Study of the polyoxymethylene and its sputtered fragments: Implications for comets

Laboratory mass spectra of sputtered polyoxymethylene (POM) reveals a fragmentation pattern consistent with observed peaks in the PICCA experiment on board the Giotto spacecraft. Both commercially available POM and radiation synthesized POM have been used in the studies. Synthesized POM was identified using infrared absorption spectra after proton irradiation of H2CO ice on silicate grains at 20 K. Laboratory results suggest that similar type sputtering is a possible mechanism for removing species from comet grains

QCD motivated approach to soft interactions at high energies: nucleus-nucleus and hadron-nucleus collisions

In this paper we consider nucleus-nucleus and hadron-nucleus reactions in the kinematic region: g A^{1/3} G_{3\pom} \exp\Lb \Delta Y\Rb \approx 1 G^2_{3\pom} \exp\Lb \Delta Y\Rb \approx 1 , where G_{3\pom} is the triple Pomeron coupling, $g$ is the vertex of Pomeron nucleon interaction, and 1 + \Delta_{\pom} denotes the Pomeron intercept. We find that in this kinematic region the traditional Glauber-Gribov eikonal approach is inadequate. We show that it is necesssary to take into account inelastic Glauber corrections, which can not be expressed in terms of the nucleon-nucleon scattering amplitudes. In the wide range of energies where \alpha'_\pom Y \ll R^2_A,the scattering amplitude for the nucleus-nucleus interaction, does not depend on the details of the nucleon-nucleon interaction at high energy. In the formalism we present, the only (correlated) parameters that are required to describe the data are \Delta_{\pom}, G_{3\pom} and $g$. These parameters were taken from our description of the nucleon-nucleon data at high energies \cite{GLMM}.The predicted nucleus modification factor is compared with RHIC Au-Au data at $W = 200 GeV.$ Estimates for LHC energies are presented and discusssed.Comment: 18pp. 14 fugure

Applying Item Response Theory (IRT) Modeling to an Observational Measure of Childhood Pragmatics: The Pragmatics Observational Measure-2

Assessment of pragmatic language abilities of children is important across a number of childhood developmental disorders including ADHD, language impairment and Autism Spectrum Disorder. The Pragmatics Observational Measure (POM) was developed to investigate children's pragmatic skills during play in a peer-peer interaction. To date, classic test theory methodology has reported good psychometric properties for this measure, but the POM has yet to be evaluated using item response theory. The aim of this study was to evaluate the POM using Rasch analysis. Person and item fit statistics, response scale, dimensionality of the scale and differential item functioning were investigated. Participants included 342 children aged 5-11 years from New Zealand; 108 children with ADHD were playing with 108 typically developing peers and 126 typically developing age, sex and ethnic matched peers played in dyads in the control group. Video footage of this interaction was recorded and later analyzed by an independent rater unknown to the children using the POM. Rasch analysis revealed that the rating scale was ordered and used appropriately. The overall person (0.97) and item (0.99) reliability was excellent. Fit statistics for four individual items were outside acceptable parameters and were removed. The dimensionality of the measure showed two distinct elements (verbal and non-verbal pragmatic language) of a unidimensional construct. These findings have led to a revision of the first edition of POM, now called the POM-2. Further empirical work investigating the responsiveness of the POM-2 and its utility in identifying pragmatic language impairments in other childhood developmental disorders is recommended

Hydrologic controls on seasonal and inter-annual variability of Congo River particulate organic matter source and reservoir age

We present dissolved organic carbon (DOC) concentrations, particulate organic matter (POM) composition (δ13C, δ15N, ∆14C, N/C), and particulate glycerol dialkyl glycerol tetraether (GDGT) distributions from a 34-month time-series near the mouth of the Congo River. An end-member mixing model using δ13C and N/C indicates that exported POM is consistently dominated by C3 rainforest soil sources, with increasing contribution from C3 vegetation and decreasing contribution from phytoplankton at high discharge. Large C4 inputs are never observed despite covering ≈ 13% of the catchment. Low and variable ∆14C values during 2011 [annual mean = (− 148 ± 82) ‰], when discharge from left-bank tributaries located in the southern hemisphere reached record lows, likely reflect a bias toward pre-aged POM derived from the Cuvette Congolaise swamp forest. In contrast, ∆14C values were stable near − 50‰ between January and June 2013, when left-bank discharge was highest. We suggest that headwater POM is replaced and/or diluted by C3 vegetation and pre-aged soils during transit through the Cuvette Congolaise, whereas left-bank tributaries export significantly less pre-aged material. GDGT distributions provide further evidence for seasonal and inter-annual variability in soil provenance. The cyclization of branched tetraethers and the GDGT-0 to crenarchaeol ratio are positively correlated with discharge (r ≥ 0.70; p-value ≤ 4.3 × 10− 5) due to the incorporation of swamp-forest soils when discharge from right-bank tributaries located in the northern hemisphere is high. Both metrics reach record lows during 2013, supporting our interpretation of increased left-bank contribution at this time. We conclude that hydrologic variability is a major control of POM provenance in the Congo River Basin and that tropical wetlands can be a significant POM source despite their small geographic coverage

Going through a quantum phase

Phase measurements on a single-mode radiation field are examined from a system-theoretic viewpoint. Quantum estimation theory is used to establish the primacy of the Susskind-Glogower (SG) phase operator; its phase eigenkets generate the probability operator measure (POM) for maximum likelihood phase estimation. A commuting observables description for the SG-POM on a signal x apparatus state space is derived. It is analogous to the signal-band x image-band formulation for optical heterodyne detection. Because heterodyning realizes the annihilation operator POM, this analogy may help realize the SG-POM. The wave function representation associated with the SG POM is then used to prove the duality between the phase measurement and the number operator measurement, from which a number-phase uncertainty principle is obtained, via Fourier theory, without recourse to linearization. Fourier theory is also employed to establish the principle of number-ket causality, leading to a Paley-Wiener condition that must be satisfied by the phase-measurement probability density function (PDF) for a single-mode field in an arbitrary quantum state. Finally, a two-mode phase measurement is shown to afford phase-conjugate quantum communication at zero error probability with finite average photon number. Application of this construct to interferometric precision measurements is briefly discussed

Direct calculation of the triple-pomeron coupling for diffractive DIS and real photoproduction

We present a unified direct calculation of the triple-pomeron coupling A_{3\Pom}(Q^{2}) for diffractive real photoproduction ($Q^{2}=0$) and deep inelastic scattering at large $Q^{2}$ in the framework of the dipole approach to the generalized BFKL pomeron. The small phenomenological value of A_{3\Pom}(0)\approx 0.16\,GeV$^{2}$, which was a mystery, is related to the small correlation radius $R_{c}\approx 0.3$\,fm for the perturbative gluons. We confirm the early expectations of weak $Q^{2}$ dependence of the dimensionfull coupling A_{3\Pom}(Q^{2}) and predict that it rises by the factor $\sim 1.6$ from real photoproduction to deep inelastic scattering.Comment: 14 pages, 1 figure (request from [email protected]), Juelich preprint KFA-IKP(Th)-1994-3

Design, synthesis, conformational analysis and nucleic acid hybridisation properties of thymidyl pyrrolidine-amide oligonucleotide mimics (POM)

Pyrrolidine-amide oligonucleotide mimics (POM) 1 were designed to be stereochemically and conformationally similar to natural nucleic acids, but with an oppositely charged, cationic backbone. Molecular modelling reveals that the lowest energy conformation of a thymidyl-POM monomer is similar to the conformation adopted by ribonucleosides. An e cient solution phase synthesis of the thymidyl POM oligomers has been developed, using both N-alkylation and acylation coupling strategies. 1H NMR spectroscopy con rmed that the highly water soluble thymidyl-dimer, T2-POM, preferentially adopts both a con guration about the pyrrolidine N-atom and an overall conformation in D2O that are very similar to a typical C3 -endo nucleotide in RNA. In addition the nucleic acid hybridisation properties of a thymidyl-pentamer, T5-POM, with an N-terminal phthalimide group were evaluated using both UV spectroscopy and surface plasmon resonance (SPR). It was found that T5-POM exhibits very high a nity for complementary ssDNA and RNA, similar to that of a T5-PNA oligomer. SPR experiments also showed that T5-POM binds with high sequence delity to ssDNA under near physiological conditions. In addition, it was found possible to attenuate the binding a nity of T5-POM to ssDNA and RNA by varying both the ionic strength and pH. However, the most striking feature exhibited by T5-POM is an unprecedented kinetic binding selectivity for ssRNA over DNA

Polyoxometalate-intercalated layered double hydroxides as efficient and recyclable bi-functional catalysts for cascade reactions

The polyoxometalate (POM) intercalated-layered double hydroxides (LDHs) have been widely used as heterogeneous catalysts. However, the application of POM-LDHs as bi-functional catalysts for cascade reaction has seldom been studied comparing with the noble metal-based catalysts. Herein, a series of POM-LDHs catalysts of Tris-LDH-X4(PW9)2 (X = Mn, Fe, Co, Ni, Cu and Zn) has been prepared; The efficacy of Tris-LDH-Zn4(PW9)2 as efficient bi-functional catalyst has been demonstrated for cascade reactions involving oxidation of benzyl alcohol to benzaldehyde followed by Knoevenagel condensation with ethyl cyanoacetate to produce benzylidene ethyl cyanoacetate. The combination of POM's redox/acidic sites and LDHs's basic sites led to a composite catalyst with excellent activity (99%) and selectivity (≥ 99%) under mild and soluble-base-free conditions. This work offer a new design strategy for the fabrication of efficient bi-functional catalysts for the promotion of one-pot cascade reactions