution of 0.78 when analyzed simultaneously versus no discernable separation obtained with the sodium adducts. It is the combined enhancement of both isomeric drift time separation and isomer distinction with improved UVPD fragment ion yields that further bolster multivalent metal adduction for advancing glycan IM-MS experiments. Graphical Abstract ᅟ.

Fission-fragment mass yields of highly excited nuclei with 119 ≤ A ≤ 218 produced in various reactions

The characteristics of fission fragments of various highly-excited nuclei with 119≤A≤218, which are formed by γ- and α-captures, and by fusion–fission reactions, are discussed in details. The yields of fission fragments of these nuclei are related to the number of states of the two-fragment systems at the two-body saddle points. The various experimental distributions of fission fragments are well described in the model.

Mapping Transposon Insertions in Bacterial Genomes by Arbitrarily Primed PCR.

Transposons can be used to easily generate and label the location of mutations throughout bacterial and other genomes. Transposon insertion mutants may be screened for a phenotype as individual isolates, or by selection applied to a pool of thousands of mutants. Identifying the location of a transposon insertion is critical for connecting phenotype to the genetic lesion. In this unit, we present an easy and detailed approach for mapping transposon insertion sites using arbitrarily-primed PCR (AP-PCR). Two rounds of PCR are used to (1) amplify DNA spanning the transposon insertion junction, and (2) increase the specific yield of transposon insertion junction fragments for sequence analysis. The resulting sequence is mapped to a bacterial genome to identify the site of transposon insertion. In this protocol, AP-PCR as it is routinely used to map sites of transposon insertion within Staphylococcus aureus, is used to illustrate the principle. Guidelines are provided for adapting this protocol for mapping insertions in other bacterial genomes. Mapping transposon insertions using this method is typically achieved in 2 to 3 days if starting from a culture of the transposon insertion mutant. © 2017 by John Wiley & Sons, Inc.

Correlated electron-nuclear dissociation dynamics: classical versus quantum motion

We investigate the coupled electron-nuclear dynamics in a model system which undergoes dissociation. In choosing different initial conditions, the cases of adiabatic and non-adiabatic dissociation are realized. We treat the coupled electronic and nuclear motion in the complete configuration space so that classically, no surface hopping procedures have to be incorporated in the case that more than a single adiabatic electronic state is populated during the fragmentation. Due to the anharmonic interaction potential, it is expected that classical mechanics substantially deviate from quantum mechanics. However, we provide examples where the densities and fragmentation yields obtained from the two treatments are in astonishingly strong agreement in the case that one starts in the electronic ground state initially. As expected, larger deviations are found if one starts in electronically excited states where trajectories are sampled from the more spatially extended electronic wave function. In that case, higher initial energies are accessed, and the motion proceeds in regions with increasing degree of anharmonicity.

Cooling of isolated anthracene cations probed with photons of different wavelengths in the Mini-Ring.

We report on a direct measurement of the Internal Energy Distribution (IED) shift rate of an initially hot polycyclic aromatic hydrocarbon (PAH) molecular ensemble, anthracene cations (C14H10+). The ions were produced in an electron cyclotron resonance (ECR) ion source and stored in an electrostatic ion storage ring, the Mini-Ring. Laser pulses of two wavelengths were sent successively to merge the stored ion bunch at different storage times to enhance the neutral fragment yield due to fast laser induced dissociation. Using this technique, we have been able to determine directly the energy shift rate of the IED, without involving any theoretical simulation or any assumption on dissociation rates, cooling rates, or the initial IED. Theoretical energy shift rates have been estimated from the evolution of simulated IEDs by taking into account the effects of the unimolecular dissociation and two radiative decay mechanisms: the Poincaré fluorescence and the infrared vibrational emission. The comparison between the experimental results and the model provides new evidence of the important role of the Poincaré fluorescence in the overall cooling process of anthracene cations. Although in the short time range the commonly accepted intuition says that the cooling would result mostly from the dissociation of the hottest ions (depletion cooling), we demonstrate that the Poincaré fluorescence is the dominant contribution (about 85%) to the net cooling effect.

Interaction of three fission fragments and yields of various ternary fragments

The interaction potential energy of the three deformed fragments formed in fission of $^{252}\mathrm{Cf}$ is studied for various combinations of three-fragment fission. The lowest height of the potential energy ridge between three touching and separated deformed fragments is sought. The excitation energies of various three-deformed-fragment configurations, at the lowest barrier heights related to the yield of the corresponding configuration, are considered in detail. The most probable three-fragment fission configurations are discussed. The yields of various ternary fragments in fission of $^{250}\mathrm{Cf}$ agree well with available experimental data.

Iron L-Edge Absorption Spectroscopy of Iron Pentacarbonyl and Ferrocene in the Gas Phase.

Fe L-edge X-ray absorption spectra of gas-phase iron pentacarbonyl and ferrocene measured in total-ion yield mode are reported. Comparison to previously published spectra of free iron atoms and gaseous iron chloride demonstrates how the interplay of local atomic multiplet effects and orbital interactions in the metal-ligand bonds varies for the different systems. We find changes in the degree of metal-ligand covalency to be reflected in the measured 2p absorption onset. Orbital- or state-specific fragmentation is furthermore investigated in iron pentacarbonyl and ferrocene by analyzing the partial-ion-yield spectra at the Fe L-edge. Strong dependence of the yields of different fragments is observed in ferrocene in contrast to iron pentacarbonyl. This difference is attributed to the different degrees to which the 2p core hole is screened in the two systems and to which charge is rearranged in the Auger final states. We provide experimental benchmark spectra for new ab initio approaches for calculating metal L-edge absorption spectra of metal complexes.

Local and global even-odd effects in prompt emission in fission

The investigation of the proton even-odd effects in prompt emission in fission for even-Z actinides revealed basic features of the global even-odd effect in prompt emission similar with those in fission fragment yields and some particular aspects, such as: (1) the even-odd effects in prompt emission are the result of two contributions: a dominant intrinsic even-odd effect due to the even-odd nuclear character of fragments reflected in their properties and a weak even-odd effect caused by the fragment distributions (over which the multi-parametric matrices are averaged); (2) oscillations with a periodicity of about 5 mass units are present in different prompt emission quantities corresponding to even-Z and odd-Z fragmentations independent on the size of the even-odd effect in the charge yield Y(Z). These oscillations are due to the periodicity of nuclear properties of fragments; (3) a local even-odd effect in prompt emission quantities has been recently investigated. Similarities between prompt emission quantities and fragment yields were found in the case of the local even-odd effect, too. The local even-odd effect in both fragment charge yields and prompt emission quantities exhibit a pronounced increase at asymmetry values corresponding to fragmentations in which the heavy fragment (Z = 50 and/or N = 82) or the light one (Z = 28) is magic.

Experimental programme on absolute fission fragment yields with the lohengrin spectrometer: New optical and statistical methodologies

The study of fission yields has a major impact on the characterization and understanding of the fission process and is mandatory for reactor applications. The mass and isotopic yields of the fission fragments have a direct influence on the amount of neutron poisons that limit the fuel burnup and on the evaluation of the residual power of the reactor after shutdown. The fission yields of the plutonium nuclides are also mandatory for the studies on the fuel multi-recycling. In order to significantly improve the precision of nuclear data, more and more fundamental fission models are used in the evaluation processing. Therefore, tests of fission models become a central issue to achieve a coherent libraries of nuclear data. In this framework, an important investigation in the experimental limits of facilities is required to provide complete sets of data with their coherent variance-covariance matrices. In the past with the LOHENGRIN spectrometer of the ILL, priority has been given for the studies in the light fission fragment mass range. The LPSC in collaboration with ILL and CEA has developed a measurement program on symmetric and heavy mass fission fragment distributions. The combination of measurements with ionisation chamber and Ge detectors is necessary to describe precisely the heavy fission fragment region in mass and charge. Recently, new measurements of fission yields and kinetic energy distributions, with different fissioning systems, were performed with this facility. The focus has been done on the selfnormalization of the data to provide new absolute measurements, independently of any libraries, and the experimental covariance matrix. To reach precise measurements, a new experimental procedure was developed along with a new analysis method based on metadata. Because of the complex correction scheme from count rates to yields, a classical propagation uncertainty is not possible. The new analysis path gives the mean value of mass yields, its probability density function and the associated experimental variance-covariance matrices. All this information is a first step to bring nuclear data into statistical tests of the underlying hypothesis of fission models.

Fragmentation of light nuclei by intermediate energy photons

New data on the fragmentation of carbon nuclei by photons with energies from 800 to 1500 MeV, obtained in the collaboration GRAAL, are presented. These data include the yields of heavier fragments than nucleons. Comparison of new results with literature data, obtained with real and virtual photons in reactions with electrons and relativistic ions (Coulomb dissociation) is done using a general approach in frame of the Weizsacker–Williams model. Possible reasons for the observed differences between them are discussed.

Emission of d, t,3He andα-particles from12C nuclei excited by intermediate energy photons

New GRAAL data on the fragmentation of carbon nuclei by photons at 800 - 1500 MeV are discussed. In addition to previously published results for the proton and neutron emission probabilities at different multiplicities, preliminary results on the yields of heavier fragments as d, t, 3 He and α -particles are presented. The obtained results are compared with theoretical predictions and other fragmentation data measured in different reactions induced by photons, electrons and relativistic ions.

A broader view on ion heating in traveling-wave devices using fragmentation of CsI clusters and extent of H˙ migration as molecular thermometers.

Electron transfer dissociation (ETD) is becoming increasingly important in mass spectrometry-based analysis of peptides and proteins. Supplemental collisional activation of undissociated electron transfer products can significantly increase fragmentation yield and sequence coverage, but hydrogen rearrangements - specifically, transfer of a hydrogen radical from a c to a z fragment - lead to distorted isotope distributions and increased potential for signal overlap. Concomitant collisional activation during the ion/ion reaction significantly reduces these rearrangements, but, in ion traps, also leads to lower reaction rates and reduced overlap of anion and cation clouds. In traveling-wave ion mobility devices, it has been reported - although not under ETD conditions - that significant ion activation can occur depending on the T-wave height and velocity. Here, we investigate this phenomenon in more detail using a commercial instrument (Waters Synapt G2) and report that a similar effect can be induced within the traveling-wave Trap cell where the ETD reaction occurs, using fairly typical T-wave settings. This ion 'heating' is demonstrated by analyzing the observed isotope distributions (sensitive to the aforementioned hydrogen rearrangements) of ETD fragments of ubiquitin and substance P. A more detailed investigation of ion activation using cesium iodide clusters (without ETD reagent anions present) shows that the observed behavior is consistent with the known dynamics of ions within traveling-wave devices. The insights gained in this work are potentially relevant both for 'native ETD' studies (in which tuning needs to be optimized to avoid unintentional ion activation) as well as the design of future T-wave ETD devices (where this 'heating' effect might be exploited to promote fragment release).

Odd-even effect dependence on the excitation energy in low energy fission

An inversion of the odd-even effect was observed experimentally in cold fission: the odd-odd fragmentation yields are favored over the even-even ones for excitations energies of the fragments smaller than 4 MeV. This effect is linked to the important problem of quasiparticle excitations during the dynamical evolution of the nuclear system from its ground-state configuration up to scission. An explanation based on the Landau-Zener promotion mechanism generalized for superfluid systems is offered for the inversion of the odd-even effect. In principle, the even-even fission products cannot be produced at very low excitation energies due dynamical quasiparticle excitations produced in the avoided- level-crossing regions. These excitations are produced with a large probability when the nuclear system deforms slowly.

Production of neutron-rich exotic nuclei in projectile fragmentation at Fermi energies

Isotopic fragment yields of projectile fragmentation in peripheral collisions of \(^{86}\hbox {Kr}\) on \(^{124,112}\hbox {Sn}\) and the mean neutron-to-proton ratios of the fragments are calculated, theoretically, within the ensemble approach of statistical multifragmentation model. Obtained data are compared to the experimental cross-section measurements for the projectile-like fragmentation in the reaction of 25 MeV/nucleon \(^{86}\hbox {Kr}\)+\(^{124,112}\hbox {Sn}\) at Texas A&M University. We show the enhancement in the production of neutron-rich isotopes close to the projectile as observed in the experiments. We also demonstrate the universality of the limitation of the excitation energy induced in the projectile residues.

Proton induced fission of 232Th at intermediate energies

The mass-energy distributions and cross sections of proton-induced fission of 232Th have been measured at the proton energies of 7, 10, 13, 20, 40, and 55 MeV. Experiments were carried out at the proton beam of the K-130 cyclotron of the JYFL Accelerator Laboratory of the University of Jyvaskyla and U-150m cyclotron of the Institute of Nuclear Physics, Ministry of Energy of the Republic of Kazakhstan. The yields of fission fragments in the mass range A = 60–170 a.m.u. have been measured up to the level of 10−4%. The three humped shape of the mass distribution up has been observed at higher proton energies. The contribution of the symmetric component grows up with increasing proton incident energy; although even at 55 MeV of proton energy the shoulders in the mass energy distribution clearly indicate the asymmetric fission peaks. Evolution of shell structure was observed in the fission fragment mass distributions even at high excitation energy.

Mass yields and kinetic energy of fragments from fission of highly-excited nuclei with A≲220

It is shown that the potential energy surface of the two separated fragments has the saddle point, which takes place at small distance between the surfaces of well-deformed fragments. The height of this two-body saddle point is larger than the height of one-body fission barrier for nuclei with A≲220. The mass yields of the fission fragments, which are appearing at the fission of nuclei with A≲220, are related to the number of states of the two-fragment systems at the two-body saddle points. The characteristics of kinetic energy of fragments are described by using the trajectory motion equations with the dissipation terms. The Gaussian distribution of the final kinetic energy around the classical value of this energy induced by the stochastic fluctuations is taken into account at an evaluation of the total kinetic energy distributions of the fission fragments.

Toward a suitable structural analysis of gene delivery carrier based on polycationic carbohydrates by electron transfer dissociation tandem mass spectrometry

Polycationic carbohydrates represent an attractive class of biomolecules for several applications and particularly as non viral gene delivery vectors. In this case, the establishment of structure-biological activity relationship requires sensitive and accurate characterization tools to both control and achieve fine structural deciphering. Electrospray-tandem mass spectrometry (ESI-MS/MS) appears as a suitable approach to address these questions. In the study herein, we have investigated the usefulness of electron transfer dissociation (ETD) to get structural data about five polycationic carbohydrates demonstrated as promising gene delivery agents. A particular attention was paid to determine the influence of charge states as well as both fluoranthene reaction time and supplementary activation (SA) on production of charge reduced species, fragmentation yield, varying from 2 to 62%, as well as to obtain the most higher both diversity and intensity of fragments, according to charge states and targeted compounds. ETD fragmentation appeared to be mainly directed toward pending group rather than carbohydrate cyclic scaffold leading to a partial sequencing for building blocks when amino groups are close to carbohydrate core, but allowing to complete structural deciphering of some of them, such as those including dithioureidocysteaminyl group which was not possible with CID only. Such findings clearly highlight the potential to help the rational choice of the suitable analytical conditions, according to the nature of the gene delivery molecules exhibiting polycationic features. Moreover, our ETD-MS/MS approach open the way to a fine sequencing/identification of grafted groups carried on various sets of oligo-/polysaccharides in various fields such as glycobiology or nanomaterials, even with unknown or questionable extraction, synthesis or modification steps.

Performance of Streck cfDNA Blood Collection Tubes for Liquid Biopsy Testing.

ObjectivesMaking liquid biopsy testing widely available requires a concept to ship whole blood at ambient temperatures while retaining the integrity of the cell-free DNA (cfDNA) population and stability of blood cells to prevent dilution of circulating tumor DNA (ctDNA) with wild-type genomic DNA. The cell- and DNA-stabilizing properties of Streck Cell-Free DNA BCT blood collection tubes (cfDNA BCTs) were evaluated to determine if they can be utilized in combination with highly sensitive mutation detection technologies.MethodsVenous blood from healthy donors or patients with advanced colorectal cancer (CRC) was collected in cfDNA BCTs and standard K2EDTA tubes. Tubes were stored at different temperatures for various times before plasma preparation and DNA extraction. The isolated cfDNA was analyzed for overall DNA yield of short and long DNA fragments using qPCR as well as for mutational changes using BEAMing and Plasma Safe-Sequencing (Safe-SeqS).ResultsCollection of whole blood from healthy individuals in cfDNA BCTs and storage for up to 5 days at room temperature did not affect the DNA yield and mutation background levels (n = 60). Low-frequency mutant DNA spiked into normal blood samples as well as mutant circulating tumor DNA in blood samples from CRC patients collected in cfDNA BCTs were reliably detected after 3 days of storage at room temperature. However, blood samples stored at ≤ 10°C and at 40°C for an extended period of time showed elevated normal genomic DNA levels and an abnormally large cellular plasma interface as well as lower plasma volumes.ConclusionWhole blood shipped in cfDNA BCTs over several days can be used for downstream liquid biopsy testing using BEAMing and Safe-SeqS. Since the shipping temperature is a critical factor, special care has to be taken to maintain a defined room temperature range to obtain reliable mutation testing results.

Standardization of CalyculinA induced PCC assay and its advantages over Okadaic acid PCC assay in Biodosimetry applications.

In the present study an attempt was made to estimate coefficients of dose response curves for PCC aberrations induced by CalyculinA and Okadaic acid, using 60Co gamma radiation and 8 MeV pulsed electron beam for biodosimetry application. The modified method outlined by Puig et al. 2013 was used to conduct Calyculin A and Okadaic acid induced PCC assay in human blood lymphocytes.Chemical treatment was given for the last 1 h of a 48 h culture. The study was carried out in the dose range 2.5 to 20 Gy using 60Co gamma rays and 8 MeV pulsed electron beam. Results show a linear dose dependent increase with a slope of 0.047 ± 0.001 from Calycalin A PCC and 0.048 ± 0.002 form Okadaic acid PCC. The slope of the fragments curve was 0.327 ± 0.006 from Calyculin A and 0.328 ± 0.006 from Okadaic acid PCC. Further, dose calibration studies were carried out for 8 MeV electron using Calyculin A PCC assay and the obtained slope from ring yield was 0.054 ± 0.002 and 0.427 ± 0.009 from fragment yield.