bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbulence measurements in marine stratocumulus with airborne Doppler radar
Authors: Lothon M. , Lenschow D. H. , Leon D. , Vali G.
Published: July 2005

This study investigates the ability of a W‐band radar to measure turbulence structure as a function of height throughout the drizzling marine boundary layer from the fine‐structure of the Doppler velocity field obtained during Dynamics and Chemistry of Marine Stratocumulus Experiment using the NCAR C‐130 aircraft. In situ air velocity measurements are used as a basis for the comparison with radar measurements of turbulence energy and dissipation, and integral length‐scale, after correcting for the effects of velocity averaging within the pulse resolution volume and random uncorrelated noise. One essential step for this study is to estimate the contribution to the fluctuations in Doppler velocity due to the terminal velocity of hydrometeors. To do this, we use microphysics probe measurements of the spatial distribution of the drop counts in each size bin. We find a small velocity standard deviation (0.05 to 0.1 m s−1) contributed by the radar‐measured drizzle fall velocity and a substantial negative correlation between air vertical velocity and this fall velocity in the upper part of the cloud. This correlation has an impact on the turbulent energy and dissipation deduced from the Doppler velocity. However, it does not significantly affect the integral scales, which are in good agreement with the in situ measurements. Thus, the radar enables us to obtain the profile of this key variable through the entire cloud‐capped boundary layer. We obtain estimates of the dissipation in the lower 2/3 of the boundary layer that are in excellent agreement with the in situ measurements and consistent with the predominant production terms in the turbulent kinetic energy budget. Copyright © 2005 Royal Meteorological Society.
A comparison of variance and total‐energy singular‐vectors
Authors: Reynolds C. A. , Gelaro R. , Rosmond T. E.
Published: July 2005

The analysis‐error variance estimates produced by the Naval Research Laboratory Atmospheric Variational Data Assimilation System are used to constrain singular vectors (SVs) at initial time (the final‐time metric is total energy). These ‘VAR SVs’ are compared to SVs for which total energy is both the initial‐ and final‐time metrics (TE SVs). The spatial distributions and structures of the VAR SVs and TE SVs are examined and their effectiveness in explaining forecast error is compared. Consistent with previous results, the VAR SVs have relatively larger amplitude than TE SVs in regions where analysis errors are larger (such as over oceans and polar regions). In contrast to previous results, the initial‐time VAR SV energy peaks at lower altitudes than the TE SV energy, reflecting the influence of the data‐assimilation‐error variance estimates. Despite these significant differences, the TE and VAR SVs explain comparable amounts of forecast error in both linear and nonlinear contexts. By projecting the VAR SV pseudo‐inverse perturbation onto the TE SVs, it is found that the component inside the TE‐SV subspace accounts for most of the forecast‐error reduction. The component outside the TE‐SV subspace has very little impact on error reduction. It is noteworthy that for both the TE and VAR SVs, nonlinear pseudo‐inverse forecast‐corrections are better than the expected linear corrections. Both sets of SVs exhibit a relationship between singular‐vector growth and forecast‐error total energy, when averaged over many cases. This indicates that the SVs have some utility in predicting forecast‐error variance. Copyright © 2005 Royal Meteorological Society.
Parametrization of ice‐particle size distributions for mid‐latitude stratiform cloud
Authors: Field P. R. , Hogan R. J. , Brown P. R. A. , Illingworth A. J. , Choularton T. W. , Cotton R. J.
Published: July 2005

Particle size distributions measured by the UK C‐130 aircraft in ice stratiform cloud around the British Isles are analysed. Probability distribution functions over large scales show that the zeroth, second and fourth moments (equivalent to concentration, ice water content and radar reflectivity) as well as mean particle size have monomodal distributions. Rescaling of the size distributions requiring knowledge of two moments reveals a ‘universal’ distribution that has been fitted with analytically integrable functions. The existence of the ‘universal’ distribution implies that two‐moment microphysics schemes are adequate to represent particle size distributions (PSDs). In large‐scale models it may be difficult to predict two moments, and so power laws between moments have been found as functions of in‐cloud temperature. This means that a model capable of predicting ice water content and temperature can predict ice PSDs to use for calculations requiring knowledge of the size distribution (e.g. precipitation rate, radar reflectivity) or to make direct use of the power laws relating moments of the size distribution. © Royal Meteorological Society, 2005. Contributions by P. R. Field, P. R. A. Brown and R. J. Cotton are Crown copyright.
Resistance and heat‐transfer laws for stable and neutral planetary boundary layers: Old theory advanced and re‐evaluated
Authors: Zilitinkevich Sergej S. , Esau Igor N.
Published: July 2005

The planetary boundary layer (PBL) resistance and heat‐transfer laws express the surface fluxes of momentum and heat through the PBL governing parameters. Since the late sixties, the dimensionless coefficients (A, B and C) in these laws were considered as single‐valued functions of internal stability parameters: µ=u*/|f|Ls in the steady state PBLs, or h/Ls in the evolving PBLs (u* is the friction velocity, f is the Coriolis parameter, Ls is the surface Monin–Obukhov length, and h is the PBL depth). Numerous studies revealed very wide spread of data in empirical plots of A, B and C versus µ or h/Ls. It is not surprising that the above laws, although included in all modern textbooks on boundary‐layer meteorology, are not practically used. In the present paper the resistance and heat‐transfer laws are revised, accounting for the free‐flow stability, baroclinicity and the rise of a capping inversion. The coefficients A, B and C become functions not only of µ or h/Ls, but also of the external stability parameter µN=N/|f| (where N is the Brunt–Väisälä frequency in the free atmosphere above the PBL), the parameter of baroclinicity µΓ=Γ/N (or the free‐flow Richardson number Ri=(N/Γ)2=µΓ−2, where Γ is the geostrophic wind shear), and the ratio of the actual and equilibrium PBL depths h/hE. Moreover, the coefficient C is redefined to account for the effect of a capping inversion. It follows that A, B and C can be considered as single‐valued functions of µ only in the steady‐state, barotropic, nocturnal (that is short‐lived) PBL. On the other hand, the advanced laws cover a wide range of the PBL regimes. They are validated through large‐eddy simulations of different types of PBLs: truly neutral, conventionally neutral, nocturnal and long‐lived. This new development explains why prior formulations performed so poorly, and promotes advanced resistance and heat‐transfer laws as practical tools for use in environmental modelling applications. Copyright © 2005 Royal Meteorological Society.
Resonant gravity‐wave drag enhancement in linear stratified flow over mountains
Authors: Teixeira M. A. C. , Miranda P. M. A. , Argain J. L. , Valente M. A.
Published: July 2005

High‐drag states produced in stratified flow over a 2D ridge and an axisymmetric mountain are investigated using a linear, hydrostatic, analytical model. A wind profile is assumed where the background velocity is constant up to a height z1 and then decreases linearly, and the internal gravity‐wave solutions are calculated exactly. In flow over a 2D ridge, the normalized surface drag is given by a closed‐form analytical expression, while in flow over an axisymmetric mountain it is given by an expression involving a simple 1D integral. The drag is found to depend on two dimensionless parameters: a dimensionless height formed with z1, and the Richardson number, Ri, in the shear layer. The drag oscillates as z1 increases, with a period of half the hydrostatic vertical wavelength of the gravity waves. The amplitude of this modulation increases as Ri decreases. This behaviour is due to wave reflection at z1. Drag maxima correspond to constructive interference of the upward‐ and downward‐propagating waves in the region z<z1, while drag minima correspond to destructive interference. The reflection coefficient at the interface z=z1 increases as Ri decreases. The critical level, zc, plays no role in the drag amplification. A preliminary numerical treatment of nonlinear effects is presented, where zc appears to become more relevant, and flow over a 2D ridge qualitatively changes its character. But these effects, and their connection with linear theory, still need to be better understood. Copyright © 2005 Royal Meteorological Society.
Linear criteria for gravity‐wave breaking in resonant stratified flow over a ridge
Authors: Teixeira M. A. C. , Miranda P. M. A.
Published: July 2005

Using linear theory, it is shown that, in resonant flow over a 2D mountain ridge, such as exists when a layer of uniform wind is topped by an environmental critical level, the conditions for internal gravity‐wave breaking are different from those determined in previous studies for non‐resonant flows. For Richardson numbers in the shear layer not exceeding 2.25, two zones of flow overturning exist, respectively below and downstream and above and upstream of the expected locations. Flow overturning occurs for values of the dimensionless height of the ridge smaller than those required for a uniform wind profile. These results may have implications for the physical understanding of high‐drag states. Copyright © 2005 Royal Meteorological Society.
Extension of an orographic‐drag parametrization scheme to incorporate orographic anisotropy and flow blocking
Authors: Kim Young‐joon , Doyle James D.
Published: July 2005

The Kim–Arakawa orographic gravity‐wave drag parametrization scheme, which is a component of the US Navy's NOGAPS ALPHA (Navy Operational Global Atmospheric Prediction System, Advanced‐Level Physics and High Altitude), is extended to include the effects of orographic anisotropy and low‐level flow blocking. The algorithms to calculate the orographic statistics needed for the parametrization are also revised. The extended scheme is evaluated against mountain waves explicitly simulated with COAMPS®† (Coupled Ocean/Atmosphere Mesoscale Prediction System) of NRL (Naval Research Laboratory).

Mountain‐wave simulations over Boulder, Colorado, USA, are used for representing realistic situations of different wave activity including severe downslope windstorms. The simulations are area‐averaged and interpolated to the vertical grid of NOGAPS, and are used as the input to the extended Kim–Arakawa scheme. The scheme is calibrated by comparing the parametrized vertical distribution of the momentum fluxes with the counterpart obtained from the explicit mesoscale simulations. Overall, the calibrated scheme successfully represents the simulated magnitudes and vertical divergences of the momentum fluxes. A flow regime diagram is constructed utilizing a time series of the simulations to further evaluate the parametrization. The robustness of the orographic statistics, together with an approximate method to improve it, are also addressed. Copyright © 2005 Royal Meteorological Society.
Investigation of the sensitivity of the ECMWF radiation scheme to input parameters using the adjoint technique
Authors: Janiskov'a Marta , Morcrette Jean‐jacques
Published: July 2005

The potential of the adjoint technique for studying the sensitivity of a physical parametrization scheme to its input parameters is investigated. Compared with the standard evaluation approach, where the sensitivity of all the outputs is obtained by modifying one given input, the adjoint method offers a complementary and very efficient approach for sensitivity studies. The paper focuses on an estimation of the sensitivity of the ECMWF radiation schemes to changes in temperature, humidity, aerosols and cloud properties. The sensitivity of the topof‐atmosphere radiation fluxes in clear‐ and cloudy‐sky conditions, computed globally by the ECMWF model for the different seasons, is discussed in this study. This allows us to investigate spatial and temporal patterns in the sensitivity variations. The evaluation of the Jacobian of radiation fluxes by the adjoint technique provides an insight on the extent to which the various radiation fluxes are sensitive to the meteorological variables and confirms results usually obtained by more computationally intensive traditional methods. In addition, such a sensitivity study gives some indications on the importance and efficiency of particular types of observations in modifying the initial conditions of a model. Copyright © 2005 Royal Meteorological Society.
The impact of the stratosphere on the troposphere during the southern hemisphere stratospheric sudden warming, September 2002
Authors: Charlton A. J. , O'neill A. , Lahoz W. A. , Massacand A. C. , Berrisford P.
Published: July 2005

Recent research has established that a small but statistically significant link exists between the stratosphere and the troposphere in the northern hemisphere extratropics. In this paper it is shown that a similar link exists between the stratosphere and troposphere during the unprecedented September 2002 sudden warming in the southern hemisphere. Two ensemble forecasts of the stratospheric sudden warming are run which have different stratospheric initial conditions and identical tropospheric initial conditions. Stratospheric initial conditions have an impact on the tropospheric flow at the peak of the major warming (5 days into the run) and on longer time‐scales (18 days into the run). The character of this influence is a localized, equatorward shift of the tropospheric storm track. The averaged impact of the change in the position of the storm‐track maps strongly onto the Southern Annular Mode structure, but does not have an annular character. Copyright © 2005 Royal Meteorological Society.
Consistent approximate models of the global atmosphere: shallow, deep, hydrostatic, quasi‐hydrostatic and non‐hydrostatic
Authors: White A. A. , Hoskins B. J. , Roulstone I. , Staniforth A.
Published: July 2005

We study global atmosphere models that are at least as accurate as the hydrostatic primitive equations (HPEs), reviewing known results and reporting some new ones. The HPEs make spherical geopotential and shallow atmosphere approximations in addition to the hydrostatic approximation. As is well known, a consistent application of the shallow atmosphere approximation requires omission of those Coriolis terms that vary as the cosine of latitude and of certain other terms in the components of the momentum equation. An approximate model is here regarded as consistent if it formally preserves conservation principles for axial angular momentum, energy and potential vorticity, and (following R. Müller) if its momentum component equations have Lagrange's form. Within these criteria, four consistent approximate global models, including the HPEs themselves, are identified in a height‐coordinate framework. The four models, each of which includes the spherical geopotential approximation, correspond to whether the shallow atmosphere and hydrostatic (or quasi‐hydrostatic) approximations are individually made or not made. Restrictions on representing the spatial variation of apparent gravity occur. Solution methods and the situation in a pressure‐coordinate framework are discussed. © Crown copyright 2005.
Spatial distribution of cloud droplets in a turbulent cloud‐chamber flow
Authors: Jaczewski A. , Malinowski S. P.
Published: July 2005

We present the results of a laboratory study of the spatial distribution of cloud droplets in a turbulent environment. An artificial, weakly turbulent cloud, consisting of droplets of diameter around 14µm, is observed in a laboratory chamber. Droplets on a vertical cross‐section through the cloud interior are imaged using laser sheet photography. Images are digitized and numerically processed in order to retrieve droplet positions in a vertical plane. The spatial distribution of droplets in the range of scales, l, from 4 to 80 mm is characterized by: the clustering index CI(l), the volume averaged pair correlation function η(l) and a local density defined on a basis of correlation analysis. The results indicate that, even in weak turbulence in the chamber that is less intense and less intermittent than turbulence observed in clouds, droplets are not spread according to the Poisson distribution. The importance of this deviation from the Poisson distribution is unclear when looking at CI(l) and η(l). The local density indicates that in small scales each droplet has, on average, more neighbours than expected from the average droplet concentration and gives a qualitative and intuitive measure of clustering. Copyright © 2005 Royal Meteorological Society.
Evaluation of probabilistic prediction systems for a scalar variable
Authors: Candille G. , Talagrand O.
Published: July 2005

A systematic study is performed of a number of scores that can be used for objective validation of probabilistic prediction of scalar variables: Rank Histograms, Discrete and Continuous Ranked Probability Scores (DRPS and CRPS, respectively). The reliability‐resolution‐uncertainty decomposition, defined by Murphy for the DRPS, and extended here to the CRPS, is studied in detail. The decomposition is applied to the results of the Ensemble Prediction Systems of the European Centre for Medium‐range Weather Forecasts and the National Centers for Environmental Prediction. Comparison is made with the decomposition of the CRPS defined by Hersbach. The possibility of determining an accurate reliability‐resolution decomposition of the RPSs is severely limited by the unavoidably (relatively) small number of available realizations of the prediction system. The Hersbach decomposition may be an appropriate compromise between the competing needs for accuracy and practical computability. Copyright © 2005 Royal Meteorological Society.
On the use of the super compact scheme for spatial differencing in numerical models of the atmosphere
Authors: Esfahanian V. , Ghader S. , Mohebalhojeh A. R.
Published: July 2005

The ‘Super Compact Finite‐Difference Method’ (SCFDM) is applied to spatial differencing of some prototype linear and nonlinear geophysical fluid dynamics problems. An alternative form of the SCFDM relations for spatial derivatives is derived. The sixth‐order SCFDM is compared in detail with the conventional fourth‐order compact and the second‐order centred differencing. For the frequency of linear inertia‐gravity waves on different numerical grids (Arakawa's A–E and Randall's Z) related to the Rossby adjustment process, the sixth‐order SCFDM shows a substantial improvement on the conventional methods. For the Jacobians involved in vorticity advection by non‐divergent flow and in the Bolin–Charney balance equation, a general framework, valid for every finite‐difference method, is derived to present the discrete forms of the Jacobians. It is found that the sixth‐order SCFDM provides a noticeably more accurate representation of the wave‐number distribution of the Jacobians, when compared with the conventional methods. The problem of reconstructing the stream‐function field from the vorticity field on a sphere is also considered. For the Rossby–Haurwitz wave, the computation of a normalized global error at different horizontal resolutions in longitude and latitude directions shows that the sixth‐order SCFDM can markedly improve on the fourth‐order compact. The sixth‐order SCFDM is thus proposed as a viable method to improve the accuracy of finite‐difference models of the atmosphere. Copyright © 2005 Royal Meteorological Society.
Anvil glaciation in a deep cumulus updraught over Florida simulated with the Explicit Microphysics Model. I: Impact of various nucleation processes
Authors: Phillips Vaughan T. J. , Andronache Constantin , Sherwood Steven C. , Bansemer Aaron , Conant William C. , Demott Paul J. , Flagan Richard C. , Heymsfield Andy , Jonsson Haflidi , Poellot Micheal , Rissman Tracey A. , Seinfeld John H. , Vanreken Tim , Varutbangkul Varuntida , Wilson James C.
Published: July 2005

Simulations of a cumulonimbus cloud observed in the Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment (CRYSTAL‐FACE) with an advanced version of the Explicit Microphysics Model (EMM) are presented. The EMM has size‐resolved aerosols and predicts the time evolution of sizes, bulk densities and axial ratios of ice particles. Observations by multiple aircraft in the troposphere provide inputs to the model, including observations of the ice nuclei and of the entire size distribution of condensation nuclei.

Homogeneous droplet freezing is found to be the source of almost all of the ice crystals in the anvil updraught of this particular model cloud. Most of the simulated droplets that freeze to form anvil crystals appear to be nucleated by activation of aerosols far above cloud base in the interior of the cloud (‘secondary’ or ‘in‐cloud’ droplet nucleation). This is partly because primary droplets formed at cloud base are invariably depleted by accretion before they can reach the anvil base in the updraught, which promotes an increase with height of the average supersaturation in the updraught aloft. More than half of these aerosols, activated far above cloud base, are entrained into the updraught of this model cloud from the lateral environment above about 5 km above mean sea level. This confirms the importance of remote sources of atmospheric aerosol for anvil glaciation.

Other nucleation processes impinge indirectly upon the anvil glaciation by modifying the concentration of supercooled droplets in the upper levels of the mixed‐phase region. For instance, the warm‐rain process produces a massive indirect impact on the anvil crystal concentration, because it determines the mass of precipitation forming in the updraught. It competes with homogeneous freezing as a sink for cloud droplets. The effects from turbulent enhancement of the warm‐rain process and from other nucleation processes on the anvil ice properties are assessed. Copyright © 2005 Royal Meteorological Society.
Can error source terms in forecasting models be represented as Gaussian Markov noises?
Authors: Nicolis C.
Published: July 2005

The repercussions of model error on the long term climatological means and on the variability around them are analysed. The extent to which a stochastic representation of error source terms provides a universal correcting mechanism is addressed. General relations are derived linking the model error to the climatological means and the variability properties of a forecasting model subjected to a correcting Gaussian Markov noise on the basis of moment equations associated with Fokker–Planck and Liouville type equations. These relations are implemented in a variety of models giving rise to regular and to chaotic solutions. As it turns out, forecasting models fall into distinct universality classes differing in their response to the effect of noise according to the structure of the Jacobian and the Hessian matrices of the model phase‐space velocity. It is concluded that different trends may exist in which the ‘correcting’ noise tends to depress or, on the contrary, amplify the model error. Copyright © 2005 Royal Meteorological Society.
Major Utilization of Natural Gas in Turkey
Authors: Kilic Ahmet Mahmut
Published: July 2005

The aim of this paper is the major utilization of natural gas in Turkey. Turkey is rapidly growing in terms of both its economy and population due to its demand for energy. In the new world energy order, gas usage with no doubt will continue to grow well into the 21st century. Natural gas has been available for Turkish consumption for 17 years. Its use expanded sharply after the signing of the first sales and purchase agreement with the former Soviet Union in 1986. Turkish natural gas usage is projected to increase remarkably in coming years, with the prime consumers, expected to be industry and power plants. Energy demand of Turkey is growing by 8% annually, one of the highest rates in the world. In addition, natural gas consumption is the fastest growing primary energy source in Turkey. Gas sales started at 0.5 bcm (billion cubic meters), in 1987 and reached approximately 22 bcm in 2003. Turkey is an important candidate to be the “energy corridor” in the transmission of the abundant oil and natural gas resources of the Middle East and Middle Asia countries to the Western market.
Leakage up Faults: Production and Supply Concerns for “Topping Up” Sands
Authors: Lerche Ian
Published: July 2005

This paper discusses the leakage of hydrocarbons up a fault into an overlying sand that is cut by the fault. The supply of hydrocarbons is continuous until exhaustion of the main source below the sand. At the same time that hydrocarbons can be filling the sand, production is also allowed from the sand components. Hydrocarbons may also bypass either or both components of the cut sand if their respective capacities have been reached, so that there can be a time dependent loss from the lower sand component or the upper sand component or both, as they are filled and drained by production. Numerical illustrations show how the start time of production for each sand influences the bypass and “topping-up” of the sands, as well as the influence of the fractions of the hydrocarbon flow that can be diverted to each of the sand components of the hydrocarbon flow are allowed to vary. In short, an Excel program built upon such ideas has many of the capabilities needed to describe the broad features of leakage, production, topping up, and loss from such sands, as occur specifically in the Eugene Island 335 field as well as in many other fields.
Hydrocarbon Flow along Intersecting Faults
Authors: Lerche Ian
Published: July 2005

This paper is concerned with the channeling of hydrocarbon flow up a master fault and the diversion of the flow to the left or right at the intersection of the master fault with a second fault. In particular, when reservoirs of different capacities can exist on the master fault and the secondary fault, the question of the retention efficiency of the reservoirs to the hydrocarbon flow is of interest. In addition, given the customary lack of sharp knowledge of the hydrocarbon petroleum system before drilling, the influence of uncertainties in the flow and reservoir properties is discussed in terms of statistical probabilistic representations and the dominant components to the uncertainties of retention and/or bypass are addressed. There is no consideration given in this paper to the possibility of production from the reservoirs before, during, or after fill by the hydrocarbons being supplied along the faults. That problem will be addressed in the next paper.
Leakage along Faults: Capture by an Overlying Sand
Authors: Lerche Ian
Published: July 2005

This paper considers the capability of a sand, cut by a fault, to capture hydrocarbons supplied from below along a fault. The volume supplied, the capacity of each part of the sand, and the fractions of volume supplied that could be diverted to each sand, are all significant influences on the amounts of hydrocarbons that could be captured. Simple deterministic examples are given to illustrate the patterns of response that ensue when individual parameters are varied, including the amount of hydrocarbons lost from the system. In addition, when all of the parameters can be uncertain, as is most usually the situation when undertaking hydrocarbon exploration estimates of possible reserves, Monte Carlo calculations are used to show which of the uncertain parameters is causing the largest fraction of uncertainty on the fill and loss amounts from the system. In this way one can determine where to expend effort to narrow down the range of uncertainty of the parameters causing the dominant contributions to fill and loss uncertainty, with out having to spend inordinate amounts of time and effort in attempts to determine parameter ranges better for those parameters that hardly influence the uncertainty on hydrocarbon fill and loss.
Usage of Energy Sources and Environmental Problems
Authors: Balat Mustafa
Published: July 2005

This article deals with use of global energy sources and their environmental impacts. The energy sources have been split into three categories: fossil fuels (oil-coal-natural gas), renewable sources, and nuclear sources. Oil and gas are expected to continue to be important sources of energy. New efficient and cost-effective small-scale renewable energy generation options are commercially available today. The share of renewable energy sources is expected to increase very significantly. Recently, environmental problems resulting from energy production, conversion, and utilization have caused increased public awareness in all sectors of the public, industry, and government in both developed and developing countries. The environmental impact of energy use can be seen in two ways: The utilization of limited natural resources and the stress caused by environmental pollution. To combat that environmental damage, exploring and exploiting the utilization of combustible renewables and waste would be a necessary measure for decreasing the environmental impact of energy use.
Dynamic System Identification Using a Step Input
Authors: Kosaka Manabu , Uda Hiroshi , Bamba Eiichi , Shibata Hiroshi
Published: July 2005

In this paper, we propose a deterministic off-line identification method performed by using input and output data with a constant steady state output response such as a step response that causes noise or vibration from a mechanical system at the moment when it is applied but they are attenuated asymptotically. The method can directly acquire any order of reduced model without knowing the real order of a plant, in such a way that the intermediate parameters are uniquely determined so as to be orthogonal with respect to 0 ∼ N-tuple integral values of output error and irrelevant to the unmodelled dynamics. From the intermediate parameters, the coefficients of a rational transfer function are calculated. In consequence, the method can be executed for any plant without knowing or estimating its order at the beginning.

The effectiveness of the method is illustrated by numerical simulations and also by applying it to a 2-mass system.
Proposed Criteria for Low Frequency Industrial Noise in Residential Communities
Authors: Hessler George F.
Published: July 2005

There is a need in the United States for some Federal or prominent standards organization to publish limits in residential areas for low frequency noise attributable to industrial sources. This paper proposes maximum limits based on experience in investigating and solving low frequency noise problems, principally from open cycle combustion turbine installations The author believes the recommended C-weighted limits in this paper are applicable to most common steady low-frequency noise sources in addition to combustion turbines due to the combined tonal and broadband character of the sound. It is hoped standardizing bodies can add this reference to the larger body of literature to arrive at a workable sorely-needed standard.
Whole Body Vibration Measurements and Calculations of the Daily 8-hour Values in Finnish Working Environments
Authors: Marjanen Ykä
Published: July 2005

The European Union Physical Agents Directive (vibration) sets vibration exposure limits for an employer. The measured values from different work phases should be time weighted and summed together to represent a daily 8-hour exposure value. The directive has two limit values, the daily exposure action value and the daily exposure limit value. For the employer the greatest concern is to comply with the exposure limit value, but also exceeding the action value will cause implications. To calculate the daily 8-hour value is not a simple task, because there are normally several different work phases that the worker does in a normal day. Also the assessment of measurements of the vibration levels have to be made in real working environments. The work phases need to be calculated correctly to get the representative daily value. Also breaks and other non-work operations need to be included. This will make the complete assessment very difficult without proper knowledge. In this study a large number of measurements from different mobile work machines were made to establish whether the daily values would exceed the limit values. Analyses were made using three examples to show how the employer can use the standard and directive to assess the daily exposure values or times. The results were largely dependent on the work pattern and the dominant levels.
Methods for Measuring the Dynamic Stiffness of Resilient Rail Fastenings for Low Frequency Vibration Isolation of Railways, Their Problems and Possible Solutions
Authors: Morison Chris , Wang Anbin , Bewes Oliver
Published: July 2005

Low frequency ground or structure-borne sound and vibration emission from urban rail transport systems can be greatly reduced by reducing the stiffness of the rail fastening. Estimates and models of the efficacy of such systems require accurate measurements of their dynamic stiffness over the frequency range of interest, and European Standards make recommendations for such measurements. This paper describes these methods and their shortcomings when applied to modern complete assemblies with low stiffness, one problem of which is the contribution of inertial forces at frequencies approaching and above the natural resonance of the system. This paper suggests a method for correcting for this inertial force, and tests this correction with the driving point method of dynamic stiffness measurement when applied to the Pandrol VANGUARD resilient rail fastening. The preliminary tests effectively triple the frequency range of valid measurements, a result which could be improved when applied to stiffer systems or with further improvements to the test equipment.
Annoyance of Low Frequency Tones and Objective Evaluation Methods
Authors: Subedi Jishnu K. , Yamaguchi Hiroki , Matsumoto Yasunao , Ishihara Mitsutaka
Published: July 2005

Annoyance of low frequency pure and combined tones was measured in a laboratory experiment. Three low frequency tones at frequencies of 31.5, 50 and 80 Hz at four sound pressure levels, from about 6 dB to 24 dB above average hearing threshold, were selected as pure tones. The combined tones were combinations of two tones: the four levels of 31.5, 50 and 80 Hz tones and a constant level 40 Hz tone. The results showed that the rate of increase in annoyance of pure tones with increase in the sound pressure level was higher at lower frequencies, as reported in previous studies. The results for the combined tones showed that the increase in the annoyance of the combined tone compared to the annoyance of pure tone was dependent on the level difference of the two tones and their frequency separation. These results were compared with the evaluation obtained from different objective methods. The three methods were Moore's loudness model, the low frequency A-weighting and the total energy summation used as objective evaluation methods. Among the methods, the low frequency A-weighting gave the best correlation.
Total Non-Occupational Noise Exposure of Construction Workers
Authors: Neitzel Richard
Published: July 2005

Total non-occupational noise exposure levels were estimated for a group of 266 construction apprentices participating in a longitudinal study of noise and hearing loss. Subjects were interviewed regarding their exposure to “episodic” activities (e.g., concert attendance), and noise levels for these activities were obtained from a literature review. “Routine” activities were assessed using a combination of self-reported activity logs and non-occupational noise dosimetry measurements. Routine and episodic activity exposures were combined into estimated annual Leq exposure levels for the 6760 nominal non-occupational hours in a year (LAeq6760h). The LAeq6760h levels were then transformed into equivalent levels for a 2000 hour exposure period (LA2000hn), which allowed direct comparison to occupational risk criteria.

The median LAeq6760h was 73 dBA, and the median LA2000hn was 78 dBA. Nineteen percent of LA2000hn non-occupational exposures exceeded 85 dBA, the generally recommended occupational limit. Firearms use could not be incorporated into the total noise exposure estimates. However, firearms users reported more exposure to other noisy non-occupational activities than did non-shooters, and had higher estimated exposure levels even without including their firearms exposure.

Non-occupational noise exposures among most construction workers present little additional exposure when compared to their occupational exposures. However, they may contribute significantly to overall exposure in the subset of workers who frequently participate in selected noisy activities.
Hull Disturbing Forces Due to Propeller Sources
Authors: Kinns R. , Pim C.D.
Published: July 2005

An acoustic boundary element model of a modern twin-screw cruise liner is used to show how fluctuating pressures above the propeller, and hull forces that cause ship vibration, change relative to each other with the nature of propeller sources. The low frequency effects of fluctuating loads on the propeller in different directions are compared with the effects of unsteady cavitation. The implications of the results for specification of ship requirements and estimation of ship vibration are discussed.
Failures in the System for Dealing with Low Frequency Noise
Authors: Guest Hazel
Published: July 2005

In the UK low frequency noise is a growing problem and complaints from members of the public are rarely resolved. Environmental Health Officers are given inappropriate guidelines and many do not have the necessary training or equipment. As a result technical misconceptions have become institutionalised, exacerbating the problem. Suggestions for dealing with this situation are offered. There is a need for research into the effects upon the brain caused by very low frequency noise (below about 75 Hz), since these are reported to be particularly distressing.
RNA secondary structure prediction by centroids in a Boltzmann weighted ensemble
Authors: DING YE , CHAN CHI YU , LAWRENCE CHARLES E.
Published: July 2005

Prediction of RNA secondary structure by free energy minimization has been the standard for over two decades. Here we describe a novel method that forsakes this paradigm for predictions based on Boltzmann-weighted structure ensemble. We introduce the notion of a centroid structure as a representative for a set of structures and describe a procedure for its identification. In comparison with the minimum free energy (MFE) structure using diverse types of structural RNAs, the centroid of the ensemble makes 30.0% fewer prediction errors as measured by the positive predictive value (PPV) with marginally improved sensitivity. The Boltzmann ensemble can be separated into a small number (3.2 on average) of clusters. Among the centroids of these clusters, the “best cluster centroid” as determined by comparison to the known structure simultaneously improves PPV by 46.5% and sensitivity by 21.7%. For 58% of the studied sequences for which the MFE structure is outside the cluster containing the best centroid, the improvements by the best centroid are 62.5% for PPV and 31.4% for sensitivity. These results suggest that the energy well containing the MFE structure under the current incomplete energy model is often different from the one for the unavailable complete model that presumably contains the unique native structure. Centroids are available on the Sfold server at http://sfold.wadsworth.org.
The role of ribosome recycling factor in dissociation of 70S ribosomes into subunits
Authors: HIROKAWA GO , NIJMAN ROMANA M. , RAJ V. SAMUEL , KAJI HIDEKO , IGARASHI KAZUEI , KAJI AKIRA
Published: July 2005

Protein synthesis is initiated on ribosomal subunits. However, it is not known how 70S ribosomes are dissociated into small and large subunits. Here we show that 70S ribosomes, as well as the model post-termination complexes, are dissociated into stable subunits by cooperative action of three translation factors: ribosome recycling factor (RRF), elongation factor G (EF-G), and initiation factor 3 (IF3). The subunit dissociation is stable enough to be detected by conventional sucrose density gradient centrifugation (SDGC). GTP, but not nonhydrolyzable GTP analog, is essential in this process. We found that RRF and EF-G alone transiently dissociate 70S ribosomes. However, the transient dissociation cannot be detected by SDGC. IF3 stabilizes the dissociation by binding to the transiently formed 30S subunits, preventing re-association back to 70S ribosomes. The three-factor-dependent stable dissociation of ribosomes into subunits completes the ribosome cycle and the resulting subunits are ready for the next round of translation.
Unorthodox mRNA start site to extend the highly structured leader of retrotransposon Tto1 mRNA increases transposition rate
Authors: BÖHMDORFER GUDRUN , HOFACKER IVO L. , GARBER KARIN , JELENIC SRECKO , NIZHYNSKA VIKTORIA , HIROCHIKA HIROHIKO , STADLER PETER F. , BACHMAIR ANDREAS
Published: July 2005

Retroelement RNAs serve as templates for both translation and reverse transcription into extrachromosomal DNA. DNA copies may be inserted into the host genome to multiply element sequences. This transpositional activity of retroelements is usually restricted to specific conditions, particularly to conditions that impose stress on the host organism. In this work, we examined how the mRNA initiation point, and features of primary and secondary structure, of tobacco retrotransposon Tto1 RNA influence its transpositional activity. We found that the most abundant Tto1 RNA is not a substrate for reverse transcription. It is poorly translated, and its 5′-end does not contain a region of redundancy with the most prominent 3′-end. In contrast, expression of an mRNA with the 5′-end extended by 28 nucleotides allows translation and gives rise to transposition events in the heterologous host, Arabidopsis thaliana. In addition, the presence of extended hairpins and of two short open reading frames in the 5′-leader sequence of Tto1 mRNA suggests that translation does not involve ribosome scanning from the mRNA 5′-end to the translation initiation site.
Nop53p is required for late 60S ribosome subunit maturation and nuclear export in yeast
Authors: THOMSON EMMA , TOLLERVEY DAVID
Published: July 2005

We report that Ypl146cp/Nop53p is associated with pre-60S ribosomal complexes and localized to the nucleolus and nucleoplasm. In cells depleted of Nop53p synthesis of the rRNA components of the 60S ribosomal subunit is severely inhibited, with strikingly strong accumulation of the 7S pre-rRNA and a 5′ extended form of the 25S rRNA. In cells depleted of Nop53p pre-60S subunits accumulate in the nucleus. However, a heterokaryon assay demonstrated that Nop53p is not transferred between nuclei, indicating that it is not released into the cytoplasm. We conclude that Nop53p is a late-acting factor in the nuclear maturation of 60S ribosomal subunits, which is required for normal acquisition of export competence. The strong accumulation of preribosomes in the Nop53p-depleted strain further suggests that it may participate in targeting aberrant preribosomes to surveillance and degradation pathways.
Ribavirin is not a functional mimic of the 7-methyl guanosine mRNA cap
Authors: YAN YIFEI , SVITKIN YURI , LEE JOSEPH M. , BISAILLON MARTIN , PELLETIER JERRY
Published: July 2005

Ribavirin is a guanosine ribonucleoside analog that displays broad-spectrum anti-viral activity and is currently used for the treatment of some viral infections. Ribavirin has recently been proposed to also be a mimic of the 7-methyl guanosine cap found at the 5′ end of mRNAs. To obtain supporting functional data for this hypothesis, we assessed the ability of ribavirin triphosphate to interfere with the interaction between eIF4E and 7-methyl guanosine capped mRNA. In chemical cross-linking assays, cap-affinity chromatography, and cap-dependent translation assays, ribavirin was unable to function as a cap analog.
The bipartite structure of the tRNA m1A58 methyltransferase from S. cerevisiae is conserved in humans
Authors: OZANICK SARAH , KRECIC ANNETTE , ANDERSLAND JOSHUA , ANDERSON JAMES T.
Published: July 2005

Among all types of RNA, tRNA is unique given that it possesses the largest assortment and abundance of modified nucleosides. The methylation at N1 of adenosine 58 is a conserved modification, occurring in bacterial, archaeal, and eukaryotic tRNAs. In the yeast Saccharomyces cerevisiae, the tRNA 1-methyladenosine 58 (m1A58) methyltransferase (Mtase) is a two-subunit enzyme encoded by the essential genes TRM6 (GCD10) and TRM61 (GCD14). While the significance of many tRNA modifications is poorly understood, methylation of A58 is known to be critical for maintaining the stability of initiator tRNAMet in yeast. Furthermore, all retroviruses utilize m1A58-containing tRNAs to prime reverse transcription, and it has been shown that the presence of m1A58 in human tRNA3Lys is needed for accurate termination of plus-strand strong-stop DNA synthesis during HIV-1 replication. In this study we have identified the human homologs of the yeast m1A Mtase through amino acid sequence identity and complementation of trm6 and trm61 mutant phenotypes. When coexpressed in yeast, human Trm6p and Trm61p restored the formation of m1A in tRNA, modifying both yeast initiator tRNAMet and human tRNA3Lys. Stable hTrm6p/hTrm61p complexes purified from yeast maintained tRNA m1A Mtase activity in vitro. The human m1A Mtase complex also exhibited substrate specificity—modifying wild-type yeast tRNAiMet but not an A58U mutant. Therefore, the human tRNA m1A Mtase shares both functional and structural homology with the yeast tRNA m1A Mtase, possessing similar enzymatic activity as well as a conserved binary composition.
Molecular mimicry: Quantitative methods to study structural similarity between protein and RNA
Authors: LIANG HAN , LANDWEBER LAURA F.
Published: July 2005

With rapidly increasing availability of three-dimensional structures, one major challenge for the post-genome era is to infer the functions of biological molecules based on their structural similarity. While quantitative studies of structural similarity between the same type of biological molecules (e.g., protein vs. protein) have been carried out intensively, the comparable study of structural similarity between different types of biological molecules (e.g., protein vs. RNA) remains unexplored. Here we have developed a new bioinformatics approach to quantitatively study the structural similarity between two different types of biopolymers—proteins and RNA—based on the spatial distribution of conserved elements. We applied it to two previously proposed tRNA–protein mimicry pairs whose functional relatedness between two molecules has been recently determined experimentally. Our method detected the biologically meaningful signals, which are consistent with experimental evidence.