Variation Of Decay Rate Research Articles

Further Studies of Root Decomposition Following Harvest of a Northern Hardwoods Forest

Abstract An earlier study of decomposition and nutrient release of root systems following harvest of a northern hardwoods forest ecosystem indicated uncertainties with regard to (1) possible experimental effects on decay of fine and woody roots and (2) patterns of woody root decay and nutrient release in the first several years of decay. Results of this study suggested that most fine roots in the forest floor died early in the first growing season after forest harvest, releasing much of their tissue K. In contrast, mineral soil roots either died much more slowly or were not effectively leached of K during most of the first summer. Rates of release of C and N from fine roots were similar, suggesting that previous studies using mesh bags bad either overestimated N release or underestimated C mineralization, or both. Earlier estimates of total N released from fine roots of northern hardwoods in the first 2 yr after harvest probably were too high. Rates of decay of large woody roots of northern hardwoods were high, with 45%-63% dry weight loss in 4 yr as measured with tethered roots, but this method probably overestimated decay by exposing cut ends to decay organisms. High variation in decay rates was associated especially with the site of incubation, as all the roots (independent of species and size class) incubated in a particular location decayed at about the same rate. For. Sci. 40(4):618-629.

Modeling of Ocean Outfall Discharges

Bacterial modeling techniques for the San Francisco ocean outfall are reviewed. Extensive oceanographic measurements, and field and laboratory experiments were done. The oceanographic data are briefly reviewed and it is shown that all parameters are subject to considerable spatial and temporal variability. A “wandering puff” model is used to compute the frequency distribution of shoreline bacteria. The model accounts for varying initial dilution due to variation in stratification, current speed and direction, and effluent flowrate, far field diffusion due to oceanic turbulence, spatial and temporal variation in current speed and direction, and diurnal variation in bacterial decay rates. It is predicted that bacterial concentration standards will be met at all shoreline locations without effluent chlorination. Areas of uncertainties in our present knowledge of mixing processes are briefly reviewed, and likely future trends discussed.

Decomposition in salt marsh ecosystems of the S.W. Netherlands: the effects of biotic and abiotic factors

Decomposition rates, determined with the litterbag technique in salt marshes of the S.W. Netherlands during the past decade are compared; the biotic and abiotic factors influencing these rates are identified and discussed. Tissue composition is the main variable affecting decay rates of halophytes, particularly variations in lignin content between plant parts and between species. Experiments in which the loss of the tensile strength of cotton strips was used as an index of cellulolytic decay, show that there is a conspicuous variation in decay rates on different sites in a salt marsh. Nonetheless, the locally varying environmental conditions within salt marshes of the S.W. Netherlands have less impact on the variation in decomposition rates of halophyte litter than the chemical make-up of the plant material. Larger fauna elements (> 300 μm) may increase decomposition rates, but this effect is only limited and depends on location and litter type. The role of small fauna elements such as nematodes, which occur abundantly in association with halophyte litter, remains largely unknown.

Variation in Rates of Decay and Disarticulation of Echinodermata: Implications for the Application of Actualistic Data

Actualistic laboratory experiments have documented the preservation potential of selected echinoderms and have calibrated rate of decay with weight-loss of chitin in litter bags. The results are integrated with field experiments which quantified decay rate in flowing seawater, intertidal sediments and freshwater mud using identical litter bags. Decay rate of chitin was generally slower in freshwater sediments than in marine muddy environments and open seawater. Sediment-induced variation in decay rate is within an order of magnitude. The duration of decay required to promote fragmentation varied little between the two regular echinoids but differed by an order of magnitude between the holothurians

The Mössbauer isomer shift calibration problem — Revisited for the Mössbauer isotopes Sn to I

The great deal of work as it is continuously directed towards calibrating the Mossbauer Isomer Shifts of 5s–5p—atoms motivates a critical reconsideration of the corresponding block of data. A greater homogeneity is attained by imposing some methodical improvements particularly on those data which were inferred from measured nuclear decay rate variations. On the basis of these revised data we propose new “best” ΔR/R values for 119Sn,125Te and127,129I: 1.8 10−4, 8.0 10−5, −3.4 10−4 and 4.3 10−4, respectively.

Small scale variation in decay rate within logs one year after felling: Effect of fungal community structure and moisture content

Fungal species composition, moisture content, percentage weight loss, and instantaneous decay rate (expressed by rate of CO2 evolution) was assessed for a total of 186 8 cm3 cubes from 10 beech logs which had been decomposing on the forest floor for 14 months. There was considerable within and between branch variation in decay rate and water content. Water content at the time of sampling was not directly correlated with percentage weight loss or instantaneous decay rate, nor was it correlated with position in the log. However, wood occupied by Ascomycotina (other than Nectria) tended to be drier than that occupied by Basidiomycotina. In particular wood occupied by Xylaria hypoxylon was drier than that occupied by all other species, although wood in which X. hypoxylon was replacing other fungi was wetter than when X. hypoxylon was alone. Variation in percentage weight loss could not be explained in terms of water content and fungal species composition at the time of sampling, but variation in instantaneous decay rate could. Thus, decay rate by Ascomycotina was significantly less (P < 0.05) than by Basidiomycotina, and rate of CO2 evolution from wood occupied by X. hypoxylon alone was significantly slower than from wood in which X. hypoxylon was replacing H. fragiforme or Nectria. The latter was partially correlated with water content but whether this is a cause and effect relationship is uncertain.

Small scale variation in decay rate within logs one year after felling: Effect of fungal community structure and moisture content

Fungal species composition, moisture content, percentage weight loss, and instantaneous decay rate (expressed by rate of CO 2 evolution) was assessed for a total of 186 8 cm 3 cubes from 10 beech logs which had been decomposing on the forest floor for 14 months. There was considerable within and between branch variation in decay rate and water content. Water content at the time of sampling was not directly correlated with percentage weight loss or instantaneous decay rate, nor was it correlated with position in the log. However, wood occupied by Ascomycotina (other than Nectria) tended to be drier than that occupied by Basidiomycotina. In particular wood occupied by Xylaria hypoxylon was drier than that occupied by all other species, although wood in which X. hypoxylon was replacing other fungi was wetter than when X. hypoxylon was alone. Variation in percentage weight loss could not be explained in terms of water content and fungal species composition at the time of sampling, but variation in instantaneous decay rate could. Thus, decay rate by Ascomycotina was significantly less ( P < 0.05) than by Basidiomycotina, and rate of CO 2 evolution from wood occupied by X. hypoxylon alone was significantly slower than from wood in which X. hypoxylon was replacing H. fragiforme or Nectria. The latter was partially correlated with water content but whether this is a cause and effect relationship is uncertain.

Persistent current in Ba-Y-Cu-O in liquid nitrogen.

A persistent-current experiment maintained for 12 days with a sample of Ba/sub 0.4/Y/sub 0.6/CuO/sub 3-//sub y/ is reported. The estimated upper limit of resistivity is 2 x 10/sup -18/ ohm cm. A logarithmic decay at the beginning is detected, which is in good agreement with the flux-creep theory. Variations in decay rate due to changes of trapped field and temperature are measured.

Precise Radiometry: Some Recent Aspects of Fruitful Interaction with Atomic Physics

Modern radiometric analytics demands a complex consideration of nuclear and electron shell processes, if more pretentious aims are envisaged. As an example the small variation of decay rates of radionuclides presents possibilities for information on chemical situations of decaying atoms. In principle this phenomenon is well known since many years, but now the situation is such that, e.g. in 99mTc internal conversion, a full agreement of the difficult experiments and the respective theory was established. The secondary emission of X-rays as a consequence of high excitation of electron shells in combination with nuclear transitions supplies another example for a methodical progress of radiometry. Investigations on 51Cr as an electron capture nuclide have shown that chemically induced variations of the Kα to Kβ X-ray intensity ratio is at least qualitatively understood.

Factors Controlling the Survival of Viruses in Groundwater

The purpose of this work was to define factors which control virus survival in groundwater. Groundwater samples collected from throughout the United States were inoculated with the coliphage MS-2 and the rate of virus inactivation determined. All samples were incubated at the temperature of the native groundwater. All samples were analyzed for pH, nitrates, ammonia, turbidity, total dissolved solids, and calcium, magnesium and total hardness. Multiple regression analysis of the chemical variates indicated that temperature and calcium hardness were significantly correlated with the rate of virus die-off. Temperature alone account for 60% of the variation in decay rate. Using all variates, 94% of the variation could be predicted.

Wood decomposition in an abandoned beech and oak coppiced woodland in SE England

The rate of litter decomposition is often expressed as a constant decay rate (k; g g−1 yr−1) or as the time required for a certain percentage (often 95% and estimated as 3/k) of it to decompose (termed turnover time). Estimates of k may be obtained by determining the weight loss of litter in the field and also by assuming a steady state and obtaining the ratio of litter input: standing crop. Both methods were used to estimate decay rate and turnover times for beech and oak branches and twigs decomposing on the forest floor and these were critically evaluated.Considerable variation, ranging between 1.8–144.5 yr, was found between the 95% turnover time estimates of various size components of the two species, obtained from woodfall and standing crop data. Likewise variation in decay rate of 2–2.5 cm diameter beech branches, estimated from field experiments, was large both between and within groups of branches categorised according to initial state of decay and presence or absence of bark. The mean annual decay rate for the various categories ranged between k = 0.165‐0.452 g g−1yr−1. Branches without bark generally decomposed more slowly than those with bark. Beech twig (&lt;0.5 cm diameter) decomposition rates, from field experiments, ranged between k = 0.149‐0.220 g g−1yr−1 and variation was relatively low compared with that of branches. No significant differences (P&lt;0.05)were detected between twig decomposition rates obtained from experiments initiated at different seasons although there was a slight decline in decay rate in winter months. Twig and branch decomposition rates fell within the range found in the few other comparable studies.

Autumn Leaf Fall and Nutrient Return in an Old-Growth and a Second-Growth Forest in Eastern Kentucky

Autumn leaf fall was sampled in two watersheds, one containing an old-growth stand and the other a 35-yr-old second-growth stand of mixed mesophytic forest in eastern Kentucky Total leaf fall and its composition did not differ between the two watersheds and averaged 291 g/m2 Weighted average nutrient concentrations exhibited spatial variation, which paralleled a previously established soil fertility gradient Total nutrient return by autumn leaf fall was greatest on mid-slope sites of both watersheds, where soil pH and nutrient availability are greatest The combination of bulk nutrient return by leaf fall and of recognized variation in leaf decay rates suggests that the soil fertility gradient within each stand may be tied to internal nutrient cycling characteristics of the vegetation

Some practical aspects of absorption measurements in reverberation rooms

This paper discusses the results of a series of computer controlled measurements of sound absorption coefficients in a single reverberation room. The effects of factors such as diffuser area, microphone position, and rotating diffusers on the measurements are discussed. Spatial variations of decay rate, curvature, and measured absorption coefficients determine the precision of the measurements. The practical procedures necessary to achieve satisfactory precision are compared with those allowed in standard test methods.

Variation in radical decay rates in epoxy as a function of crosslink density

Journal of Applied Polymer ScienceVolume 28, Issue 10 p. 3301-3307 NoteFree Access Variation in radical decay rates in epoxy as a function of crosslink density G. M. Kent, G. M. Kent North Carolina State University, Raleigh, North Carolina 27607Search for more papers by this authorJ. M. Memory, J. M. Memory North Carolina State University, Raleigh, North Carolina 27607Search for more papers by this authorR. D. Gilbert, R. D. Gilbert North Carolina State University, Raleigh, North Carolina 27607Search for more papers by this authorR. E. Fornes, R. E. Fornes North Carolina State University, Raleigh, North Carolina 27607Search for more papers by this author G. M. Kent, G. M. Kent North Carolina State University, Raleigh, North Carolina 27607Search for more papers by this authorJ. M. Memory, J. M. Memory North Carolina State University, Raleigh, North Carolina 27607Search for more papers by this authorR. D. Gilbert, R. D. Gilbert North Carolina State University, Raleigh, North Carolina 27607Search for more papers by this authorR. E. Fornes, R. E. Fornes North Carolina State University, Raleigh, North Carolina 27607Search for more papers by this author First published: October 1983 https://doi.org/10.1002/app.1983.070281024Citations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat References 1 K. Schaffer, “Characterization of a Cured Epoxy Resin Exposed to High Energy Radiation with Electron Spin Resonance,” M. S. thesis, North Carolina State University, 1981. 2 K. Schaffer, R. D. Gilbert, J. D. Memory, and R. E. Fornes, Bull. Am. Phys. Soc., 26, 432 (1981). 3 K. Schaffer, R. E. Fornes, R. D. Gilbert and J. D. Memory, Polymer, to appear. 4 I. M. Brown, A. C. Lind, and T. C. Sandreczki, Department of the Navy Contract Report MDC 00721, 1980. 5 I. M. Brown, A. C. Lind, and T. C. Sandreczki, Department of the Navy Contract Report MDC 00673, 1979. 6 Ursula T. Kreibich and Rolf Schmid, J. Polym. Sci., Symp. 53, 177 (1975). 7 Roger J. Morgan and James E. O'Neal, J. Maters. Sci., 12, 1966 (1977). 8 R. J. Morgan and J. E. O'Neal, Am. Chem. Soc., Div. Org. Coatings Plast. Chem., 38, 485 (1977). 9 Jovan Mijovic and J. A. Koutsky, Polymer, 20, 1095 (1979). 10 R. J. Morgan, Am. Chem. Soc., Div. Org. Coatings Plast. Chem., 40, 678 (1980). 11 S. J. Wyard, J. Sci. Instrum., 2, 769 (1965). 12 M. Dole, C. Hso, V. M. Patel, and G. N. Patel, J. Phys. Chem., 19, 2473 (1975). 13 James P. Bell, J. Appl. Polym. Sci., 27, 3503 (1982). Citing Literature Volume28, Issue10October 1983Pages 3301-3307 ReferencesRelatedInformation

Autocorrelation of Northern Hemisphere Geopotential Heights

Local autocorrelation statistics for the Northern Hemisphere geopotential height field are presented for different seasons and tropospheric pressure levels. Values are generally much higher than those calculated from time series of outgoing infrared radiation or eddy heat fluxes. The largest one-day lag autocorrelation values are observed over the polar regions and eastern oceans. Well-defined minima exist off the cast coasts of Asia and North America. The minima are most distinct in winter, and are shifted northward and weaker during summer. Otherwise, the pattern does not change drastically with season. These geographical patterns do not change much with height, but the minima are less sharply defined at upper tropospheric levels. At longer lags, the extratropical maxima remain distinct, but the minima shift westward over the continents and cover a broader area, as the autocorrelation approaches zero with increasing lag. Values remain high over the tropics, where height anomalies tend to persist for many days. A comparison of observed autocorrelations with red noise decay suggests that geographical variations in decay rates are associated with the relative importance of baroclinic and barotropic components to the total height variability and with advective effects on the local statistics.

Direct Chemical Information from Special Radiotracers as well as from Outer X-Ray Excitation

Radionuclides which exhibit a larger interaction between nucleus and electron shell during their radioactive decay (especially electron capture and internal conversion) are, in principle, sensitive to their chemical surroundings. Consequently they can be used to yield chemical information after an appropriate labelling procedure. The information can be extracted from the decay rate variation as well as from their X-ray emission as a response to an inner-shell vacancy creation during nuclear deexcitation. As an example of the former method the relationship between the decay rate of 99mTc and the chemical structures of pertechnetate and bis(meso-dimercapto-succinato)oxotechnetate (V) is considered. Lower expectations with respect to measuring techniques are associated with the observation of X-ray emission. For a number of elements (especially in the 3d transition row) the Kα/Kβ X-ray intensity ratio was found to be an indicator of the nearest neighbour atoms. Equivalent information can be drawn from outer X-ray excitation, too.

Compositional dependence of nonradiative decay rate in Nd laser glasses

Variations of nonradiative decay rate from 4 F 3 2 of a neodymium ion with the change of network modifier were determined from the fluorescence lifetime and radiative decay rate, calculated on the basis of Judd-Ofelt theory, for silicate and phosphate glasses. While, on the basis of Miyakawa-Dexter's theory, the nonradiative decay rate due to the multiphonon relaxation process was estimated from the electron-phonon coupling strength and phonon energy which were in turn determined from phonon sideband measurements. The latter did not always give the same modifier dependence of the nonradiative decay rate as the former, which suggested that the Judd-Ofelt theory did not always give the precise value of the radiative decay rate. The opposite variations of nonradiative decay rate with alkali modifier were found for silicate and phosphate glasses. This was explained as a result of the difference in the contribution of the electron-phonon coupling strength to the nonradiative decay rate due to the multiphonon relaxation process.

Oscillatory electrographic activity in the hippocampus: A mathematical model

This model of hippocampal function describes the bilaterally symmetrical interactions of the various intrahippocampal populations of neurons that are functionally homogeneous (septal and entorhinal sources of input, granule cells, CA field pyramidal cells, and basket cells). Activity of each homogeneous population is described as a first order nonlinear differential equation. Parameters are simulated, with activity defined in relative units ranging from 0 to 1.0. The 26 equations (13 identified pools in each hemisphere) were solved simultaneously by computer to produce plots of the time course of activity changes in each of the populations. The simulations performed thus far show that the model parallels certain known properties of the system: (1) there is the expected reciprocal relationship between pyramidal cells and basket cells; (2) activity can be made to oscillate or achieve steady-state, simulating EEG “theta” rhythm or low voltage, fast activity; (3) oscillation occurs where it is known to occur (CA 1 pyramidal cells and the dentate region), where it is presumed to occur (in basket cells), and does not occur where it is known not to occur (CA 2 pyramidal cells); (4) there is a narrow range of frequency, and attempts to increase frequency readily terminate oscillation to cause steady-state activity: (5) oscillation requires excitatory drive from the medial septum, whereas entorhinal input is relatively less important: and (6) increases in medial septal activity can increase oscillation frequency. The results also predict certain undiscovered phenomena: (1) there is a major influence of variations in decay rate of activity in various neuronal pools; (2) there is probably an ultra-slow oscillation in the CA 2 area; and (3) the CA 1 projection to the entorhinal cortex seems to be important in modulating frequency and amplitude of theta rhythm.

Advances in architectural acoustics.

Four areas of research in architectural acoustics in which significant advances have been achieved recently are discussed. 1. Reliable determination of subjective preference of concert hall acoustics by means of faithful (three-dimensional) reproduction of music recorded in concert halls with an acoustically realistic dummy head: The main new result, based both on real halls and digital simulations of halls, is that interaural dissimilarity should be high for high preference. This finding implies the need for more lateral diffusion in concert halls. 2. Effective methods for increasing sound diffusion: In modern wide halls with low ceilings, the two ear signals for a listener on the main floor tend to be very similar owing to strong ceiling reflections (relative to the reflections from the side walls). Thus, ceiling structures for scattering sound laterally should improve concert hall quality. Such structures, based on two number-theoretic principles (quadratic residues and primitive roots) are discussed. 3. Proper calculation of reverberation time: Sound decay rates and sound energy fluxes, based on ray theory, are given by two integral equations. Their solution, recently achieved, shows variations of decay rates by as much as 48% depending only on absorber location!(The Sabine and Eyring formulas, of course, predict no such variations and consequently lead to costly errors.) 4. Making meaningful measurements in acoustic enclosures: A recently discovered fast inverse for measurements using maximum-length pseudo-random noise is described. Some implications for making measurements with music during ongoing performance, are discussed.

Intersarcomere dynamics during fixed‐end tetanic contractions of frog muscle fibres.

1. The stability of sarcomere lengths along single twitch fibres from frog muscles was examined during fixed-end tetani, using a spot follower apparatus to monitor the length of a central segment. 2. Internal movement, with most of the fibre lengthening and small regions at the ends shortening as the contraction proceeded, was always seen at fibre lengths beyond those corresponding to a sarcomere length of 2.3 micrometer. 3. The rate of lengthening of the central region was fastest during the slow phase of tension rise (creep) but continued at a slower rate throughout the tetanus. These observations are in accord with the idea that progressive development of sarcomere non-uniformity is responsible for the creep phase. 4. Observations at various muscle lengths of the rate of decay of tension and the duration of the slow phase of relaxation suggest that movement during relaxation is due to sarcomere length non-uniformities and variations of decay rate with sarcomere length. 5. The rate of tension fall after stimulation ceases in an isometric sarcomere, and the factors which determine that rate, are discussed in view of evidence from fixed-end and length-clamped tetani, and recently reported experiments using aequorin.