Some effects of Earth's surface on winter jet stream positions in the Northern Hemisphere and rainfall patterns in northern and central California

EXTRACT (SEE PDF FOR FULL ABSTRACT): This report shows that the mean wintertime polar-front jet stream structure consists of three long waves. Prominent ridges in the jet stream flow occur near the longitudes of India, eastern Pacific/west coast of North America, and eastern Atlantic/British Isles; prominent troughs occur near the longitudes of the Middle East, western Pacific, and western Atlantic/east coast of North America. ... One of the climatological ridges occurs along the west coast of North America ... just off the central Oregon coast. The position of the jet stream at this location appears to be the main reason most Pacific storms pass to the north of California. Sustained rainfall in northern and central California occurs only when the storm track is displaced southward of this climatological position.

Studies on the storage behaviour of laminated and commercial Bombay duck

A modified method for the preparation of laminated Bombay duck is presented. Investigation was carried out to find out an effective chemical to control the discoloration of dried laminated Bombay duck. Among various chemicals tried, NDGA and BHT were found to have considerably retarded the discoloration and extended the storage life of the product. Attempt was also made to suggest the optimum humidity level for the proper storage of the commercially dried fish. It was found that a level of about 65% R. H. provided maximum storage life to commercial product.

An automatic focusing and stigmating system for the SEM

A digital minicomputer has been interfaced with a scanning electron microscope, and programmed to control the excitations of the objective lens and the stigmator of the microscope. The electron beam is scanned by a digital scan generator and the digitised video signal is used for computations. To focus the microscope, a parameter related to the 'sharpness' of the image is maximised, and to set the stigmator, the directional information in the above- and below-focus images is used. | A digital minicomputer has been interfaced with a scanning electron microscope, and programmed to control the excitations of the objective lens and the stigmator of the microscope. The electron beam is scanned by a digital scan generator and the digitized video signal is used for computations. To focus the microscope, a parameter related to the 'sharpness' of the image is maximized, and to set the stigmator, the directional information in the above and below-focus images is used.

Spatial emission control of vertical cavity surface emitting lasers to provide bandwidth gain in multimode fibre links using a simple alignment technique

Etched VCSEL sources are reported which avoid bandwidth collapse in multimode fibre using a simple coupling technique to control the launch. These devices have allowed better than over-filled launch bandwidth for alignment tolerances of ±7 microns.

Evaluation of wave drag reduction by flow control

An analytical expression is proposed to estimate the wave drag of an aerofoil equipped with shock control. The analysis extends the conventional approach for a single normal shock wave, based on the knowledge that all types of successful shock control on transonic aerofoils cause bifurcated λ-shock structures. The influence of surface curvature on the λ-shock structure has been taken into account. The extended method has been found to produce fairly good agreement with the results obtained by CFD methods while requiring negligible computational effort. This new formulation is expected to be beneficial in the industrial design process of transonic aerofoils and wings where a large number of computational simulations have to be performed.

Challenges in the Silent Aircraft engine design

The Silent Aircraft Initiative goal is to design an aircraft that is imperceptible above background noise outside the airport boundary. The aircraft that fulfils this objective must also be economically competitive with conventional aircraft of the future and therefore fuel consumption and mechanical reliability are key considerations for the design. To meet these ambitious targets, a multi-fan embedded turbofan engine with boundary layer ingestion has been proposed. This configuration includes several new technologies including a variable area nozzle, a complex high-power transmission system, a Low Pressure turbine designed for low-noise, an axial-radial HP compressor, advanced acoustic liners and a low-speed fan optimized for both cruise and off-design operation. These technologies, in combination, enable a low-noise and fuel efficient propulsion system but they also introduce significant challenges into the design. These challenges include difficulties in predicting the noise and performance of the new components but there are also challenges in reducing the design risks and proving that the new concepts are realizable. This paper presents the details of the engine configuration that has been developed for the Silent Aircraft application. It describes the design approach used for the critical components and discusses the benefits of the new technologies. The new technologies are expected to offer significant benefits in noise reduction without compromising fuel burn. However, more detailed design and further research are required to fully control the additional risks generated by the system complexity.

Micro-ramp control for oblique shock wave / boundary layer interactions

Supersonic engine intakes operating supercritically feature shock wave / boundary layer interactions (SBLIs), which are conventionally controlled using boundary layer bleed. The momentum loss of bleed flow causes high drag, compromising intake performance. Micro-ramp sub-boundary layer vortex generators (SBVGs) have been proposed as an alternative form of flow control for oblique SBLIs in order to reduce the bleed requirement. Experiments have been conducted at Mach 2.5 to characterise the flow details on such devices and investigate their ability to control the interaction between an oblique shock wave and the naturally grown turbulent boundary layer on the tunnel floor. Micro-ramps of four sizes with heights ranging from 25% to 75% of the uncontrolled boundary layer thickness were tested. The flow over all sizes of microramp was found to be similar, featuring streamwise counter-rotating vortices which entrain high momentum fluid, locally reducing the boundary layer displacement thickness. When installed ahead of the shock interaction it was found that the positioning of the micro-ramps is of limited importance. Micro-ramps did not eliminate flow separation. However, the previously two-dimensional separation was broken up into periodic three-dimensional separation zones. The interaction length was reduced and the pressure gradient across the interaction was increased.

Distribution of rDNA in the nucleus of Giardia lamblia - Detection by Ag-I silver stain

OBJECTIVE: To determine whether rDNA of Giardia lamblia forms a nucleolus organizer region (NOR)-like structure and is in a very primitive state. STUDY DESIGN: G lamblia was used as the experimental animal, with Euglena gracilis as the control. The distribution was demonstrated indirectly by the modified Ag-I silver technique, which can specifically indicate the NOR under both light and electron microscopes. RESULTS: In the ultrathin sections of silver-stained Euglena cells, all the silver grains were concentrated in the fibrosa of the nucleolus, while no grains found in the cytoplasm, nucleoplasm, condensed chromosomes or pars granulosa of the nucleus. In the silver-stained Giardia cells, no nucleolus was found; a few silver grains were scattered in the nucleus but were not concentrated in any specific region. CONCLUSION: The distribution of silver grains in G lamblia showed that the transcription of rDNA occurs inside the nucleus, though no nucleolus is present. It is possible that chromosomes are in a very primitive state in diplomonad cells; as each chromosome has few prRNA genes, the transcription is independent of a nucleolus. These results imply that the rDNA of Giardia does not form a NOR-like structure and seems to represent a very primitive state in the evolution of the nucleolus.

Active Voltage Control on series connection of IGBTs and diode recovery optimization

In this paper an Active Voltage Control (AVC) technique is presented, for series connection of insulated-gate-bipolar-transistors (IGBT) and control of diode recovery. The AVC technique can control the switching trajectory of an IGBT according to a pre-set reference signal. In series connections, every series connected IGBT follows the reference and so that the dynamic voltage sharing is achieved. Another key advantage for AVC is that by changing the reference signal at turn-on, the diode recovery can be optimised. © 2010 IEEE.

Soft turn-on of NPT IGBT under Active Voltage Control

In this paper the soft turn-on of NPT IGBT under Active Voltage Control (AVC) is presented. The AVC technique is able to control the IGBT switching trajectory according to a pre-defined reference signal generated by a FPGA chip. By applying a special designed reference signal at turn-on, the IGBT turn-on current overshoot and diode recovery can be optimized. Experiments of soft turn-on with different reference signal are presented in this paper. This technique can be used to reduce the switching stress on the device and on other components of the circuit. © 2011 IEEE.

Socioeconomic assessment of shrimp farming in relation to local livelihoods in the south-west coastal Bangladesh

Nine different categories of stakeholders in shrimp farming industry ·were assessed to show the socioeconomic impact of shrimp farming in south-west Bangladesh. Among all the stakeholders the shrimp farmer's average own land was 4 ha whereas the seed collectors and faria's had lowest amount of average land, 0.1 and 0.5 ha respectively. The shrimp farming positively impacted to the livelihood of stakeholders. Income of the coastal people, sanitation, working facilities of women, employment, health condition and the literacy rate increased due to shrimp farming. On the other hand shrimp farming had negative impact on the rice production, livestock, drinking water supply, and social conflict and violence had increased due to shrimp farming. There were internal conflicts between different stakeholders; the farias conflict with the depot owners and shrimp farmers, marginal farmers' conflict with the rich shrimp farmers about leasing lands and saline water control, the rice farmers conflicts with the shrimp farmers about agricultural crop production.

Use of antibiotics in the preservation of prawn

Effect of incorporating chlorotetracycline (CTC) in ice up to 5 ppm level on the keeping quality of prawns has been studied. A shelf life extension by nearly six days is obtained for the CTC-iced sample over the control. The headless prawns absorbed greater amounts of CTC than whole prawns during storage in CTC-ice. Traces of the antibiotic are found in the muscle of the CTC-iced prawns even after cooking for one hour. The cause of destruction of CTC when used for prawn preservation is discussed.

A phylogeny of Chinese species in the genus Phrynocephalus (Agamidae) inferred from mitochondrial DNA sequences

We investigated the phylogenetic relationships among most Chinese species of lizards in the genus Phrynocephalus (118 individuals, collected from 56 populations of 14 well-defined species and several unidentified specimens) using four mitochondrial gene fragments (12S rRNA, 16S rRNA, cytochrome b, and ND4-tRNA(LEU)). The partition-homogeneity tests indicated that the combined dataset was homogeneous, and maximum-parsimony (MP), neighbor-joining (NJ), maximum-likelihood (ML) and Bayesian (BI) analyses were performed on this combined dataset (49 haplotypes including outgroups for 2058 bp in total). The maximum-parsimony analysis resulted in 24 equally parsimonious trees, and their strict consensus tree shows that there are two major clades representing the Chinese Phrynocephalus species: the viviparous group (Clade A) and the oviparous group (Clade B). The trees derived from Bayesian, ML. and NJ analyses were topologically identical to the MP analysis except for the position of P. mystaceus. All analyses left the nodes for the oviparous group, the most basal clade within the oviparous group, and P. mystaceus unresolved. The phylogenies further suggest that the monophyly of the viviparous species may have resulted from vicariance, while recent dispersal may have been important in generating the pattern of variation among the oviparous species. (C) 2003 Elsevier Science (USA). All rights reserved.

On the development of a mercury-free ternary aluminium anode for cathodic protection

The development of a new mercury-free ternary aluminum anode (CIFTAL) for cathodic protection of marine structures is described. The new anode demonstrated a current efficiency of 83.5% to 85.4% in a current density range of 5.6 to 166.7 mAdmˉ². The current efficiency remained practically stable at 1.4 mAdmˉ² over a test period of 300 days. The service trials of the anode on steel trawlers and aluminum (Indal M 57 S) sheathed wooden boats have shown satisfactory performance in terms of uniform dissolution, current efficiency and driving voltage. In the wake of legislations restricting the use of anodes containing mercury in an endeavor to control the mercury pollution of the near shore aquatic environment, the new anode (CIFTAL) with its stable current output and high current efficiency merits significance in marine cathodic protection.

Reflex contributions to the directional tuning of arm stiffness

It has been shown that during arm movement, humans selectively change the endpoint stiffness of their arm to compensate for the instability in an unstable environment. When the direction of the instability is rotated with respect to the direction of movement, it was found that humans modify the antisymmetric component of their endpoint stiffness. The antisymmetric component of stiffness arises due to reflex responses suggesting that the subjects may have tuned their reflex responses as part of the feedforward adaptive control. The goal of this study was to examine whether the CNS modulates the gain of the reflex response for selective tuning of endpoint impedance. Subjects performed reaching movements in three unstable force fields produced by a robotic manipulandum, each field differing only in the rotational component. After subjects had learned to compensate for the field, allowing them to make unperturbed movements to the target, the endpoint stiffness of the arm was estimated in the middle of the movements. At the same time electromyographic activity (EMG) of six arm muscles was recorded. Analysis of the EMG revealed differences across force fields in the reflex gain of these muscles consistent with stiffness changes. This study suggests that the CNS modulates the reflex gain as part of the adaptive feedforward command in which the endpoint impedance is selectively tuned to overcome environmental instability. © 2008 Springer-Verlag Berlin Heidelberg.