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Abstract. To identify the key soil parameters influencing N₂O emission from the wheat-growing season, an outdoor pot experiment with a total of 18 fertilized Chinese soils planted with wheat was conducted in Nanjing, China during the 2000/2001 wheat-growing season. Average seasonal N₂O-N emission for all 18 soils was 610 mg m^-2, ranging from 193 to 1,204 mg m^-2, approximately a 6.2-fold difference between the maximum and the minimum. Correlation analysis indicated that the seasonal N₂O emission was negatively correlated with soil organic C (r²=0.5567, P<0.001), soil total N (r²=0.4684, P<0.01) and the C:N ratio (r²=0.4530, P<0.01), respectively. A positive dependence of N₂O emission on the soil pH (r²=0.3525, P<0.01) was also observed. No clear relationships existed between N₂O emission and soil texture, soil trace elements of Fe, Cu and Mg, and above-ground biomass of the wheat crop at harvest. A further investigation suggested that the seasonal N₂O-N emission (E, mg m^-2) can be quantitatively explained by E=1005-34.2SOC+4.1S_a (R²=0.7703, n=18, P=0.0000). SOC and S_a represent the soil organic C (g kg^-1) and available S (mg kg^-1), respectively.

1.The composition of the inner hinge ligament of the marine bivalve mollusc,Spisula solidissima, is calcium carbonate embedded in a hydrated protein matrix. X-ray diffraction analysis of the decalcified matrix suggests a ß-protein configuration.2.Amino acid analysis indicates more than 62% of the residues are glycine.3.Electron microscopic, X-ray diffraction and polarized light data show the calcium carbonate phase to be single crystals of aragonite, about 1,000 angstroms in diameter, and several thousand angstroms in length. The crystals are oriented with the crystallographic c-axis normal to the visible growth lamellae. The crystallographic a- and b-axes are in random orientation.

The Z band in skeletal muscle has two distinct structural states —a relaxed (small square or ss) form and a maximally activated (basket weave or bw) form. We have examined by electron microscopy and optical diffraction Z lattice forms and dimensions and A band spacings in relaxed, tetanized, stretched, and stretched‐and‐tetanized rat soleus muscle. We have tested the independent contributions of passive load, active tension, and sarcomere length to Z band state. As the A band spacing decreased with increasing load and increasing sarcomere length in the untetanized muscles, the Z lattice remained in the ss form and the Z spacing changed only slightly. Computer‐enhanced images from digitized electron micrographs showed that the ss Z lattice resisted deformation regardless of load or method of stretching. In contrast, when the muscle was tetanized at sarcomere lengths of up to 2.7 μm, the Z lattice assumed the bw form and the Z spacing was increased by 20%. Regardless of lattice form, Z spacing did not vary significantly with sarcomere length. Images from freeze‐substituted preparations showed both lattice forms comparable to those in images from glutaraldehyde‐fixed muscles. Thus, Z band state appears to be a function of the presence (or absence) of active tension. Our previous three‐dimensional model is compatible with these observations and with the substructures revealed by computer‐enhanced images of both lattice forms.—Goldstein, M. A.; Michael, L. H.; Schroeter, J. P.; Sass, R. L. Z band dynamics as a function of sarcomere length and the contractile state of muscle. FASEB J.1: 133‐142; 1987.

The crystal structure of acetylcholine perchlorate has been determined from three-dimensional X-ray diffractometer data. The molecular geometry of this compound differs from that observed for acetylcholine bromide but is structurally similar to that observed for acetylcholine chloride.

1. The bivalve ligament protein has a high percentage of glycine.2. The absence of hydroxyproline and hydroxylysine in the ligament and the lack of a wide angle diffraction pattern indicate that the ligament is not collagen.3. The ligament contains more sulfur amino acids—methionine and cystine/2— than other structural proteins.4. Only the aragonite phase of calcium carbonate has been observed in association with the ligaments.5. Members of the family Pectinidae have the weakest and most resilient ligaments.6. Resilience is inversely correlated with CaCO3and cystine/2 concentration while glycine is directly correlated with resilience.7. The strength factor (opening moment/gram of shell) is distinct from resilience and does not correlate with any of the parameters examined.8. Recovery from compression by inner ligament is probably mediated through easing of steric strains induced during compression.

Summary Electron micrographs and optical diffraction patterns of the Z-band were studied in rat soleus muscle fixed before, during, and after tetanic contraction. We compared the morphology (small square or basketweave pattern) and dimensions of the Z-lattice of control and tetanized muscles near rest length. Z-bands of muscle fixed at rest and of muscle allowed to rest after a tetanic contraction exhibited the small square pattern. Z-bands from muscle fixed during tetanic contraction exhibited the basketweave pattern. Concomitant with the transition to basketweave, we observed an average increase of 20% in spacing between the axial filaments of the Z-lattice. Optical diffraction measurements of the A-bandd10 spacing revealed that the Z/A ratio remained constant during the transition. We have modelled the small square to basketweave transformation as resulting from a change of curvature of constant length cross-connecting Z-filaments when the axial filaments increase their separation.

Structural features of the Z-lattice were examined in cross-sections of rat soleus muscle. Optical diffraction analysis of individual myofilament bundles revealed highly ordered, tightly packed tetragonal lattice regions with abrupt shifts in orientation. Optical reconstructions of cross-sections of the Z-lattice in regions having the same axial filament spacing showed both the basket weave and the small square lattice forms, as well as intermediate structures. Analysis of these regions in three dimensions and in two-dimensional projections suggests that a change in diameter together with a change in curvature of the cross-connecting filaments can explain the different appearances of the Z-lattice at a given sarcomere length.

Irrigated rice cultivation is one of the largest sources (approximately 15–20% of the annual total) of atmospheric methane, a potent greenhouse gas. This review examines the results of work performed over the past six years in which we have investigated the processes leading to the emission of methane from irrigated rice cultivation. These studies describe the daily and seasonal effects on methane production and emission of different planting dates, water management, organic amendments, soil texture, and cultivar choice. Because rice agriculture is one of the few sources of methane where emission reduction through management is considered possible, it promises to be a critical focus of mitigation efforts. We have identified several potential management practices for rice cultivation that may stabilize or reduce the emission of methane even in the face of future increased grain production necessary to meet the demands of an expanding world population.

The crystal structure of 2-diethylaminoethyl-p-nitrobenzoate hydrochloride (C13H18N2O4, HCl) been has determined from three-dimensional diffractometer data. A detailed discussion of the molecular structure is presented, together with a comparison to other similar local anesthetic structures.