How are internal models of unstable tasks formed?

The results of recent studies suggest that humans can form internal models that they use in a feedforward manner to compensate for both stable and unstable dynamics. To examine how internal models are formed, we performed adaptation experiments in novel dynamics, and measured the endpoint force, trajectory and EMG during learning. Analysis of reflex feedback and change of feedforward commands between consecutive trials suggested a unified model of motor learning, which can coherently unify the learning processes observed in stable and unstable dynamics and reproduce available data on motor learning. To our knowledge, this algorithm, based on the concurrent minimization of (reflex) feedback and muscle activation, is also the first nonlinear adaptive controller able to stabilize unstable dynamics.

Studies on cultural conditions of marine Chromatium buderi Truper and Jannasch 1968

Photosynthetic characteristics of a purple sulfur bacterium, Chromatium buderi, cultured under different ranges of pH, temperature, light intensities and ammonium chloride concentrations were examined. Maximum bacteriochlorophyll a synthesis was observed at pH 6.5 whereas the optimum growth was at pH 8.0. In general, higher temperature tended to inhibit the chlorophyll a synthesis and growth. 30°C is the optimum temperature both for chlorophyll a synthesis and growth. At 25µE mˉ²Sˉ¹ the bacteriochlorophyll a content and growth attained maximum level. The response to this low light intensity is an adaptation that ensures a high photosynthetic rate for the purple sulfur bacterium that usually occurs in dimly lit environment. Besides these, ammonium chloride at low concentration enhances both chlorophyll a synthesis and growth. Above 0.5% of it causes the nitrogen-chlorosis and also retards the growth of the bacterium. Possible chemical and structural mechanisms involved are discussed.

Effect of preprocessing storage conditions on the carbonyls of oil sardine

Changes in the total as well as major individual carbonyls of oil sardine muscle during storage at room temperature for 24 h and in crushed ice up to 6 days are reported. Carbonyls extracted with hexane were converted to their 2:4 dinitrophenyl hydrazone (DNPH) derivatives and were separated into major classes by column chromatography on celite/magnesia. Individual carbonyls were then identified by capillary gas chromatography of these derivatives. Though absolute values for carbonyls exhibited wide variations depending upon the degree of freshness, the pattern of changes in the carbonyls during storage of fish under different conditions gave an insight into the influence of carbonyls on flavour. The significance of the findings is discussed.

Effect of stocking density on survival and growth of mud crablings, Scylla sp. in laboratory conditions

Mud crablings, Scylla sp. were reared, for a period of six weeks in fiberglass aquarium under laboratory conditions, to determine the effect of four different stocking densities of 1, 2, 3 and 4 crabling/l of water on their survival and growth. Salinity of water was maintained at 25 ppt throughout the rearing period. Stocking rates of 1, 2, and 3 crabling/l resulted in a similar (p>0.05) survival rates of 75, 74, and 83.5%, respectively, that of 4 crabling/l resulted in significantly lower (p<0.05) survival rate of 56%. No significant difference was observed among different stocking densities in average growth of carapace length (CL), carapace width (CW) and body weight (BW).

Shelf-life of rotary and solar tunnel dried SIS products under different packaging and storage conditions

A study was conducted on the shelf-life of rotary and solar tunnel dried SIS products under different packaging and storage conditions. Organoleptically dried products were found in good condition after a storage period of 60 days in ambient and chilled conditions. The moisture content, TVB-N value and bacterial load slightly increased during 60 days of storage in ambient and chilled conditions. The changes in moisture content and bacterial load were faster in ambient temperature than in chilled storage condition whereas changes in TVB-N value was higher in chilled condition than in ambient temperature. The initial moisture content was in the range of 13.71% to 22.84%. After 60 days of storage in ambient and chilled condition the moisture content of dried products was in the range of 15.09% to 25.11% and 14.49% to 25.01%, respectively. The initial TVB-N value was in the range of 10.64 to 17.52 mg/100g and after 60 days of storage in ambient and chilled condition, TVB-N value was in the range of 29.00 to 34.82 mg/100g and 31.41 to 39.11 mg/100g, respectively. The initial bacterial load was in the range of 1.91x10 super(8) to 2.84x10 super(8) and after 60 days of storage in ambient and chilled condition, the bacterial load was in the range of 6.2x10 super(8) to 1.8x10 super(9) and 5.75x10 super(7) to 5.05x10 super(8) CFU/g, respectively. The results of the present study indicated that it is necessary to store high quality dried products in sealed packed in chilled condition to ensure good quality up to a certain period of time.

Impacts of environmental conditions on macrobenthic distribution along the Suez Gulf, Egypt

Increases in coastal development and human activities leading to sedimentation degrade the quality of water; disturb the natural structure and functions of aquatic communities. The Suez Gulf is a large semi-closed area (~625 km long coastline).The assemblages of bottom fauna were studied qualitatively and quantitatively in the shallow intertidal waters along the western coast of the Suez Gulf. The quality of seawater and sediment structures were analyzed. The distribution of macro-benthos included a total of 38 species of Gastropoda and 9 Bivalvia; and 25 species from the other invertebrates included 7 groups namely, Rhizostoma, Polychaeta, Cirripedia, Amphipoda, Isopoda, Decapoda and Echinodermata. The most dominant group among invertebrate groups was the Polychaeta which included 4 species: Hydroides elegans, Perinereis cultilifera, Perinereis nuntia and Ophelina acuminata. The Cirripedia were represented by 3 species namely, Balanus amphitrite, Chithamalus challengeri and Tetraclita squamosa. The variations in the numerical abundance and biomass of bottom fauna studied between the observation periods and at sampling sites. There was a marked increase in benthos biomass at St. IV (Ras Gharib) yielding an average of 318.8 g/m² in which the gastropod community represented the dominant species in collected samples reaching 270.28 g/m² (84.4% of the total biomass) and numerically numbered 116 ind./m². Veliger larvae of bivalves and gastropods appeared to be present in the plankton for long periods and their production seems to be continuous throughout the year. In the intertidal zone of the Suez Gulf, the values of pH varied within narrow limits. Water temperature and salinity seemed to be important in the distribution and abundance of the macro-benthos communities in the study areas. The organic content in shallow intertidal waters and sediments indicated high values in the central part of the Gulf of Suez.

The study of maturational progress in the whitespotted rabbitfish (Siganus sutor) under different photoperiod and light intensity conditions

The rule of light on the timing of maturation and spawning in tropical and subtropical regions is not clear well, because the reproductive cycle in these systems is lunar synchronized. In this study, thus, the effects of different light regimes were investigated on maturational progress of whitespotted rabbitfish, Siganus sutor, the commercial species in Persian Gulf and Oman Sea. During prespawning season, 50 adult fish were randomly divided into ten 300-l tanks (n=5). The fish in control tank received indoor light condition and the fish in each other tanks were exposed to nine different combinations of photoperiod (8L: 16D, 12L: 12D, 16L: 8D) and light intensity (1000, 2000, 3000 lux). After 60 days, GSI and HSI values, serum levels of estradiol (E2), testosterone (T), 17-α hydroxyprogestrone (OHP), calcium (Ca2+) and gonad histology were evaluated for females and males. In females the GSI mean values of exposed fish increased in comparison with control except for fish were kept under 8L, 2000 lux (tank 8). These differences were significant only for fishes in tank 7 (8L, 3000 lux). In the cases of HSI, the results were converse, so that, the most of thanks showed significant decreasing than fishes reared under indoor condition. Morphology and histology study of Ovaries showed three developmental phases including 3, 4 and chiefly 5 that were parallel with GSI values. Fortheremore the serum levels of E2 was recorded between 0.54-15.8 ng/ml in different fish and their mean values were lower than control in all treatmants (P> 0.05). In males, the similar results were obtained. The GSI and HSI mean values in experimental regimes compared with control were upper and lower, respectively, except for fishes were reared in tank 1 (16L, 3000 lux). Testes histology of fishes were reared under different regimes showed signs of stage 5, since no blood vessels observed and thick milt exuded on slight pressure. The mean values of testosterone consentration in fishes were kept in tanks 1 and 6 (12L, 1000 lux) were higher and in other ones were lower than control group. It is also noted that the OHP and Ca2+ had diverse results including increasing and decreasing mean values than control. So, these factors contrary to E2 and T were not suitable to evaluation of maturity in both sexes. On the basis of ovarian structure in stage 5, oocyte development pattern in this species was group synchronous. So, increased mean of GSI versus decreased values of HSI, E2 and perhaps Ca2+ were the signs of improved maturation. But in males, reduced levels of T and similarity of testes morphology in all samples caused that GSI mean value was the only indicator for differentiating among treatments. These findings suggest that alternations were used in light regimes have been the reason of improved maturity in all treatments except fishes reared in tank 8. The ١٠٧ rule of light intensity on induction of maturity was cleared by comparision between fishes in tanks 4, 5, 6 and control group. Because day length was the same whereas fishes in tanks 4, 5 and 6 were exposed to increased light intensity compared with control. This fact verified by results was obtained from fishes in tanks 9 and especially 7, since photoperiod in this group was lower than control. So, higher intensity was considered as the reason of alternations. Contrasting with indoor condition, Induced maturity was also cleared for fishes were kept in tanks 1, 2 and 3, where both of light duration and intensity were increased. But, the rule of photoperiod was individually demonstrated when obtained results were compared with similar light intensities in other treatments. In conclusion, with comparison among different light regimes it is declared that siganids were kept under light condition of tank 2 including 16h light duration combined with 2000 lux intensity showed the best signs of sexual maturation in both sexes. On the basis of this study, setting up the spring light condition during prespawning season induces maturation in withspotted rabbitfish. This improvement not only by influence of photoperiod or light intensity, separately, but obtained through interaction between them. Thus, determination of threshold and resistance to light be recommended before exposure, although using proper regime during suitable time are necessary to achieve purposes considerably.

Study of effect Rosmarinus officinalis oil and nisin on the growth of Streptococcus iniae in lab conditions and fillets of rainbow trout (Oncorhynchus mykiss)

Fish are an important part of a healthy diet since they contain high quality protein, but typically present a low fat percent when compared to other meats. Fish is an extremely perishable food commodity. On the other hand, food borne diseases are still a major problem in the world, even in well-developed countries. The increasing incidence of food borne diseases coupled with the resultant social and economic implications means there is a constant striving to produce safer food and to develop new antimicrobial agents concerns over the safety of some chemical preservatives and negative consumer reactions to preservatives they perceive as chemical and artificial, have prompted on increased interest in more ‘‘naturalgreen’’ alternatives for the maintenance or extension of product shelf-life. Particular interest has focused on the potential applications of plant essential oils. However, to establish the usefulness of natural antimicrobial preservatives, they must be evaluated alone and in combination with other preservation factors to determine whether there are synergistic effects and multiple hurdles can be devised. In this study, were evaluated the effects of different concentrations of Rosmarinus officinalis and nisin and storage time (15 days) on growth of Streptococcus iniae GQ850377 in a lab conditions and a food model system (fillets of rainbow trout) in 4 and 8 °C. In addition, we also studied multi factorial effects of four different concentration of rosemary, three different concentrations of nisin, two different levels of pH in 3 temperature 4,15 and 37 °C on log% of S.iniae during 43 days in BHI broth. The results on growth of S. iniae were evaluated using SPSS 20.0 statistical software and analyzed the logarithm of total count of the bacterial by Tukey Test. Results were considered statistically significant when P<0.05. MIC and MBC values of rosemary and nisin were 0.03, 0.075 % and 5, 40 μg/mL, respectively. The growth of S. iniae was effected significantly (P<0.05) by rosemary and nisin and also combination of rosemary and nisin in 4 and 8 °C. Samples treated with 0.135 and 0.405 % of rosemary showed a significant decrease on the growth of the bacteria compared with control sample(P<0.05). The most ١٤٦ inhibitory effects were seen in samples treated with 0.135 and 0.405% of rosemary until 9 days after storage. Also, the synergism effects of rosemary and nisin on the growth rate of bacteria was significant (P<0.05) compared with untreated samples and samples treated with the rosemary or nisin, only. Synergistic effects was observed at concentration of 0.405% rosemary and 0.75 μg/mL nisin in both temprature. Results of this study showed that different concentration of rosemary a significant inhibitory effect (P<0.05) on log% of S. iniae, in BHI broth in pH 5.5 and 7 in 4,15 and 37 °C during 43 days. In concentration of 0% rosemary (control) in pH 5.5 and 7 and 37°C, log% were 1.099 and 3.15, whereas in concentration of 0.015% rosemary were -4/241 and 1.454, respectively. The use of essential oils may improve food safety and overall microbial quality. If essential oils were to be more widely applied as antibacterials in foods, the organoleptic impact would be important. In addition, it is recommended to apply essential oils or their compounds as part of a hurdle system and to use it as an antimicrobial component along with other preservation techniques. Thus essential of R. officinalis with high antibacterial activity selected in this study could be a potential source for inhibitory substances against some food-borne pathogens and they may be candidates for using in foods or food-processing systems.

Fluid-structure interaction with mean flow: Over-scattering and unstable resonance growth

It is known theoretically [1-3] that infinitely long fluid loaded plates in mean flow exhibit a range of unusual phenomena in the 'long time' limit. These include convective instability, absolute instability and negative energy waves which are destabilized by dissipation. However, structures are necessarily of finite length and may have discontinuities. Moreover, linear instability waves can only grow over a limited number of cycles before non-linear effects become dominant. We have undertaken an analytical and computational study to investigate the response of finite, discontinuous plates to ascertain if these unusual effects might be realized in practice. Analytically, we take a "wave scattering" [2,4] - as opposed to a "modal superposition" [5] - view of the fluttering plate problem. First, we solve for the scattering coefficients of localized plate discontinuities and identify a range of parameter space, well outside the convective instability regime, where over-scattering or amplified reflection/transmission occurs. These are scattering processes that draw energy from the mean flow into the plate. Next, we use the Wiener-Hopf technique to solve for the scattering coefficients from the leading and trailing edges of a baffled plate. Finally, we construct the response of a finite, baffled plate by a superposition of infinite plate propagating waves continuously scattering off the plate ends and solve for the unstable resonance frequencies and temporal growth rates for long plates. We present a comparison between our computational results and the infinite plate theory. In particular, the resonance response of a moderately sized plate is shown to be in excellent agreement with our long plate analytical predictions. Copyright © 2010 by ASME.