Synthesis,characterization and acidochromism of Poly (2-<Emphasis Type="Italic">N,N</Emphasis>–dimethylamino-4,6-Bis (2-thienyl)-pyrimidine)

A new monomer (2-N,N-dimethylamino-4,6-Bis (2-thienyl)–pyrimidine) was synthesized and its homopolymer was successfully prepared by using Ferric trichloride (FeCl₃) as an oxidant. The structure of the polymer and monomer was fully characterized by ¹H–NMR, FTIR, UV-vis, Fluorescent spectroscopy and X-ray diffraction pattern. The polymer gives rise to a band at λ _max = 391 nm. The polymer showed the PL spectrum, gave a peak at 507 nm.We have observed that the polymer was sensitive to inorganic acids and the acidochromism behavior was investigated applying organic acid such as CF₃COOH. The corresponding UV-Vis peaks were observed at 464 nm and 357 nm respectively. X-ray diffraction data shows that polymer has a certain crystallinity. The polymer exhibited an [η] value of 0.26 dLg⁻¹ at 25 °C in H₂SO₄ (w = 98%).     

Effects of phenyl-based pendent groups on helical conformation of poly(<Emphasis Type="Italic">N</Emphasis>-propargylamides)

Five achiral N-propargylamide monomers with various phenyl-based substitutents, [HC ≡ CCH₂NHCOR, R for M1: C₆H₄CH₃; M2: C₆H₄CH₂CH₃; M3: C₆H₄(CH₂)₂CH₃; M4: C₆H₄(CH₂)₃CH₃; M5: C₆H₄C(CH₃)₃], were synthesized and polymerized with a rhodium catalyst, (nbd)Rh⁺B^-(C₆H₅)₄ (nbd = 2,5-norbornadiene). The corresponding five homopolymers were obtained in high yields of 90–95% and with moderate molecular weights (M _n ≥ 10 000). All the polymers possessed high cis contents (≥95%). Poly(1)–poly(3) exhibited UV-vis absorption peaks at approx. 350 nm, which indicates that the three polymers formed helical conformations, while no UV-vis absorption peaks could be observed in poly(4) and poly(5) in the wavelength range of 320–500 nm, demonstrating that these two polymers could not adopt helical structures under the examined conditions. To confirm the helical structures formed in poly(1)–poly(3), a chiral monomer, M6, was utilized to copolymerize with M2, which was used as the representative for M1−M3. M6 was utilized since its polymer could form stable helices under suited conditions. The resulting copolymers exhibited remarkable CD effects, however, the maximum wavelength in the copolymers varied remarkably, mainly depending on the composition of the copolymers. It is concluded that in the formation of ordered helical conformations, the substitutents of varied bulk led to different steric repulsion and varied synergic effects among the neighboring pendent groups.     

Synthesis and characterization of a new NLO-active donor–acceptor-type conjugated polymer derived from 3,4-diphenylthiophene

A new donor–acceptor-type conjugated polymer (P1) carrying 3,4-diphenylthiophene, 2,5-dihexyloxybenzene, and 1,3,4-oxadiazole units was synthesized through multistep reactions. The polymer was prepared using a polyhydrazide precursor route. The polymer has a well-defined structure and exhibits good thermal stability, with a decomposition onset temperature in nitrogen of 300 °C. Cyclic voltammetry experiments revealed that the polymer has low-lying LUMO (−3.68 eV) and high-lying HOMO (−5.78 eV) energy levels. The electrochemical band gap was found to be 2.10 eV. The UV-visible absorption spectrum of the polymer presented a maximum at 373 nm, and it displayed bluish-green fluorescence in dilute chloroform solution. The nonlinear optical properties of the new polymer were investigated at 532 nm using the Z-scan technique with nanosecond laser pulses. The polymer exhibited strong optical limiting behavior due to excited state absorption, which was phenomenologically similar to a three-photon absorption (3PA) process. The 3PA coefficient γ was found to be 7 × 10⁻²² m³/W². The studies show that the new polymer (P1) is a promising material for developing efficient photonic devices.     

Nitrous oxide emissions from fertilized and unfertilized grasslands on peat soil

Emissions of nitrous oxide (N₂O) from managed and grazed grasslands on peat soils are amongst the highest emissions in the world per unit of surface of agriculturally managed soil. According to the IPCC methodology, the direct N₂O emissions from managed organic soils is the sum of N₂O emissions derived from N input, including fertilizers, urine and dung of grazing cattle, and a constant ‘background’ N₂O emission from decomposition of organic matter that depends on agro-climatic zone. In this paper we questioned the constant nature of this background emission from peat soils by monitoring N₂O emissions, groundwater levels, N inputs and soil NO₃ ⁻–N contents from 4 grazed and fertilized grassland fields on managed organic peat soil. Two fields had a relatively low groundwater level (‘dry’ fields) and two fields had a relatively high groundwater level (‘wet’ fields). To measure the background N₂O emission, unfertilized sub-plots were installed in each field. Measurements were performed monthly and after selected management events for 2 years (2008–2009). On the managed fields average cumulative emission equaled 21 ± 2 kg N ha⁻¹y⁻¹ for the ‘dry’ fields and 14 ± 3 kg N ha⁻¹y⁻¹ for the ‘wet’ fields. On the unfertilized sub-plots emissions equaled 4 ± 0.6 kg N ha⁻¹y⁻¹ for the ‘dry’ fields and 1 ± 0.7 kg N ha⁻¹y⁻¹ for the ‘wet’ fields, which is below the currently used estimates. Background emissions were closely correlated with groundwater level (R ² = 0.73) and accounted for approximately 22% of the cumulative N₂O emission for the dry fields and for approximately 10% of the cumulative N₂O emissions from the wet fields. The results of this study demonstrate that the accuracy of estimating direct N₂O emissions from peat soils can be improved by approximately 20% by applying a background emission of N₂O that depends on annual average groundwater level rather than applying a constant value.     

Conjugated opto/electroactive ethynylene-carbazole polymers with TTF as pendant group

Three conjugated ethynylene-carbazole polymers with Tetrathiafulvalene (TTF) as pendant group (P1–P3) were synthesized by using sonogashira coupling reaction and characterized by ¹H NMR, GPC, CV, UV–Vis, FL, and TGA. CV and UV–Vis spectra showed that an intramoleular interaction existed between the electron-rich moiety TTF and electron-deficient moiety polyethynylcarbazole of the polymers. A strong fluorescence quench (ca. 99%) could be observed, compared to the polyethynylene-carbazole without TTF units, which could be ascribed to the photo-induced electron transfer (PET) interaction from TTF moiety to the polyethynylene-carbazole backbone. The observed onset decomposition temperatures (T _d) for P1–P3 varied from 256 to 298 °C. The polymers mentioned above exhibited good thermal properties and higher conductivity (neutral conductivity ~7–11 × 10⁻⁷ S cm⁻¹; doped conductivity ~6–11 × 10⁻⁴ S cm⁻¹).     

Emissions of N<Subscript>2</Subscript>O from fertilized and grazed grassland on organic soil in relation to groundwater level

Intensively managed grasslands on organic soils are a major source of nitrous oxide (N₂O) emissions. The Intergovernmental Panel on Climate Change (IPCC) therefore has set the default emission factor at 8 kg N–N₂O ha⁻¹ year⁻¹ for cultivation and management of organic soils. Also, the Dutch national reporting methodology for greenhouse gases uses a relatively high calculated emission factor of 4.7 kg N–N₂O ha⁻¹ year⁻¹. In addition to cultivation, the IPCC methodology and the Dutch national methodology account for N₂O emissions from N inputs through fertilizer applications and animal urine and faeces deposition to estimate annual N₂O emissions from cultivated and managed organic soils. However, neither approach accounts for other soil parameters that might control N₂O emissions such as groundwater level. In this paper we report on the relations between N₂O emissions, N inputs and groundwater level dynamics for a fertilized and grazed grassland on drained peat soil. We measured N₂O emissions from fields with different target groundwater levels of 40 cm (‘wet’) and 55 cm (‘dry’) below soil surface in the years 1992, 1993, 2002, 2006 and 2007. Average emissions equalled 29.5 kg N₂O–N ha⁻¹ year⁻¹ and 11.6 kg N–N₂O ha⁻¹ year⁻¹ for the dry and wet conditions, respectively. Especially under dry conditions, measured N₂O emissions exceeded current official estimates using the IPCC methodology and the Dutch national reporting methodology. The N₂O–N emissions equalled 8.2 and 3.2% of the total N inputs through fertilizers, manure and cattle droppings for the dry and wet field, respectively and were strongly related to average groundwater level (R ² = 0.74). We argue that this relation should be explored for other sites and could be used to derive accurate emission data for fertilized and grazed grasslands on organic soils.     

Erratum to: Long-term tillage,straw and N rate effects on quantity and quality of organic C and N in a Gray Luvisol soil

Long-term use of soil, crop residue and fertilizer management practices may affect some soil properties, but the magnitude of change depends on soil type and climatic conditions. Two field experiments with barley, wheat, or canola in a rotation on Gray Luvisol (Typic Cryoboralf) loam at Breton and Black Chernozem (Albic Argicryoll) loam at Ellerslie, Alberta, Canada, were conducted to determine the effects of 19 or 27 years (from 1980 to 1998 or 2006 growing seasons) of tillage (zero tillage [ZT] and conventional tillage [CT]), straw management (straw removed [S_Rem] and straw retained [S_Ret]) and N fertilizer rate (0, 50 and 100 kg N ha⁻¹ in S_Ret, and 0 kg N ha⁻¹ in S_Rem plots) on pH, extractable P, ammonium-N and nitrate–N in the 0–7.5, 7.5–15, 15–30 and 30–40 cm or 0–15, 15–30, 30–60, 60–90 and 90–120 cm soil layers. The effects of tillage, crop residue management and N fertilization on these chemical properties were usually similar for both contrasting soil types. There was no effect of tillage and residue management on soil pH, but application of N fertilizer reduced pH significantly (by up to 0.5 units) in the top 15 cm soil layers. Extractable P in the 0–15 cm soil layer was higher or tended to be higher under ZT than CT, or with S_Ret than S_Rem in many cases, but it decreased significantly with N application (by 18.5 kg P ha⁻¹ in Gray Luvisol soil and 20.5 kg P ha⁻¹ in Black Chernozem soil in 2007). Residual nitrate–N (though quite low in the Gray Luvisol soil in 1998) increased with application of N (by 17.8 kg N ha⁻¹ in the 0–120 cm layer in Gray Luvisol soil and 23.8 kg N ha⁻¹ in 0–90 cm layer in Black Chernozem soil in 2007) and also indicated some downward movement in the soil profile up to 90 cm depth. There was generally no effect of any treatment on ammonium-N in soil. In conclusion, elimination of tillage and retention of straw increased but N fertilization decreased extractable P in the surface soil. Application of N fertilizer reduced pH in the surface soil, and showed accumulation and downward leaching of nitrate–N in the soil profile.     

Preparation of Transparent PVC-Titanosilicate Nanocomposites by Interlamellar Silylation of Layered Titanosilicate

The preparation and structural characterization of a transparent poly(vinyl chloride)–octyltriethoxysilane-Jilin Davy Faraday-Layered solid #1 nanocomposite is reported. H⁺-Jilin Davy Faraday-Layered solid #1 (H₄Ti₂Si₈O₂₂) was prepared by proton exchange of layered Na⁺-Jilin Davy Faraday-Layered solid #1 (Na₄Ti₂Si₈O₂₂). The octyltriethoxysilane-Jilin Davy Faraday-Layered solid #1, in a siloxane-pillared form, was obtained by hydrolysis of the H⁺-Jilin Davy Faraday-Layered solid #1–dodecylamine–octyltriethoxysilane in pure water. In addition, the poly(vinyl chloride)–octyltriethoxysilane-Jilin Davy Faraday-Layered #1, as an organic–inorganic nanocomposite, was prepared using a poly(vinyl chloride) resin and Na⁺-Jilin Davy Faraday-Layered solid #1, H⁺-Jilin Davy Faraday-Layered solid #1 or octyltriethoxysilane-Jilin Davy Faraday-Layered #1 in tetrahydrofuran. The prepared organic–inorganic nanocomposite, as an interlayer space expander, was confirmed by XRD, SEM, EDS, TGA and TEM. The poly(vinyl chloride)–octyltriethoxysilane-Jilin Davy Faraday-Layered #1 nanocomposite showed a larger interlayer distance (~6.74 nm) than octyltriethoxysilane-Jilin Davy Faraday-Layered solid #1 (2.95 nm), H⁺-Jilin Davy Faraday-Layered solid #1 (0.92 nm) and Na⁺-Jilin Davy Faraday-Layered solid #1 (1.08 nm).     

Synthesis,characterization, and properties of co-poly(ether–urethane–urea)s containing lariat cryptand 22: Li<Superscript>+</Superscript> harvesting polymers

In this work, some segmented poly(ether–urethane–urea)s (PEUUs) containing aza crown ether (cryptand) were prepared and characterized. These polymers were synthesized via the reaction of kryptofix 22 with 2 mol excess of 4,4′-methylene-bis-(4-phenylisocyanate) (MDI), and different molecular weights of polyethylene glycols (PEGs). Morphology, thermal, and complexation properties of these polymers were studied by Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), atomic absorption spectroscopy (AAS), and solid state NMR (S-NMR). The data confirmed complexation ability of these polymers for Li⁺ ion absorption and revealed the effect of Li⁺ ion complexation on the morphology and thermal behavior of the PEUUs.     

Synthesis,characterization, and OFET characteristics of 3,4-diaryl substituted poly(thienylene vinylene) derivatives

Poly(thienylene vinylene) derivatives bearing aryl substituents at 3,4-positions have been synthesized in good yield by Stille-type polycondensation. Two types of aryl substituents, either a 4-octylphenyl or a 5-octyl-2-thienyl, were investigated in this study. The polymers were characterized by ¹H NMR, GPC, TGA, UV–vis absorption, and photoluminescence spectroscopy. The polymers (P1–P4) showed good to excellent solubility in common organic solvents, and UV–vis absorption spectra in solution exhibit maxima in the range of 511–595 nm. GPC analysis using PPP standards showed a number average molecular weight range of 6.59–8.98 × 10³ g mol⁻¹ for the various polymers. The field effect transistors based on these polymers were studied, and the results obtained are correlated to their molecular structure.     

Amine-terminated aromatic and semi-aromatic hyperbranched polyamides: synthesis and characterization

A facile synthetic approach to aromatic and semiaromatic amine-terminated hyperbranched polyamides via direct polymerization of triamine (B₃) with different diacid chlorides (A₂) was explored. An aromatic triamine, 1,3,5-tris(4′-aminophenylcarbamoyl)benzene (TAPCB), was synthesized and monomers were characterized by elemental analysis, FTIR, ¹H and ¹³C NMR spectroscopy. Finally, the polycondensation reaction of TAPCB with terephthaloyl chloride (TPC), isophthaloyl chloride (IPC), sebacoyl chloride (SC) and adipoyl chloride (AC) resulted in the preparation of four hyperbranched polyamides i.e., HBPA 1, 2, 3 and 4, respectively. FTIR and ¹H NMR analyses confirmed the structures of the ensuing polymers and DB was found between 0.51–0.55. These thermally stable amorphous HBPAs were soluble in polar aprotic solvents at room temperature having glass transition temperatures (T_g) between 138–198 °C. Inherent viscosities (η_inh) and weight average molecular weights (M_w) were in the range of 0.27–0.35 dL/g and 1.3 × 10⁴–2.7 × 10⁴, respectively. Future prospects are envisaged.     

Synthesis and characterization of the novel inimer-containing fluorene units and preparation of blue light-emitting polymers

The novel inimer-containing fluorene units was successfully synthesized and characterized. Hyperbranched homopolymer and copolymers with methyl methacrylate (MMA) were prepared by the novel inimer via atom transfer radical polymerization where CuBr/1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) were used as catalyst. The copolymerization of inimer and MMA was performed under different ratio of the initial inimer/MMA and the inimer acted as not only the branched point (BP) but also the functional groups which emit blue light. The number-average molecular weight (M _n) and polydispersity index (PDI) of polymers are in the ranges (3.6–18.4) × 10³ and (1.3–2.8), respectively. Thermal gravimetric analysis (TGA) results showed all polymers had good thermal stabilities. The number of the inimers acted as branched point in the copolymer backbone is estimated by ¹H NMR spectra and UV–Vis absorption spectra.     

Nitrogen in soils,plants, surface water and shallow groundwater in a bahiagrass pasture of Southern Florida,USA

Despite substantial measurements using both laboratory and field techniques, little is known about the spatial and temporal variability of nitrogen (N) dynamics across the landscapes, especially in agricultural landscapes with cow–calf operations. This study was conducted to assess the comparative levels of total inorganic nitrogen, TIN (NO₃–N + NH₄–N) among soils, forage, surface water and shallow groundwater (SGW) in bahiagrass (Paspalum notatum, Flueggé) pastures. Soil samples were collected at 0–20, 20–40, 40–60, and 60–100 cm across the pasture’s landscape (top slope, TS; middle slope, MS; and bottom slope, BS) in the spring and fall of 2004, 2005 and 2006, respectively. Bi-weekly (2004–2006) groundwater and surface water samples were taken from wells located at TS, MS, and BS and from the run-off/seepage area (SA). Concentrations of NH₄–N, NO₃–N, and TIN in SGW did not vary with landscape position (LP). However, concentrations of NH₄–N, NO₃–N, and TIN in water samples collected from the seep area were significantly (P ≤ 0.05) higher when compared to their average concentrations in water samples collected from the different LP. Average concentrations of NO₃–N (0.4–0.9 mg l⁻¹) among the different LP were well below the maximum, of 10 mg l⁻¹, set for drinking water. The maximum NO₃–N concentrations (averaged across LP) in SGW for 2004, 2005 and 2006 were also below the drinking water standards for NO₃–N. Concentration of TIN in soils varied significantly (P ≤ 0.05) with LP and soil depth. Top slope and surface soil (0–20 cm) had the greatest concentrations of TIN. The greatest forage availability of 2,963 ± 798 kg ha⁻¹ and the highest N uptake of 56 ± 12 kg N ha⁻¹ were observed from the TS in 2005. Both forage availability and N uptake of bahiagrass at the BS were consistently the lowest when averaged across LP and years. These results can be attributed to the grazing activities as animals tend to graze more at the BS. The average low soil test value of TN (across LP and soil depth) in our soils of 10.9 mg kg⁻¹ (5.5 kg N ha⁻¹) would indicate that current pasture management including cattle rotation in terms of grazing days and current fertilizer application (inorganic + feces + urine) for bahiagrass pastures may not have negative impact on the environment.     

Morphological and Electrochemical Properties of Crystalline Praseodymium Oxide Nanorods

Highly crystalline Pr₆O₁₁ nanorods were prepared by a simple precipitation method of triethylamine complex at 500°C. Synthesized Pr₆O₁₁ nanorods were uniformly grown with the diameter of 12–15 nm and the length of 100–150 nm without any impurities of unstable PrO₂ phase. The Pr₆O₁₁ nanorod electrodes attained a high electrical conductivity of 0.954 Scm⁻¹ with low activation energy of 0.594 eV at 850°C. The electrochemical impedance study showed that the resistance of electrode was significantly decreased at high temperature, which resulted from its high conductivity and low activation energy. The reduced impedance and high electrical conductivity of Pr₆O₁₁ nanorod electrodes are attributed to the reduction of grain boundaries and high space charge width.     

Synthesis and characterization of poly(aryl ether ketone)s with fluorinated phenyl in the side chain

New bisphenol monomers, (4-fluorophenyl)hydroquinone (3b) and (3,4-difluoro phenyl)hydroquinone (3c), were synthesized in a two-step synthesis. Poly(aryl ether ketone)s (PAEKs) (4a–c) were derived from these fluorinated bisphenols and nonfluorinated bisphenol—phenylhydroquinone (3a) with 4,4′-diflourobenzophenone via a nucleophilic aromatic substitution polycondensation. The obtained polymers had inherent viscosities of 0.50–0.92 dL/g. Thermal analysis showed that the obtained PAEKs had excellent thermal properties, the glass transition temperatures ranged from 148 to 160 °C, and the temperatures at 5% weight loss (Td₅) were above 527 °C and the temperatures at 10% weight loss (Td₁₀) were above 544 °C in nitrogen. All the polymers showed excellent solubility and could dissolve in common organic solvents, such as DMSO, NMP, DMF, etc. So the films of them were easily cast from their solutions, which possessed good mechanical properties, with tensile strengths of 95.2–104.0 MPa, Young’s moduli of 2.68–3.06 GPa, and elongation at break of 15–32%. Furthermore, the prepared PAEKs displayed low dielectric constants (2.75–2.95 at 1 MHz) and hydrophobic character (contact angles for water: 83.9^o–98.4^o).     

Synthesis and photovoltaic properties of alternative copolymers of benzo[1,2-b:4,5-b′]dithiophene and thiophene

Two conjugated polymers containing benzodithiophene (BDT) unit and the unit of thiophene or thieno[3,2-b]thiophene, P(BDT-T) and P(BDT-TT), were synthesized by Pd-catalyzed Stille coupling method. The UV–Vis absorption, thermal, and electrochemical properties of the two polymers were characterized. Photovoltaic properties of the polymers were studied by using the polymers as donor and PC₇₀BM as acceptor with a weight ratio of polymer: PC₇₀BM of 1:1.5. The power conversion efficiencies of the PSC devices based on P(BDT-T) reached 2.05% with an open-circuit voltage of 0.75 V, a short-circuit current of 4.5 mA cm⁻², and a fill factor of 0.61, under the illumination of AM1.5, 100 mW cm⁻².     

Potential of denitrification and nitrous oxide production from agricultural soil profiles (Seine Basin,France)

The denitrification process and the associated nitrous oxide (N₂O) production in soils have been poorly documented, especially in terms of soil profiles; most work on denitrification has concentrated on the upper layer (first 20 cm). The objectives of this study were to examine the origin of N₂O emission and the effects of in situ controlling factors on soil denitrification and N₂O production, also allowing the (N₂O production)/(NO₃ ⁻–N reduction) ratio to be determined through (1) the position on a slope reaching a river and (2) the depth (soil horizons: 10–30 and 90–110 cm). In 2009 and 2010, slurry batch experiments combined with molecular investigations of bacterial communities were conducted in a corn field and an adjacent riparian buffer strip. Denitrification rates, ranging from 0.30 μg NO₃ ⁻–N g⁻¹ dry soil h⁻¹ to 1.44 μg NO₃ ⁻–N g⁻¹ dry soil h⁻¹, showed no significant variation along the slope and depth. N₂O production assessed simultaneously differed considerably over the depth and ranged from 0.4 ng N₂O–N g⁻¹ dry soil h⁻¹ in subsoils (the 90–110-cm layer) to 155.1 ng N₂O–N g⁻¹ dry soil h⁻¹ in the topsoils (the 10–30-cm layer). In the topsoils, N₂O–N production accounted for 8.5–48.0% of the total denitrified NO₃ ⁻–N, but for less than 1% in the subsoils. Similarly, N₂O-consuming bacterial communities from the subsoils greatly differed from those of the topsoils, as revealed by their nosZ DGGE fingerprints. High N₂O-SPPR (nitrous oxide semi potential production rates) in comparison to NO₃-SPDR (nitrate semi potential reduction rates) for the topsoils indicated significant potential greenhouse N₂O gas production, whereas lower horizons could play a role in fully removing nitrate into inert atmospheric N₂. In terms of landscape management, these results call for caution in rehabilitating or constructing buffer zones for agricultural nitrate removal.     

Copolymerization of 4-cyanophenyl acrylate with methyl methacrylate: synthesis, characterization and determination of monomer reactivity ratios

A novel acrylic monomer, 4-cyanophenyl acrylate (CPA) was synthesized by reacting 4-cyanophenol dissolved in methyl ethyl ketone with acryloyl chloride in the presence of triethylamine as a catalyst. Copolymers of CPA with methyl methacrylate (MMA) at different composition was prepared by free radical solution polymerization at 70 ± 1 °C using benzoyl peroxide as an initiator. The copolymers were characterized by FT-IR, ¹H-NMR and ¹³C-NMR spectroscopic techniques. The solubility tests were checked in various polar and non polar solvents. The molecular weight and polydispersity indices of the copolymers were estimated by using gel permeation chromatography. The glass transition temperature of the copolymers increases with increases MMA content. The thermal stability of the copolymer increases with increases in mole fraction of CPA content in the copolymer. The copolymer composition was determined by using ¹H-NMR spectra. The monomer reactivity ratios determined by the application of linearization methods such Fineman–Ross (r ₁ = 0.535, r ₂ = 0. 0.632), Kelen–Tudos (r ₁ = 0.422, r ₂ = 0.665) and extended Kelen–Tudos methods (r ₁ = 0.506, r ₂ = 0. 0.695).     

Characteristics of a tungsten film electrodeposited in a KF–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–WO<Subscript>3</Subscript> melt and preparation of W–Cu–W three-layered films for heat sink application

A tungsten film of 13 μm in thickness was obtained on a copper substrate by galvanostatic electrolysis at 30 mA cm⁻² for 40 min in a KF–B₂O₃–WO₃ (67:26:7 mol%) melt at 850 °C. By cross-sectional scanning electron microscopy observation and energy dispersive X-ray analysis, the tungsten layer was found to be compact and free from cracks, voids and melt inclusion. The X-ray diffractometry analysis revealed that the phase was α-tungsten, and that (222) plane was significantly oriented parallel to the substrate. By nanoindentation, its hardness was found to be 8.4 GPa, which was larger than that of single crystal tungsten. Its Young’s modulus was measured to be 410 GPa, which was similar with the reported value of single crystal tungsten. Its coefficient of linear thermal expansion and thermal conductivity were 4.5 × 10⁻⁶ K⁻¹ and 178 W m⁻¹ K⁻¹, respectively, which were similar values for the tungsten produced by a conventional powder metallurgy method. Finally, W–Cu–W three-layered films were prepared for a heat sink application. It was confirmed that a three-layered film having a desired coefficient of linear thermal expansion can be prepared easily by this new molten salt method.     

Long-term tillage,straw management and N fertilization effects on quantity and quality of organic C and N in a Black Chernozem soil

Soil, crop and fertilizer management practices may affect the amount and quality of organic C and N in soil. A long-term field experiment (growing barley, wheat, or canola) was conducted on a Black Chernozem (Albic Argicryoll) loam at Ellerslie, Alberta, Canada, to determine the influence of 19 (1980 to 1998) or 27 years (1980 to 2006) of tillage (zero tillage [ZT] and conventional tillage [CT]), straw management (straw removed [S_Rem]and straw retained [S_Ret]) and N fertilizer rate (0, 50 and 100 kg N ha⁻¹ in S_Ret and 0 kg N ha⁻¹ in S_Rem plots) on total organic C (TOC) and N (TON), and light fraction organic C (LFOC) and N (LFON) in the 0–7.5 and 7.5–15 cm or 0–5, 5–10 and 10–15 cm soil layers. The mass of TOC and TON in soil was usually higher in S_Ret than in S_Rem treatment (by 3.44 Mg C ha⁻¹ for TOC and 0.248 Mg N ha⁻¹ for TON after 27 years), but there was little effect of tillage and N fertilization on these parameters. The mass of LFOC and LFON in soil tended to increase with S_Ret (by 285 kg C ha⁻¹ for LFOC and 12.6 kg N ha⁻¹ for LFON with annual rate of 100 kg N ha⁻¹ for 27 years)_, increased with N fertilizer application (by 517 kg C ha⁻¹ for LFOC and 36.0 kg N ha⁻¹ for LFON after 27 years), but was usually higher under CT than ZT (by 451 kg C ha⁻¹ for LFOC and 25.3 kg N ha⁻¹ for LFON after 27 years). Correlations between soil organic C or N fractions were highly significant in most cases. Linear regressions between crop residue C input and soil organic C or N were significant in most cases. The effects of tillage, straw management and N fertilizer on soil were more pronounced for LFOC and LFON than TOC and TON, and also in the surface layers than in the deeper layers. Tillage and straw management had little or no effect on C:N ratios, but the C:N ratios in light organic fractions significantly decreased with increasing N rate (from 20.06 at zero-N to 18.91 at 100 kg N ha⁻¹). Compared to the 1979 results, in treatments that did not receive N fertilizer (CTS_Rem0, CTS_Ret0, ZTS_Rem0 and ZTS_Ret0), CTS_Rem0 resulted in a net decrease in TOC concentration (by 1.9 g C kg⁻¹) in the 0–15 cm soil layer in 2007 (after 27 years), with little or no change in the CTS_Ret0 and ZTS_Rem0 treatments, while there was a net increase in TOC concentration (by 1.2 g C kg⁻¹) in the ZTS_Ret0 treatment. Straw retention and N fertilizer application at 50 and 100 kg N ha⁻¹ rates showed a net positive effect on TOC concentration under both ZT (ZTS_Ret50 by 2.3 g C kg⁻¹ and ZTS_Ret100 by 3.1 g C kg⁻¹) and CT (CTS_Ret50 by 3.5 g C kg⁻¹ and CTS_Ret100 by 1.6 g C kg⁻¹) treatments in 2007 compared to 1979 data. In conclusion, the findings suggest that retention of straw, application of N fertilizer and elimination of tillage would improve soil quality, and this might increase the potential for N supplying power of the soil and sustainability of crop productivity.