High precision U-Pb zircon ages for Mesozoic igneous rocks from Hong Kong

Sixteen new high precision U–Pb zircon ages are reported from Jurassic and Early Cretaceous silicic volcanic and plutonic rocks of HongKong. When combined with the existing age dataset, the new ages constrain more tightly the timing of major periods of volcanism and plutonism at 162.6 ± 4.5 Ma, 146.7 ± 1.1 Ma, 143.0 ± 1.0 Ma and 140.8 ± 0.6 Ma. However, two ages of 151.9 ± 0.2 Ma and 148.1 ± 0.2 Ma, from eastern New Territories and southern HongKong indicate additional and therefore more continuous, albeit pulsed, magmatic activity than previously thought

Effect of cereal rotations on soil pH, organic matter, and microbial properties of a Brown loam

Non-Peer Reviewe

Agrispon™ fails to prove claims in scientific testing

Non-Peer Reviewe

Marine Platform of Probable Sangamon Age, and Associated Terrace Deposits, Cape Thompson Area, Northwestern Alaska

Reports geomorphic studies, as part of the US Atomic Energy Commission's investigations in this area 1958-1962. A coastal terrace, observed and measured along a 20-mi section crossing Ogotoruk Creek, is described and its origin, age, and morphology discussed. The feature is complex, consisting of a marine platform planed across bedrock, overlying marine and beach deposits, and a depositional upper surface of nonmarine sediments which coincides in area and configuration with the platform, possibly as a result of factors unique to polar areas. The marine platform and gravels record the last high stand of sea level, 28-40 ft above the present, which occurred about 38,000 yr ago. Other evidence in the area indicates still higher seas in earlier times

The effect of organic structures on the water stability of macro-aggregates.

Non-Peer ReviewedA study was conducted to identify the chemical structures of soil organic matter and examine their effect on the water stability of macro-aggregates (>250 um) in a SiL Brown Chernozem under wheat-fallow (WF) and continuous wheat (CW) . The proportion of water stable macro-aggregates were determined by wet sieving. Chemical structures of soil organic matter were characterized by pyrolysis field ionization mass spectrometry (Py-FIMS), and grouped into seven classes: carbohydrates, phenolic and lignin monomers, lignin dimers, lipids + alkanes and alkenes, sterols, alkyl aromatic and N-compounds. In comparison with CW, there was a reduction in the proportion of macro-aggregates and an increase of micro-aggregates in the WF crop rotation. Sixty-five percent of all the soil organic matter (SOM) was identified by Py-FIMS. The average concentration of each class of compound in whole soil and macro-aggregate samples ranged between 0.1 and 15% of the total identified SOM. Carbohydrates, phenolic, and lignin monomers were the most abundant compounds (>10%). Linear regression models (r2 ~ 0.96, p=0.05) showed that the stability of macro-aggregates was highly correlated with the concentration of the least abundant (<3. 5%) structures of sterols, lipids and lignin dimers. These compounds are metabolic products of plants and soil organisms

Effect of stubble height and source, rate, time, and method of application of N on yield of spring and winter wheat grown under zero-till

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Simulating the dynamics of soil organic matter in long-term rotation plots of Saskatchewan and Alberta

Non-Peer ReviewedThis study used the Century soil organic matter (SOM) model to simulate the dynamics in soil organic carbon, nitrogen, and phosphorus in long-term crop rotation studies established in Saskatchewan and Alberta. Observed losses of organic C, N, and P in the top 30 cm of a Brown Chernozem under fallow-wheat (FW) were 8.2, 1.7, and 1.0 g m-1 y-1. Soil erosion was responsible for 47% of the organic-N losses. The Century model closely mimicked the direction and magnitude of SOM change, within 10% of measured values. Similar SOM declining trends were observed in a thin Black Chernozem under FW and continuous wheat (CW), although soil erosion losses were higher than in the Brown Chernozem. Soil organic matter increased in the Brown Chernozem under CW and in the Black Chernozem under zero-tillage. Under no-till, the organic C, N, and P accumulated at an average rate of 101.7, 5.3, and 2.0 g m-2 y-1. In comparison, the Century model predicted a depletion of organic-C and N in the Brown Chernozem under CW and of organic-C under no-till. Model sensitivity analyses indicated that the rate of erosion and the fixed rate of organic matter decomposition had greater effects than plant biomass production on soil organic matter levels. Under aggrading SOM conditions, the Century model predicted organic carbon accumulation only after the respiration rate for the slow organic matter fraction was reduced by 50%

Kinks in the Presence of Rapidly Varying Perturbations

Dynamics of sine-Gordon kinks in the presence of rapidly varying periodic perturbations of different physical origins is described analytically and numerically. The analytical approach is based on asymptotic expansions, and it allows to derive, in a rigorous way, an effective nonlinear equation for the slowly varying field component in any order of the asymptotic procedure as expansions in the small parameter $\omega^{-1}$, $\omega$ being the frequency of the rapidly varying ac driving force. Three physically important examples of such a dynamics, {\em i.e.}, kinks driven by a direct or parametric ac force, and kinks on rotating and oscillating background, are analysed in detail. It is shown that in the main order of the asymptotic procedure the effective equation for the slowly varying field component is {\em a renormalized sine-Gordon equation} in the case of the direct driving force or rotating (but phase-locked to an external ac force) background, and it is {\em the double sine-Gordon equation} for the parametric driving force. The properties of the kinks described by the renormalized nonlinear equations are analysed, and it is demonstrated analytically and numerically which kinds of physical phenomena may be expected in dealing with the renormalized, rather than the unrenormalized, nonlinear dynamics. In particular, we predict several qualitatively new effects which include, {\em e.g.}, the perturbation-inducedComment: New copy of the paper of the above title to replace the previous one, lost in the midst of the bulletin board. RevTeX 3.