Study of refractive structure in the inelastic 16O+16O scattering at the incident energies of 250 to 1120 MeV

The data of inelastic 16O+16O scattering to the lowest 2+ and 3- excited states of 16O have been measured at Elab = 250, 350, 480, 704 and 1120 MeV and analyzed consistently in the distorted wave Born approximation (DWBA), using the semi- microscopic optical potentials and inelastic form factors given by the folding model, to reveal possible refractive structure of the nuclear rainbow that was identified earlier in the elastic 16O+16O scattering channel at the same energies. Given the known transition strengths of the 2+ and 3- states of 16O well determined from the (e,e') data, the DWBA description of the inelastic data over the whole angular range was possible only if the absorption in the exit channels is significantly increased (especially, for the 16O+16O(2+) exit channel). Although the refractive pattern of the inelastic 16O+16O scattering was found to be less pronounced compared to that observed in the elastic scattering channel, a clear remnant of the main rainbow maximum could still be seen in the inelastic cross section at Elab = 350 - 704 MeV.Comment: 26 pages, 10 figures, Accepted for publication in Nucl. Phys.

Nuclear rainbow scattering and nucleus-nucleus potential

Elastic scattering of alpha-particle and some tightly-bound light nuclei has shown the pattern of rainbow scattering at medium energies, which is due to the refraction of the incident wave by a strongly attractive nucleus-nucleus potential. This review gives an introduction to the physics of the nuclear rainbow based essentially on the optical model description of the elastic scattering. Since the realistic nucleus-nucleus optical potential (OP) is the key to explore this interesting process, an overview of the main methods used to determine the nucleus-nucleus OP is presented. The refractive rainbow-like structures observed in other quasi-elastic scattering reactions have also been discussed. Some evidences for the refractive effect in the elastic scattering of unstable nuclei are presented and perspectives for the future studies are discussed

Tides and Overtides in Long Island Sound

Using observations obtained by acoustic Doppler profilers and coastal water level recorders, we describe the vertical and horizontal structure of the currents and sea level due to the principal tidal constituents in Long Island Sound, a shallow estuary in southern New England. As expected, the observations reveal that M2 is the dominant constituent in both sea surface and velocity at all depths and sites. We also find evidence that the vertical structure of the M2 tidal current ellipse parameters vary with the seasonal evolution of vertical stratification at some sites. By comparing our estimates of the vertical structure of the M2 amplitudes to model predictions, we demonstrate that both uniform and vertically variable, time invariant eddy viscosities are not consistent with our measurements in the Sound. The current records from the western Sound contain significant overtides at the M4 and M6 frequencies with amplitudes and phases that are independent of depth. Though the M4 amplitude decreases to the west in proportion to M2, the M6 amplifies. Since the dynamics that generate overtides also produce tidal residuals, this provides a sensitive diagnostic of the performances of numerical circulation models. We demonstrate that the observed along-Sound structure of the amplitude of the M4 and M6 overtides is only qualitatively consistent with the predictions of a nonlinear, laterally averaged layer model forced by a mean flow and sea level at the boundaries. Since neither the vertical structure of the principal tidal constituent nor the pattern of horizontal variation of the largest overtides can be explained using well established models, we conclude that they are fundamentally inadequate and should no longer be used for more than a basic qualitative understanding, and even then should be used with caution. We provide comprehensive tables of the tidal current parameters to facilitate the critical evaluation of future models of the circulation in the Sound

A perpetual switching system in pulmonary capillaries

Of the 300 billion capillaries in the human lung, a small fraction meet normal oxygen requirements at rest, with the remainder forming a large reserve. The maximum oxygen demands of the acute stress response require that the reserve capillaries are rapidly recruited. To remain primed for emergencies, the normal cardiac output must be parceled throughout the capillary bed to maintain low opening pressures. The flow-distributing system requires complex switching. Because the pulmonary microcirculation contains contractile machinery, one hypothesis posits an active switching system. The opposing hypothesis is based on passive switching that requires no regulation. Both hypotheses were tested ex vivo in canine lung lobes. The lobes were perfused first with autologous blood, and capillary switching patterns were recorded by videomicroscopy. Next, the vasculature of the lobes was saline flushed, fixed by glutaraldehyde perfusion, flushed again, and then reperfused with the original, unfixed blood. Flow patterns through the same capillaries were recorded again. The 16-min-long videos were divided into 4-s increments. Each capillary segment was recorded as being perfused if at least one red blood cell crossed the entire segment. Otherwise it was recorded as unperfused. These binary measurements were made manually for each segment during every 4 s throughout the 16-min recordings of the fresh and fixed capillaries (>60,000 measurements). Unexpectedly, the switching patterns did not change after fixation. We conclude that the pulmonary capillaries can remain primed for emergencies without requiring regulation: no detectors, no feedback loops, and no effectors-a rare system in biology. NEW & NOTEWORTHY The fluctuating flow patterns of red blood cells within the pulmonary capillary networks have been assumed to be actively controlled within the pulmonary microcirculation. Here we show that the capillary flow switching patterns in the same network are the same whether the lungs are fresh or fixed. This unexpected observation can be successfully explained by a new model of pulmonary capillary flow based on chaos theory and fractal mathematics

Structure of 10Be from the 12C 12C,14O 10Be reaction

The 12C 12C,14O two proton pick up reaction has been measured at 211.4 MeV incident energy to study the structure of states of 10Be up to excitation energies of 12 MeV. The measured partial angular distributions show pronounced oscillatory shapes, which were described by coupled reaction channels calculations. Spin parity assignments could be derived from these characteristic shapes and two definite assignments have been made. The state at 11.8 MeV has been identified as the 4 member of the ground state band, and the state at 10.55 MeV is assigned J pi 3 . At 5.96 MeV only the 1 1 member of the known 2 2 1 1 doublet is populated. The angular distribution of the peak at 9.50 MeV, which consists of several unresolved states, has been unfolded using contributions from known states at 9.56 MeV, 2 , and 9.27 MeV, 4 . The inclusion of a state at 9.4 MeV reported by Daito it et al. from the 10B t,3He 10Be reaction and tentatively assigned 3 improved the fit considerably. A K 2 band is formed with the 2 2 state as the band head and the 3 state as the second member. The structures of the K pi 0 1, 2 2, and 1 1 bands are discusse

Heterobimetallic Au(I)/Y(III) single chain nanoparticles as recyclable homogenous catalysts

Heterobimetallic single chain nanoparticles were synthesized and applied as recyclable homogenous catalysts. A terpolymer containing two orthogonal ligand moieties, phosphines and carboxylates, was obtained via nitroxide-mediated polymerization. Single chain nanoparticle (SCNP) formation is induced by selective metal complexation of Y(III) by the carboxylate functions, while Au(I) is selectively coordinated to phosphine moieties. In contrast to previous work, the two functionalities, SCNP folding and formation of a catalytic center, were distributed over two metals, which critically increases the flexibility of the system. The formation of Au(I)/Y(III)-SCNPs is evidenced by size exclusion chromatography, dynamic light scattering, nuclear magnetic resonance (1H, 31P{1H}) and infrared spectroscopy. Importantly, the activity of the Au(I)/Y(III)-SCNPs as homogenous, yet recyclable catalyst, bridging the gap between homogenous and heterogeneous catalysis, was demonstrated using the hydroamination of aminoalkynes as an example

Влияние пластификации на тепловое расширение полимеров

В статье рассмотрено влияние пластификации и модификации некоторых полимеров на температуру стеклования и параметры теплового расширения. В термопластичных полимерах, с достаточно гибкими макромолекулярными цепями, введение пластификатора или модификатора не влияет на величину свободного объема при Т=ТС и поведение таких систем подчиняется эмпирическому правилу Симха и Бойера. Отклонения от него наблюдаются лишь при больших концентрациях пластификатора, ограниченно совмещающегося с полимером

Behavior studies related to pesticides: Urban chemical pesticides and Iowa urban chemical-pesticide dealers

As reflected in sales reports, millions of people are using chemical pesticides to solve a number of problems. Estimated total cost of chemical pesticides to all United States users in 1965 was more than a billion dollars. Farmers used pesticides costing an estimated $590 million-58 percent of the total. Residential (home, lawn, and garden) purchases amounted to about$220 million or about 22 percent of the total. The remaining purchases were made by industrial, institutional, and governmental sources. The use of chemical pesticides is expected to increase in the following year. The use of chemical pesticides has not, however, been accepted by everyone. Concern has been voiced about possible consequences of improper use of these chemicals to the user as well as to wildlife, pets and agricultural commodities. This concern has been expressed in proposals to limit or abolish the use of chemical pesticides. The subject is controversial, but there have been few valid data on which to base rational discussion. Little research work has been done in determining attitudes, knowledge, and use and sales patterns of individuals in relation to chemical pesticides. Similarly, little is known about the people who sell chemicals to the ultimate consumer; i.e., what the dealers’ levels of knowledge and attitudes are; what their perceptions of possible harmful consequences are; what information they provide; and what they perceive their role to be

Rates and regulation of nitrogen cycling in seasonally hypoxic sediments during winter (Boknis Eck, SW Baltic Sea): Sensitivity to environmental variables

This study investigates the biogeochemical processes that control the benthic fluxes of dissolved nitrogen (N) species in Boknis Eck - a 28 m deep site in the Eckernförde Bay (southwestern Baltic Sea). Bottom water oxygen concentrations (O2-BW) fluctuate greatly over the year at Boknis Eck, being well-oxygenated in winter and experiencing severe bottom water hypoxia and even anoxia in late summer. The present communication addresses the winter situation (February 2010). Fluxes of ammonium (NH4+), nitrate (NO3-) and nitrite (NO2-) were simulated using a benthic model that accounted for transport andbiogeochemical reactions and constrained with ex situ flux measurements and sediment geochemical analysis. The sediments were a net sink for NO3- (-0.35 mmol m-2 d-1 of NO3-), of which 75% was ascribed to dissimilatory reduction of nitrate to ammonium (DNRA) by sulfide oxidizing bacteria, and 25% to NO3- reduction to NO2- by denitrifying microorganisms. NH4+ fluxes were high (1.74 mmol m-2d-1 of NH4+), mainly due to the degradation of organic nitrogen, and directed out of the sediment. NO2-fluxes were negligible. The sediments in Boknis Eck are, therefore, a net source of dissolved inorganic nitrogen(DIN = NO3- + NO2- + NH4+) during winter. This is in large part due to bioirrigation, which accounts for 76% of the benthic efflux of NH4+, thus reducing the capacity for nitrification of NH4+. The combined rate of fixed N loss by denitrification and anammox was estimated at 0.08 mmol m-2 d-1 of N2, which is at the lower end of previously reported values. A systematic sensitivity analysis revealed that denitrification and anammox respond strongly and positively to the concentration of NO3- in the bottomwater (NO3-BW).Higher O2-BW decreases DNRA and denitrification but stimulates both anammox and the contribution ofanammox to total N2 production (%Ramx). A complete mechanistic explanation of these findings is provided. Our analysis indicates that nitrification is the geochemical driving force behind the observed correlation between %Ramx and water depth in the seminal study of Dalsgaard et al. (2005). Despite remaining uncertainties, the results provide a general mechanistic framework for interpreting the existing knowledge of N-turnover processes and fluxes in continental margin sediments, as well as predicting the types of environment where these reactions are expected to occur prominently