Nursery rearing of Macrobrachium rosenbergii (de Man) using hapa-nets: effects of stocking density

An experiment was conducted in two phases for 45 days each to study the effects of six stocking densities (phase-I: 100, 200 and 300 PL/m² and phase-II: 250, 500 and 750 PL/m²) on growth and survival of Macrobrachium rosenbergii postlarvae (PL) in nylon hapa-nets (1.8m x 1.8m x 1.4m) installed in a pond. Stocking densities of 100, 200 and 300 PL 10/m² resulted in similar (P<0.05) body length (47-48 mm) and survival rate (84-88%), while body weight (0.62g) in PL with 300/m² was significantly lower than that (0.70g) in PL with 100 and 200/m². The growth (body length 47mm and weight 0.64g) and survival (84%) of PL stocked at 250 PL/m² density were significantly higher (P<0.05) than that of PL at 500 and 750/m². Besides the variation in growth and survival in PL at six tests stocking densities, a sharp increase in body weight of PL was observed beginning at the 4th week of rearing.

Dried fish cakes with improved texture

To overcome the problem of underutilization of marine by-catches, Basu et al. (1985) developed fish cube from minced fish meat. Although the product was acceptable, it had little rubbery texture. An attempt was made to improve the texture of the cake by several methods. It was found that 5% tapioca starch along with 3% texturised soybean protein improved the texture and juiciness of the rehydrated product. Preheating of the minced meat at 70°C for 30 minutes also improved the texture appreciably. It was also found that mixing of the ingredients at low speed (less than 100 rpm) in a dough mixer gave the best texture, higher speed and sharp blades leading to rubbery texture. The dehydrated product (moisture 19-20%) thus prepared had a shelf life of six months at ambient temperature.

A model for the erosive wear of rubber at oblique impact angles

A model has been developed to predict the erosive wear behaviour of elastomers under conditions of glancing impact by small hard particles. Previous work has shown the erosive wear mechanism of elastomers under these conditions to be similar in nature to that of abrasive wear by a sharp blade. The model presented here was developed from the model of Southern and Thomas for sliding abrasion, by combining their treatment of the growth of surface cracks with a model for particle impact in which the force - displacement relationship for an idealized flat-ended punch on a semi-infinite elastic solid was assumed. In this way an expression for the erosive wear rate was developed, and compared with experimental measurements of wear rate for natural rubber, styrene - butadiene rubber and a highly crosslinked polybutadiene rubber. Good qualitative agreement was found between the predictions of the model and the experimental measurements. The variation of erosion rate with impact velocity, impact angle, particle size, elastic modulus of the material, coefficient of friction and fatigue properties were all well accounted for. Quantitative agreement was less good, and the effects of erosive particle shape could not be accounted for. The reasons for these discrepancies are discussed. © 1992 IOP Publishing Ltd.

Holographic memory with correlator based readout

The investigation of an inverted hybrid digital/ optical VanderLugt type correlator based on a holographic memory is reported in this paper. A set of reference templates is stored in a photorefractive crystal (PRC) by angular hologram multiplexing. In the filter plane, a phase-modulating liquid crystal television (LCTV) serves as a phase-only input device. During the recognition process, which is based on the pure phase correlation, the reference templates are correlated sequentially with the input object. This correlator shows high sensitivity to object rotation, sharp correlation peaks, high light efficiency, and is fully shift-invariant in spite of the PRC thickness. The influences of the LCTV on the performance of the system are discussed and experimental results are shown.

Measurement of the Mechanical Properties of Filtercakes

In order to improve drilling mud design to cater for specific well situations, a more comprehensive knowledge and understanding of filter cake failure is needed. This paper describes experimental techniques aimed at directly probing the mechanical properties of filter cakes, without having to take into account artefacts due to fluid flow in the substrate. The use of rheometers allows us to determine shear yield stress and dynamic shear modulii of cakes grown on filter paper. A new scraping technique measures the strength and moisture profiles of typical filter cakes with a 0.1 mm resolution. This technique also allows us to probe the adhesion between the filter cake and its rock substrate. In addition, œdometer drained consolidation and unloading of a filter cake give us compression parameters useful for Cam Clay modelling. These independent measurements give similar results as to the elastic modulus of different filter cakes, showing an order of magnitude difference between water based and oil based cakes. We find that these standard cakes behave predominantly as purely elastic materials, with a sharp transition into plastic flow, allowing for the determination of a well-defined yield stress. The effect ofsolids loading on a given type of mud is also studied.

Analytical techniques for indentation of viscoelastic materials

Indentation of linearly viscoelastic materials is explored using elastic-viscoelastic correspondence analysis for both conical-pyramidal and spherical indentation. Boltzmann hereditary integrals are used to generate displacement-time solutions for loading at constant rate and creep following ramp loading. Experimental data for triangle- and trapezoidal-loading are examined for commercially-available polymers and compared with analytical solutions. Emphasis is given to the use of multiple experiments to test the fidelity and predictive capability of the obtained material creep function. Plastic deformation occurs in sharp indentation of glassy polymers and is found to complicate the viscoelastic analysis. A new method is proposed for estimating a material time-constant from peak displacement or hardness data obtained in pyramidal indentation tests performed at different loading rates.

Control of motorcycle steering instabilities

Modern high performance motorcycles often employ a steering damper producing a moment that opposes the angular velocity of the steering assembly relative to the main frame. When modeling the motorcycle in a conventional manner, the steering damper is included as an integral part of the machine. The reduction in the wobble-mode frequency is caused by the effective increase in the steering system's moment of inertia. The compensators show the potential to significantly improve the damping of both wobble and weave modes simultaneously. The dynamic characteristics of high-performance motorcycles can be improved by replacing the conventional steering damper with a passive mechanical steering compensator. The design methodology adopted uses Nyquist frequency response ideas, root-locus analysis and loop-shaping design to obtain a preliminary choice of parameters.

Optimizing the energy output of vertical axis wind turbines for fluctuating wind conditions

The control of a wind turbine to the mean wind speed in a gusty wind results in very poor performance. Fluctuations in wind speed with time constants shorter than the response time of a wind turbine results in operation away from optimum design conditions. The effectiveness of a turbine operating in a gusty wind is shown though the use of an unsteady performance coefficient, C e. This performance coefficient is similar in form to a power coefficient. However in order to accommodate unsteady effects, Ce is defined as a ratio of energy extracted to the total wind energy available over a set time period. The turbine's response to real wind data is modelled, in the first instance, by assuming a constant rotational speed operation. It is shown that a significant increase in energy production can be realized by demanding a Tip Speed Ratio above the steady state optimum. The constant speed model is then further extended to incorporate inertial and controller effects. Parameters dictating how well a turbine can track a demand in Tip Speed Ratio have been identified and combined, to form a non-dimensional turbine response parameter. This parameter characterizes a turbine's ability to track a demand in Tip Speed Ratio dependent on an effective gust frequency. A significant increase in energy output of 42% and 245% is illustrated through the application of this over-speed control. This is for the constant rotational speed and Tip Speed Ratio feedback models respectively. The affect of airfoil choice on energy extraction within a gusty wind has been considered. The adaptive control logic developed enables the application of airfoils demonstrating high maximum L/D values but sharp stalling characteristics to be successfully used in a VAWT design.

Growth of the green mussel, Perna viridis (Linn. 1758), from Moheshkhali Channel of the Bay of Bengai, Bangladesh

Growth of Perna viridis L. inhabiting Moheshkhali jetty of the channel was studied for one year from November, 1990 to October, 1991. The mussel attained 88.12mm±14.69 in length within 12 months with a mean growth rate of 7.34mrnlmonth. Employing von Bertalanffy's growth equation it was found that P. viridis can be 88.43mm, 114.69mm and 121.9lmm at the age of 1, 2 and 3 year respectively. The highest growth rate was recorded during November-April, coinciding with the maximum abundance of phytoplankton and the greatest salinity. The maximum growth rate (99.38%) was recorded at an early stage and was followed by a sharp decline to 4.47%. The growth pattern of P. viridis fitted well with the von Bertalanffy's growth equation.

Comparative study on the toxin production and profiles Raphidophytes at different salinities

PLEASE ALSO CHECK THE FULL TEXT ABSTRACT. Toxin production and toxin profiles of four Raphidophytes grown under different salinities were compared to investigate the influence of salinity on cellular content of neurotoxin. In Chatonella andqua CaTx-1, CaTx-11, and CaTx-111 peaked at 25 pplt with yields of 0.99, 0.42, and 2.90 pg/ceU, but the highest yields (2.35 pg/cell) of CaTx-IV was attained at 30 ppt. On the other hand, Chatonella marina yielded higher proportions of CmTx-1 (0.55 pg/ceH) and CmTx-111 (2.50 pg/cell) at 25 ppt. However, CmTx-IV was present in its highest amount (1.65 pg/cell) at 30 ppt, as seen in C anriqua. A smaH amount of CmTx-11 was also detected at 20-35 ppt. The toxin compositions indicate that H. akashiwo is more sensitive to higher salinities than the other three raphidophytes. Substantial compositional change was observed in case of H. akashiwo. HaTx-11 (corresponding to PbTx-9) was detected only as a trace at 20 and 25 ppt. Toxin HaTx-IV (corresponding to oxidized PbTx-2) was most dominant and peaked at 20 ppt with a yield of 0.3 pg/cell. Considerable amounts of HaTx-1 and III (corresponding to PbTx-2 and 3) were also detected. At higher salinities of above 25 ppt HaTx-11 was not detected. F. japonica gave highest yields of FjTx-11 (PbTx-2) and FjTx-IV (Oxidized PbTx-2) at 20 ppt with yields of 0.95, 1.54 pg/cell while the production of toxic profiles FjTx-1 (PbTx- 1) and FjTx-111 (PbTx-3) peaked at 25 ppt with yields of 0.99, 2.54 pg/ceU. A sharp decrease in all toxins profiles (CaTx, CmTx, HaTX and FjTx) was found at salinities of above 30 ppt.

Gaussian Process Regression Networks

We introduce a new regression framework, Gaussian process regression networks (GPRN), which combines the structural properties of Bayesian neural networks with the non-parametric flexibility of Gaussian processes. This model accommodates input dependent signal and noise correlations between multiple response variables, input dependent length-scales and amplitudes, and heavy-tailed predictive distributions. We derive both efficient Markov chain Monte Carlo and variational Bayes inference procedures for this model. We apply GPRN as a multiple output regression and multivariate volatility model, demonstrating substantially improved performance over eight popular multiple output (multi-task) Gaussian process models and three multivariate volatility models on benchmark datasets, including a 1000 dimensional gene expression dataset.

Evolution and biogeography of talpid moles from continental East Asia and the Japanese islands inferred from mitochondrial and nuclear gene sequences

We sequenced the cytochrome b gene from two little-studied mammal species from the highlands of Southwest China, the long-tailed mole Scaptonyx fusicaudus and the gracile shrew-like mole Uropsilus gracilis. This data was used to examine the phylogenetic r

Selective release of fatty acids during lipid hydrolysis in frozen-stored milk fish (Chanos chanos)

Lipid hydrolysis and the nature of fatty acids lost as a result of lipid hydrolysis in milk fish (Chanos chanos) during frozen storage at -20°C is discussed in this paper. There was a preferential loss of saturated acids during the first three weeks of storage. This was followed by loss of polyunsaturated acids during the next seven weeks. Sharp decrease in the levels of monounsaturated acids was observed from the 10th week of frozen storage. These observations are due to the preferential hydrolysis of phospholipids with relatively high proportion of saturated acids during the first three weeks, followed by the hydrolysis of phospholipids with high proportions of polyunsaturated fatty acids from the 3rd to the 10th week, and finally, predominant hydrolysis of neutral lipids from the 10th week onwards. Storage of fish in the ice prior to freezing was found to accelerate lipid hydrolysis, especially that of neutral lipids, during frozen storage.

A mitogenomic perspective on the ancient, rapid radiation in the Galliformes with an emphasis on the Phasianidae

Background: The Galliformes is a well-known and widely distributed Order in Aves. The phylogenetic relationships of galliform birds, especially the turkeys, grouse, chickens, quails, and pheasants, have been studied intensively, likely because of their close association with humans. Despite extensive studies, convergent morphological evolution and rapid radiation have resulted in conflicting hypotheses of phylogenetic relationships. Many internal nodes have remained ambiguous. Results: We analyzed the complete mitochondrial (mt) genomes from 34 galliform species, including 14 new mt genomes and 20 published mt genomes, and obtained a single, robust tree. Most of the internal branches were relatively short and the terminal branches long suggesting an ancient, rapid radiation. The Megapodiidae formed the sister group to all other galliforms, followed in sequence by the Cracidae, Odontophoridae and Numididae. The remaining clade included the Phasianidae, Tetraonidae and Meleagrididae. The genus Arborophila was the sister group of the remaining taxa followed by Polyplectron. This was followed by two major clades: ((((Gallus, Bambusicola) Francolinus) (Coturnix, Alectoris)) Pavo) and (((((((Chrysolophus, Phasianus) Lophura) Syrmaticus) Perdix) Pucrasia) (Meleagris, Bonasa)) ((Lophophorus, Tetraophasis) Tragopan))). Conclusions: The traditional hypothesis of monophyletic lineages of pheasants, partridges, peafowls and tragopans was not supported in this study. Mitogenomic analyses recovered robust phylogenetic relationships and suggested that the Galliformes formed a model group for the study of morphological and behavioral evolution.