Search

We have developed a new class of sodium carbonate/silicone composite sorbents that selectively capture carbon dioxide (CO2) and can purify biogas to natural gas pipeline-quality biomethane. These nontoxic composites can be three-dimensionally printed or extruded at low costs, can have high specific CO2 sorption rates (in excess of 5 μmol s-1 g-1 bar-1) and high selectivity due to their chemical mechanism, and can be regenerated with low-energy air stripping. Therefore, these composite sorbents combine the high selectivity of liquid sorbents with the high specific sorption rates and low regeneration energies found in many solid sorbents. We characterized these composite sorbents with X-ray computed tomography, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Furthermore, we measured composite sorption capacities of up to 0.62 mol CO2 kg-1 and recorded breakthrough curves in a flow-through, fixed-bed reactor using both simulated biogas and locally sourced industrial biogas. Additional tests of the composite sorbent were carried out with pure CO2 in a sealed pressure drop apparatus. This experimental data was used to validate a numerical model of the setup and to simulate an industrial-scale biogas upgrading process. Finally, we performed a preliminary technoeconomic analysis for this upgrading process and found that this composite sorbent can upgrade biogas at a lower cost (∼$0.97 per GJ) than other currently implemented techniques.

Chronic inflammation that affects primarily metabolic organs, such as white adipose tissue (WAT), is considered as a major cause of human obesity-associated co-morbidities. However, the molecular mechanisms initiating this inflammation in WAT are poorly understood. By combining transcriptomics, ChIP-seq and modeling approaches, we studied the global early and late responses to a high-fat diet (HFD) in visceral (vWAT) and subcutaneous (scWAT) AT, the first being more prone to obesity-induced inflammation. HFD rapidly triggers proliferation of adipocyte precursors within vWAT. However, concomitant antiadipogenic signals limit vWAT hyperplastic expansion by interfering with the differentiation of proliferating adipocyte precursors. Conversely, in scWAT, residing beige adipocytes lose their oxidizing properties and allow storage of excessive fatty acids. This phase is followed by tissue hyperplastic growth and increased angiogenic signals, which further enable scWAT expansion without generating inflammation. Our data indicate that scWAT and vWAT differential ability to modulate adipocyte number and differentiation in response to obesogenic stimuli has a crucial impact on the different susceptibility to obesity-related inflammation of these adipose tissue depots. Electronic supplementary material The online version of this article (10.1007/s00018-020-03485-z) contains supplementary material, which is available to authorized users.

We have developed polymer composite inks that may be three-dimensionally (3D) printed to produce new reactor designs for CO2 capture. These inks are composed of solid sodium carbonate particles dispersed within an uncured silicone and are printed using direct ink writing (DIW). After printing, the silicone is cured, and the structures are hydrated to form aqueous sodium carbonate domains dispersed throughout the silicone. These domains enable high CO2 absorption rates by creating domains with high surface area of solvent per unit volume in the printed structures. These results demonstrate an order-of-magnitude improvement in CO2 absorption rates relative to a liquid pool of sodium carbonate. The results from this class of composite inks demonstrate the potential for the use of 3D printing to shape new and advanced CO2 capture reactors.

We encapsulated six solvents with novel physical and chemical properties for CO2 sorption within gas-permeable polymer shells, creating Micro-Encapsulated CO2 Sorbents (MECS), to improve the CO2 absorption kinetics and handling of the solvents for postcombustion CO2 capture from flue gas. The solvents were sodium carbonate (Na2CO3) solution, uncatalyzed and with two different promoters, two ionic liquid (IL) solvents, and one CO2-binding organic liquid (CO2BOL). We subjected each of the six MECS to multiple CO2 absorption and regeneration cycles and measured the working CO2 absorption capacity as a function of time to identify promising candidate MECS for large-scale carbon capture. We discovered that the uncatalyzed Na2CO3 and Na2CO3-sarcosine MECS had lower CO2 absorption rates relative to Na2CO3-cyclen MECS over 30 min of absorption, while the CO2BOL Koechanol appeared to permeate through the capsule shell and is thus unsuitable. We rigorously tested the most promising three MECS (Na2CO3-cyclen, IL NDI...

Micro-Encapsulated CO2 Sorbents (MECS) are a promising technology for post-combustion carbon capture because they enable slow-reacting solvents like carbonate solution to compete with traditional amine solvents. Before scaling up MECS for pilot testing, modeling is needed to design a MECS absorber and quantify its size and energy penalty. To that end, a multi-scale model for MECS- that ranges from a single capsule to a 500 MWe power plant absorber- is developed and presented here. First, the individual capsule model is developed and fitted to experimental CO2 absorption data collected on a 0.1 g sample of capsules filled with sodium carbonate solution. This capsule model is then validated against data collected on a 25 g batch of capsules exposed to flue gas conditions in a fluidized column. This model is then scaled up to represent two absorber designs: a multi-stage, counter-flow fluidized bed and a hollow, cylindrical packed bed with radial gas flow. These two absorber bed models are first optimized for a 1 MWe pilot-scale absorber, and then optimized for a 500 MWe coal plant. This model predicts absorbers of similar dimensions and smaller energy penalties than previously modeled absorbers filled with amine solvent capsules. Furthermore, it is demonstrated here that a few reasonable improvements to capsule design would result in absorber sizes and energy penalties lower than those of a benchmark amine solvent tower. These results demonstrate that micro-encapsulated carbonate solution can compete with faster-acting amine solvents for post-combustion carbon capture.

Candida albicans is a commensal of human mucosae, but also one of the most common fungal pathogens of humans. Systemic infections caused by this fungus, mostly affecting immunocompromised patients, are associated to fatality rates as high as 50% despite the available treatments. In order to improve this situation, it is necessary to fully understand how C. albicans is able to cause disease and how it copes with the host defenses. Our previous studies have revealed the importance of the C. albicans gene MBF1 in virulence and ability to colonize internal organs of mammalian and insect hosts. MBF1 encodes a putative transcriptional regulator, and as such it likely has an impact in the regulation of C. albicans gene expression during host infection. Here, recent advances in RNA-seq technologies were used to obtain a detailed analysis of the impact of MBF1 on C. albicans gene expression both in vitro and during infection. MBF1 was involved in the regulation of several genes with a role in glycolysis and response to stress, particularly to nutritional stress. We also investigated whether an interaction existed between MBF1 and GCN4, a master regulator of response to starvation, and found that both genes were needed for resistance to amino acid starvation, suggesting some level of interaction between the two. Reinforcing this idea, we showed that the proteins encoded by both genes could interact. Consistent with the role of MBF1 in virulence, we also established that GCN4 was necessary for virulence in the mouse model of systemic infection as well as in the Galleria mellonella infection model.

Increasing absorber efficiency in aqueous amine CCS systems is one avenue to decrease capitol cost by reducing the overall size of the absorber column. One potential route to improve the absorber is by replacing conventional steel packing with custom designed packing made from 3D printed polymers. 3D printing offers endless flexibility in packing designs to better enhance liquid/gas contact, increase CO2 mass transfer and create more efficient absorber columns. Before exploring novel packing designs, it is necessary to identify polymer materials that can be 3D printed while also showing long-term physical and surface property stability upon exposure to corrosive amine solutions. Four polymers that are commonly used for 3D printing were evaluated for physical and surface stability during long-term exposure to a corrosive CO2-loaded amine solution at temperatures typically observed in the absorber column. Three polymers, HDPS, ABS and Nylon were found to be physically stable after 3000 hr of amine exposure at temperatures up to 60 °C. The contact angle (wetting) of the polymer surfaces were also stable after exposure to the CO2-loaded amine solution.

Designing new liquids for CO2 absorption is a challenge in CO2 removal. Here, achieving low regeneration energies while keeping high selectivity and large capacity are current challenges. Recent cooperative metal–organic frameworks have shown the potential to address many of these challenges. However, many absorbent systems and designs rely on liquid capture agents. We present herein a liquid absorption system which exhibits cooperative CO2 absorption isotherms. Upon introduction, CO2 uptake is initially suppressed, followed by an abrupt increase in absorption. The liquid consists of a bifunctional guanidine and bifunctional alcohol, which, when dissolved in bis(2-methoxyethyl) ether, forms a secondary viscous phase within seconds in response to increases in CO2. The precipitation of this second viscous phase drives CO2 absorption from the gas phase. The isotherm of the bifunctional system differs starkly from the analogous monofunctional system, which exhibits limited CO2 uptake across the same pressure ...

For widespread adoption of carbon capture and storage to fight climate change, major reductions in both the energy use and capital cost of carbon capture are needed. Many purpose-designed, water-lean solvents have recently been developed to improve the energy-efficiency of carbon capture. These solvents, including ionic liquids (ILs), have shown promise for substantially lower energy demand in post-combustion capture but have drawbacks like high viscosity and solid precipitates. Micro-encapsulation is a technique where a solvent is encased in small (∼500 μm diameter), spherical shells of a CO2-permeable polymer, greatly increasing the reactive surface area of the solvent and safely containing solid precipitates. Here, we show the kinetics of an IL are enhanced by microencapsulation. The kinetics of the IL in liquid and encapsulated form are compared with those for sodium carbonate solution and the cases where the capsule shell material limits mass transfer are identified. Finally, we make the first demonstration of microencapsulated CO2 solvents in a flow-through, fixed bed reactor. CO2 absorption rates are broadly in agreement with static CO2 absorption measurements made previously.

Carbon black nanoparticles (CB) were covalently modified to improve the photothermal regeneration of a CO2 capture nanofluid through decarboxylation. The photothermal release of CO2 addresses high energy costs associated with regenerating capture fluids. By incorporating sulfonamides on the surface of CB, we enhance the photothermal separation of CO2 from MEA by approximately 70% more than the unmodified CB. In contrast, with an anionic sulfonate on the surface, the total CO2 released fell by approximately 60%. We verified the chemical composition and structure of surface modification using complementary techniques including FT-IR, TGA, XPS, and Raman spectroscopy.

Natural systems employ microvascular exchangers with circular packing for both heat and mass transfer that closely conform to the compact, packing of circles of two diameter. Mathematical descriptions of these systems exist, but have rarely been studied in three dimensions for their exchange properties. We focus on four close packed patterns: “Hexagonal” “Dodecagonal”, “Squarer”, and “Double Squarer”. While two of these patterns have natural analogs, the others are abiological. We compare computationally and experimentally the mass and heat transfer characteristics of these various patterns. Intriguingly the “Double Squarer” pattern, had the highest transfer rates within our fabrication constraints.

Here we report the investigation of controlled PbI2 secondary phase formation in CH3NH3PbI3 (MAPI) photovoltaics through post-deposition thermal annealing, highlighting the beneficial role of PbI2 on device performance. Using high-resolution transmission electron microscopy we show the location of PbI2 within the active layer and propose a nucleation and growth mechanism. We discover that during the annealing that PbI2 forms mainly in the grain boundary regions of the MAPI films and that at certain temperatures the PbI2 formed can be highly beneficial to device performance – reducing current–voltage hysteresis and increasing the power conversion efficiency. Our analysis shows that the MAPI grain boundaries as susceptible areas that, under thermal loading, initiate the conversion of MAPI into PbI2.

Purpose-designed, water-lean solvents have been developed to improve the energy efficiency of CO2 capture from power plants, including CO2-binding organic liquids (CO2BOLs) and ionic liquids (ILs). Many of these solvents are highly viscous or change phases, posing challenges for conventional process equipment. Such problems can be overcome by encapsulation. Micro-Encapsulated CO2 Sorbents (MECS) consist of a CO2-absorbing solvent or slurry encased in spherical, CO2-permeable polymer shells. The resulting capsules have diameters in the range of 100–600 μm, greatly increasing the surface area and CO2 absorption rate of the encapsulated solvent. Encapsulating these new solvents requires careful selection of shell materials and fabrication techniques. We find several common classes of polymers are not compatible with MECS production, but we develop two custom formulations, a silicone and an acrylate, that show promise for encapsulating water-lean solvents. We make the first demonstration of an encapsulated IL for CO2 capture. The rate of CO2 absorption is enhanced by a factor of 3.5 compared to a liquid film, a value that can be improved by further development of shell materials and fabrication techniques.

For reducing anthropogenic CO2 emissions, carbon capture and sequestration technologies benefit from the creation of new and efficient gas exchange systems. Vascularized systems provide a means of exchanging CO2 by providing high specific surface areas and patterned, intimate contact between capture fluids and gases. The well-defined geometrical arrangement of fluid and gas channels, separated by semipermeable membranes, also provides a new platform for augmenting the function of liquid chemical solutions to carbon capture. In particular, the separation distance of the channels, or polymer membrane thickness, is closely related to the absorption rate as gases must permeate through the membrane before reacting with a fluid. Here, a study of the relationship between the membrane thickness in 3D microvascular contactors and absorption rates via a selective etching process is reported. By decreasing the membrane thickness, the mass transport rate of CO2 in the vascular contactor is increased by up to 160%.

Vascular endothelial growth factor receptor (VEGFR) or vascular endothelial growth factor (VEGF) inhibitors have shown only modest clinical activity for most tumor types when used as single agents. However, present evidence indicates that these antiangiogenic drugs can cause transient "normalization" of the tumor vasculature, thereby improving the delivery of systemic chemotherapy. We examined temporal changes in tumor vascular function in response to the novel VEGFR2 inhibitor, SKLB1002. Established tumor-bearing animals were evaluated at serial time points for treatment-associated changes in tumor vascular architecture and function. As a result, blocking VEGF signaling by SKLB1002 produced a morphologically and functionally "normalized" vascular network. Consistent with our observations, a 2.2 fold increase in intratumoral doxorubicin levels was determined with SKLB1002 pretreatment compared with administration of doxorubicin alone. Finally, combined SKLB1002 and doxorubicin exhibited significant antitumor (49% of control size) and antimetastatic effects (12% of control metastatic nodules) in vivo. Our results showed SKLB1002 induced vascular normalization and enhanced anticancer drug delivery, which were associated with the observed synergistic effect in vivo.

Silicone elastomers have broad versatility within a variety of potential advanced materials applications, such as soft robotics, biomedical devices, and metamaterials. A series of custom 3D printable silicone inks with tunable stiffness is developed, formulated, and characterized. The silicone inks exhibit excellent rheological behavior for 3D printing, as observed from the printing of porous structures with controlled architectures. Herein, the capability to tune the stiffness of printable silicone materials via careful control over the chemistry, network formation, and crosslink density of the ink formulations in order to overcome the challenging interplay between ink development, post-processing, material properties, and performance is demonstrated.

Despite major interest in sodium iron (III) ethylenediaminetetraacetic acid's (EDTA) potential use in food fortification programs in potentially curbing the global problem of iron deficiency and its anemia, synthesis methods of stable isotope-labeled sodium iron (III) EDTA for use in human bioavailability studies are incomplete, incorrect or totally lacking. Owing to a number of clinical research groups requiring this compound in bioavailability studies, in both developing and already developed countries, we simplified and optimized the synthesis of sodium iron (III) EDTA from a block of isotopically enriched iron metal, in order that it be easily reproduced, cheaply, using simple basic laboratory apparatus. The resulting product is of high purity (>99.0%), and may be used for human stable isotope bioavailability studies. The simplicity of this method allows for the many research groups, currently doing such studies, to perform their own syntheses. Additionally, more uniformity in this synthesis will reduce the variation observed between such studies.

We report a technique to coat polymers onto 3D surfaces distinct from traditional spray, spin, or dip coating. In our technique, the surface of a template structure composed of poly(lactic acid) swells and entraps a soluble polymer precursor. Once entrapped, the precursor is cured, resulting in a thin, conformal membrane. The thickness of each coating depends on the coating solution composition, residence time, and template size. Thicknesses ranged from 400 nm to 4 μm within the experimental conditions we explored. The coating method was compatible with a range of polymers. Complicated 3D structures and microstructures of 10 μm thickness and separation were coated using this technique. The templates can also be selectively removed, leaving behind a hollow membrane structure in the shape of the original printed, extruded, or microporous template structures. This technique may be useful in applications that benefit from three-dimensional membrane topologies, including catalysis, separations, and potentially tissue engineering.

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material fabrication techniques are able to mimic the complexity of these structures while maintaining scalability. The Vaporization of a Sacrificial Component (VaSC) process is able to do so. This process uses sacrificial fibers as a template to form hollow, cylindrical microchannels embedded within a matrix. Tin (II) oxalate (SnOx) is embedded within poly(lactic) acid (PLA) fibers which facilitates the use of this process. The SnOx catalyzes the depolymerization of the PLA fibers at lower temperatures. The lactic acid monomers are gaseous at these temperatures and can be removed from the embedded matrix at temperatures that do not damage the matrix. Here we show a method for aligning these fibers using micromachined plates and a tensioning device to create complex patterns of three-dimensionally arrayed microchannels. The process allows the exploration of virtually any arrangement of fiber topologies and structures.

Computational structure prediction methods based on learning are poorly tractable for transmembrane β-barrel (TMB) proteins, for it is difficult to observe them with standard experimental techniques. Generally, those structures are not only a series of β-strands where each is bonded to the preceding and succeeding ones in the primary sequence, but they may contain Greek key or Jelly roll motifs as well. This may be described as a permutation on the order of the bonded segments. We model the protein folding problem with minimum energy into the search of the longest closed path in a weighted graph with respect to a given permutation. With dynamic programming, the algorithm runs in O(N2) for an identity permutation, and at most O(N4) for the Greek key motifs, where N is the number of amino acids. The prediction accuracy as well as the discrimination ability is favorably comparable with existing works.

A perspective is provided of the infrared‐active fundamental mode ν3 and the band structure of its overtones relevant for uranium hexafluoride. The treatment is based on nonlinear (Morse‐type) creation and annihilation operators. The spectrum generating algebra provides ready access to anharmonic spectral features which incorporate dissociation characteristics.

We report on the fabrication of an ultra-high aspect ratio ionically conductive single microchannel with tunable diameter from ≈ 20 μm to fully closed. The 4 mm-long channel is fabricated in a Polydimethylsiloxane (PDMS) mold and its cross-sectional area is controlled by applying macroscopic compressive strain to the mold in a direction perpendicular to the channel length. We investigated the ionic conduction properties of the channel. For a wide range of compressive strain up to ≈ 0.27, the strain dependence of the resistance is monotonic and fully reversible. For strain > 0.27, ionic conduction suddenly shuts off and the system becomes hysteretic (whereby a finite strain reduction is required to reopen the channel). Upon unloading, the original behavior is retrieved. This reversible behavior is observed over 200 compression cycles. The cross-sectional area of the channel can be inferred from the ion current measurement, as confirmed by a Nano-Computed Tomography investigation. We show that the cross-sec...

An improved method for the radiosynthesis of [ 123 I]melatonin is presented. The suitability of several oxidizing agents, such as Iodo-Gen, chloramine-T, hydrogen peroxide and in situ generated peracetic acid were evaluated for the oxidative radioiodination reactions. The rates at which reactions progressed as well as the radiochemical yields and purities were compared. Peracetic acid proved to be the superior oxidizing agent, producing an average radiochemical yield of 70 ± 10% after 40 min reaction time, and causing less degradation of the melatonin molecule than Iodo-Gen or chloramine-T.

The effect of cooperative action of pairs of affiliated muons on the fusion of hydrogen nuclear isotopes is discussed. The dt{sub {mu}{mu}} fusion rate is found to be enhanced more than ten-fold relative to the single muon induced rate.

In order to select a reliable routine analytical procedure for the extraction and estimation of inorganic N in South African soils three steam distillation procedures were compared. With the one procedure the soil sample is shaken with 2,0 ? KCl for one hour and the extract is then analyzed by distillation. With the other two procedures the soil sample is distilled directly with either 2,0 ? KCl or distilled H20, eliminating the extraction step. The three procedures yield results for NH4 +‐N and N03 ‐‐N which can be regarded as identical for all practical purposes. It may be recommended with confidence that one of the direct distillation procedures be employed for routine soil analyses.

The finding of low plasma pyridoxal-5'-phosphate levels in patients suffering from myocardial infarction has been construed as possible evidence for the pathogenetic role that vitamin B6 deficiency may play in causing premature ischaemic heart disease. However, the presence of normal plasma pyridoxal-5'-phosphate levels in patients with angiographic evidence of coronary artery narrowing but with no previous infarctions prompted the investigation of possible short-term alterations in plasma pyridoxal-5'-phosphate levels during the acute phase of myocardial infarction. In the follow-up of 30 patients with acute myocardial infarction, all of them showed a continuous decrease of approximately 45% in plasma pyridoxal-5'-phosphate levels during the acute phase. These levels subsequently returned back to normal before discharge from hospital. A large number of volunteers from an ethnic group known to have a very low incidence of ischaemic heart disease were found to have both significantly lower total cholesterol and plasma pyridoxal-5'-phosphate levels than a Caucasian group in the same geographic area which is known to have a high incidence of ischaemic heart disease. These findings therefore do not support the contention that vitamin B6 deficiency may be a risk index for ischaemic heart disease.

The objective of this investigation was to compare the susceptibility of different ammonium containing and forming fertilizers to NH3 losses and to determine the effect of application rates on NH3 volatilization. Losses of NH3 from five fertilizers, namely (NH4)2SO4, CAN, urea, MAP and DAP were determined. The fertilizers were surface-applied to a sandy clay loam Arniston soil and a clayey Gelykvlakte soil of which the pH values were respectively 9.0 and 8.9. The application levels were equivalent to 0, 15, 30, 60, 120 and 240 kg N ha−1. After a contact period of 3 days NH3 losses were determined. Ammonia was lost from both soils under all treatments. More NH3 was lost from the clayey Gelykvlakte soil compared with the sandy clay loam Arniston soil. Loss of NH3 from the various fertilizers was ranked as follows: Urea > DAP > (NH4)2SO4 > MAP > CAN. Ammonia losses increased with increasing application rates, but the proportion of N lost, decreased. Losses of NH3 may be reduced by selective choice of fertilizer type and application rate.

Comparison of ammonium sulphate, ammonium nitrate and urea under irrigation conditions on two soils from the Vaalharts Irrigation Scheme. On a sandy soil with 9% clay in the B21 horizon, ammonium sulphate gave higher wheat yields than limestone ammonium nitrate and urea. On a sandy loam soil with 20% clay in the B21 horizon, there was no difference between the nitrogen sources. Leaching studies in soil columns indicated that virtually no ammonium nitrogen was leached from these soils. Nitrate leaching was considerable and much higher from the sandy ammonium to nitrate is apparently slow in these soils, because significant leaching of nitrate from ammonium sulphate treatment was only evident at the third leaching. Leaching losses of nitrogen were consequently much smaller in the case of ammonium sulphate than in the case of ammonium nitrate.

Ammonia volatilization from five soils, ranging in clay content from 7,6 to 49,9%, were determined after pH values of the soils were adjusted to 8,0. Ammonium sulphate, limestone ammonium nitrate, urea, monoammonium phosphate and diammonium phosphate were applied on the soil surface at levels equivalent to 0,15, 30, 60,120 and 240 kg N ha−1. After a contact period of three days ammonia losses were determined. Ammonia was lost from all soils under all treatments, losses increasing with increasing levels of application. Loss of ammonia from the various fertilizers was ranked as follows: LAN < MAP < (NH4)2)SO4 < DAP < urea. Surprisingly, ammonia losses increased with an increase in clay content or cation exchange capacity of the soil. The apparently anomalous role of the cation exchange complex of the soils to ammonia volatilization can be ascribed to the buffer capacity of the soils. An explanation for the volatilization mechanism is proposed. S. Afr. J. Plant Soil 1986, 3: 31–34

A laboratory study was conducted into the effects of the treatment of activated sludge effluent with different oxidants on the biodegradability of the organic substances. It was found that, under the experimental conditions described, ozone increased the biodegradability, whereas chlorine had no apparent significant effect. The effect of continuous oxidative pretreataent of activated sludge effluent on microbial populations and the biological activated carbon used subsequently in the process also was studied. It was found that ozone, particularly at a dosage of about 5 mg/L promoted biological activity, while chlorine and oxygen (in addition to the dissolved oxygen already in the effluent) had no significant effect on the biological population size.

Movement of NH3 plus NH4 + from nitrogen fertilizers, band placed either as crystals or as granules in alkaline soils, was determined. The pH values of these soils, whereof the clay contents ranged from 7,6 to 49,9%, were adjusted to approximately 8,8. Fertilizers like (NH4)2SO4, LAN, urea, MAP and DAP were band placed in these soils with different water contents at different bulk densities. The application level was equivalent to 60 kg N ha−1. After a contact period of 14 days the movement of NH3 plus NH4 + was determined. The distances that NH3 plus NH4 + moved from the plane of application varied between 45 and 100 mm. The results indicate that the movement of NH4 + was small compared to the movement of NH3. The major factor that controlled the degree of NH3 movement in soil was the quantity of NH4 + converted to NH3. The conversion of NH4 + to NH3 was governed by the variable soil properties and the type of fertilizer. Both diffusion and convection contributed to the movement of NH3.

The objective of this investigation was to compare different application methods whereby ammonia losses from nitrogen fertilizers can be limited when applied to alkaline soils. Three application methods were simulated, namely broadcasting, ploughing under and band placement. Five nitrogen fertilizers, namely (NH4)2SO4, LAN, urea, MAP and DAP were applied at a rate of 120 kg N ha-1 to five soils which ranged in clay content between 7,6 and 49,9%. The pH(H2O) of the soils was adjusted to approximately 8,8. After a contact period of 14 days significant losses of NH3 occurred when the fertilizers were broadcast, compared with simulated ploughing under and the band placement. The depth of application which is sufficient to limit ammonia loss in a specific case, depends on the concentration of NH3 present in the soil solution and the diffusion of NH3 to the soil surface. Knowing the properties of the fertilizers and of the soil an appropriate combination of fertilizer and application method may be chosen to lim...

Studies were undertaken to obtain preliminary information on the availability of Zn sorbed by hydrated Fe oxides as a source of Zn for plants. The results presented suggest that Zn bound to hydrated Fe oxides in soils, through the medium of polyvalent phosphate ions, is unavailable to plants. In the absence of phosphate ions, only the more strongly-crystalline hydrated Fe oxides, such as goethite, fix Zn against plant uptake.

A rapid procedure developed for the preliminary purification of soil extracts and plant digests preceding the polarographic determination of zinc is described. The procedure meets the necessary requirements of precision and when used in conjunction with the polarographic procedure described by Barrows and Drossdoff (1960), proved desirable for routine analysis involving large numbers of soil or plant samples.

Most preparations of infectious virus nucleic acids retain only about 0.1% or less of the infectivity of the original virus material. This is not necessarily the result of destruction of much of the intact nucleic acid during chemical procedures, but may be due to the insensitivity of the assay methods employed (Holland et al. 1961; Tovell & Colter, 1967). For the titration of infectious DNA obtained from polyoma virus, one of the methods in current use requires the direct plating of DNA in 0.55 m-NaCl on the monolayers of mouse embryo cells (Weil, 1961). This procedure has the disadvantage that the cell damage caused by the hypertonic NaCl renders accurate plaque counts difficult. A more recently described method (Warren & Thorne, 1968) avoids this complication by infecting monolayers in the presence of diethylaminoethyldextran (DEAE-dextran) in an isotonic medium.

IN a recent communication, Polson1 indicated that the small animal viruses fall into definite weight-groups as calculated from their sedimentation constants, using the usual assumptions regarding density and particle shape. The particle weights are multiples of 1, 4, 16 and 64 of a basic unit, 12 mµ in diameter. Soluble antigen which itself is non-infective has been recovered from tissues infected with a variety of virus. It is of particular interest that those soluble antigens which have been measured are all approximately 12 mµ in diameter (influenza2, rabies3 and African horsesickness virus4).

Electron correlations in doubly excited s‐state they are discussed, in accordance with the results reported by Herrick, Kellman and Polak.