High-precision diode-laser-based temperature measurement for air refractive index compensation

We present a laser-based system to measure the refractive index of air over a long path length. In optical distance measurements it is essential to know the refractive index of air with high accuracy. Commonly, the refractive index of air is calculated from the properties of the ambient air using either Ciddor or Edlén equations, where the dominant uncertainty component is in most cases the air temperature. The method developed in this work utilises direct absorption spectroscopy of oxygen to measure the average temperature of air and of water vapor to measure relative humidity. The method allows measurement of temperature and humidity over the same beam path as in optical distance measurement, providing spatially well matching data. Indoor and outdoor measurements demonstrate the effectiveness of the method. In particular, we demonstrate an effective compensation of the refractive index of air in an interferometric length measurement at a time-variant and spatially non-homogenous temperature over a long time period. Further, we were able to demonstrate 7 mK RMS noise over a 67 m path length using 120 s sample time. To our knowledge, this is the best temperature precision reported for a spectroscopic temperature measurement.

On the two dimensional effective electron mass in quantum wells, inversion layers and NIPI superlattices of Kane type semiconductors in the presence of strong light waves: Simplified theory and relative comparison

An attempt is made to study the two dimensional (2D) effective electron mass (EEM) in quantum wells (Qws), inversion layers (ILs) and NIPI superlattices of Kane type semiconductors in the presence of strong external photoexcitation on the basis of a newly formulated electron dispersion laws within the framework of k.p. formalism. It has been found, taking InAs and InSb as examples, that the EEM in Qws, ILs and superlattices increases with increasing concentration, light intensity and wavelength of the incident light waves, respectively and the numerical magnitudes in each case is band structure dependent. The EEM in ILs is quantum number dependent exhibiting quantum jumps for specified values of the surface electric field and in NIPI superlattices; the same is the function of Fermi energy and the subband index characterizing such 2D structures. The appearance of the humps of the respective curves is due to the redistribution of the electrons among the quantized energy levels when the quantum numbers corresponding to the highest occupied level changes from one fixed value to the others. Although the EEM varies in various manners with all the variables as evident from all the curves, the rates of variations totally depend on the specific dispersion relation of the particular 2D structure. Under certain limiting conditions, all the results as derived in this paper get transformed into well known formulas of the EEM and the electron statistics in the absence of external photo-excitation and thus confirming the compatibility test. The results of this paper find three applications in the field of microstructures. (C) 2011 Elsevier Ltd. All rights reserved.

A New Voltage Stability Index based on the Tangent Vector of the Power Flow Jacobian

This paper presents a new voltage stability index based on the tangent vector of the power flow jacobian. This index is capable of providing the relative vulnerability information of the system buses from the point of view of voltage collapse. In an effort to compare this index with a similar index, the popular voltage stability index L is studied and it is shown through system studies that the L index is not a very consistent indicator of the voltage collapse point of the system but is only a reasonable indicator of the vulnerability of the system buses to voltage collapse. We also show that the new index can be used in the voltage stability analysis of radial systems which is not possible with the L index. This is a significant result of this investigation since there is a lot of contemporary interest in distributed generation and microgrids which are by and large radial in nature. Simulation results considering several test systems are provided to validate the results and the computational needs of the proposed scheme is assessed in comparison with other schemes

An examination of fluctuations in the “concentration index” of purse seiners and baitboats in the fishery for tropical tunas in the Eastern Pacific, 1951-1961

ENGLISH: In the eastern Pacific Ocean nearly all of the commercial catches of yellowfin tuna (Thunnus albacares) and skipjack (Katsuwonus pelamis) are taken by two types of vessels, baitboats, which use pole and line in conjunction with live-bait, and purse-seiners. From its inception until very recently (1959), this fishery was dominated by baitboats. This method of fishing has been described by Godsil (1938) and Shimada and Schaefer (1956). From 1951 through 1958 baitboats caught between 66.4 and 90.8 per cent of the yellowfin and between 87.2 and 95.3 per cent of the skipjack landed by the California-based fleet. These vessels fished for tuna throughout the year and covered virtually all of the area from southern California to northern Chile. The purse-seine fishery for tunas developed out of the round-haul net fisheries for California sardines and other species. Scofield (1951) gives a detailed description of the development of gear and fishing methods. Prior to 1959 many of the seiners engaged in other fisheries during the fall and early winter months and consequently most of the fishing effort for tuna occurred in the period February-August. The vessels were quite small, averaging approximately 120 tons carrying capacity (Broadhead and Marshall, 1960), in comparison to the baitboats, of which the most numerous size-class was 201-300 tons. The seiners were naturally more restricted in range than the baitboats and most of their effort was restricted to the northern grounds. During the period 1959-61 most of the large baitboats were converted for purse-seining and the existing seiner fleet was modernized. These developments increased the range of the seiner fleet and resulted in a wider and more nearly even spatial and temporal distribution of effort. By the early part of 1961, the purse-seine fleet approximated the level of the preconversion baitboat fleet in amount of effort applied and area covered. The changes in the purse-seine fishery and the fishing methods employed in the modernized fleet are described by Orange and Broadhead (1959), Broadhead and Marshall (1960), McNeely (1961) and Broadhead (1962). The change in the relative importance of the two gears is illustrated by the decline in the proportion of the total logged tonnage landed by California-based baitboats, in comparison to the proportion landed by seiners. In 1959 baitboats landed 49.5 per cent of the yellowfin and 87.8 per cent of the skipjack. In 1960 these percentages were 22.9 and 74.7 respectively and in 1961 the decline continued to 12.6 per cent of the yellowfin and 30.0 per cent of the skipjack (Schaefer, 1962). In previous Bulletins of this Commission (Griffiths, 1960; Calkins, 1961) the baitboat catch and effort statistics were used to compute two indices of population density and an index of concentration of fishing effort and the fluctuations of these indices were analyzed in some detail. Due to the change in the relative importance of the two gears it is appropriate to extend this investigation to include the purse-seine data. The objectives of this paper are to compute two indices of population density and an index of concentration of fishing effort and to examine the fluctuations in these indices before and after the changes in the fishery. A further objective is to compare the purse-seine indices with those of the baitboats for the same time periods. SPANISH: En el Océano Pacífico Oriental casi todas las capturas comerciales del atún aleta amarilla (Thunnus albacares) y del barrilete (Katsuwonus pelamis) son efectuadas por dos tipos de barcos, los barcos de carnada que emplean la caña y el anzuelo en conjunto con la carnada viva, y los barcos rederos. Desde su comienzo hasta hace poco tiempo (1959), esta pesquería estaba dominada por los barcos de carnada. El método de pesca usado por estos barcos ha sido descrito por Godsil (1938) y por Shimada y Schaefer (1956). De 1951 a 1958, los barcos de carnada pescaron entre el 66.4 y el 90.8 por ciento del atún aleta amarilla y entre el 87.2 y el 95.3 por ciento del barrilete descargados por la flota que tiene su base en California. Estos barcos pescaron atún durante todo el año y cubrieron virtualmente toda el área de California meridional hasta la parte norte de Chile. La pesquería del atún con redes de cerco se originó en las pesquerías de las sardinas de California y otras especies, con redes que se remolcaban circularmente. Scofield (1951) dá una descripción detallada del desarrollo de los métodos y del equipo de pesca. Antes de 1959 muchos de los rederos se dedicaban a otras pesquerías durante los meses del otoño y a principios del invierno y consecuentemente, la mayor parte del esfuerzo depesca para la producción del atún ocurría en el período febrero-agosto. Las embarcaciones eran bastante pequeñas, con un promedio de aproximadamente 120 toneladas de capacidad para el transporte (Broadhead y Marshall, 1960) en comparación con los barcos de carnada, de los cuales la clase de tamaño más numerosa era de 201 a 300 toneladas. Los rederos estaban naturalmente más restringidos en su radio de acción que los barcos de carnada y la mayor parte de su esfuerzo se limitaba a las localidades del norte. Durante el período 1959-61, la mayoría de los grandes barcos de carnada fueron convertidos al sistema de pesca con redes de cerco, y se modernizó la flota existente de los rederos. Estos cambios aumentaron el alcance de la flota de los barcos rederos dando como resultado una distribución más amplia y casi más uniforme del esfuerzo espaciado y temporal. En la primera parte del año 1961, la flota de rederos se aproximó al nivel de la preconversión de la flota de clipers, en la cantidad de esfuerzo aplicado y al área comprendida. Los cambios en la pesquería con red y los métodos de pesca empleados en la flota modernizada, han sido descritos por Orange y Broadhead (1959), Broadl1ead y Marshall (1960), McNeely (1961) y Broadhead (1962). El cambio en la importancia relativa de los dos sistemas de pesca está ilustrado por la declinación en la proporción del tonelaje total registrado, como descargado por los barcos de carnada que tienen su base en California, comparado con la proporción desembarcada por los barcos rederos. En 1959 los clipers descargaron el 49.5 por ciento del atún aleta amarilla y el 87.8 por ciento del barrilete. En 1960 estos porcentajes fueron del 22.9 y 74.7 respectivamente, y en 1961 continuó la reducción hasta el 12.6 por ciento del atún aleta amarilla y el 30.0 por ciento del barrilete (Schaefer, 1962). En Boletines anteriores de la Comisión (Griffiths, 1960; Calkins, 1961) las estadísticas de la pesca y el esfuerzo de los clipers se utilizaron para computar dos índices de la densidad de población y un índice de la concentración del esfuerzo de pesca, y se analizaron algo detalladamente las fluctuaciones de estos índices. Debido al cambio en la importancia relativa de los dos sistemas de pesca, es conveniente extender esta investigación para incluir los datos correspondientes a los barcos rederos. Los objetivos del presente estudio son de computar dos índices de la densidad de población y un índice de la concentración del esfuerzo de pesca, y examinar las fluctuaciones en estos índices, antes y después de los cambios en la pesquería. Otro objetivo es de comparar los índices de los barcos rederos, con aquellos de los clipers en los mismos períodos de tiempo.

Phase control of switching from positive to negative index material in a four-level atomic system

Electric and magnetic responses of the medium to the probe field are analysed in a four-level loop atomic system by taking into account the relative phase of the applied fields. An interesting phenomenon is found: under suitable conditions, a change of the refractive index from positive to negative can occur by modulating the relative phase of the applied fields. Then the medium can be switched from a positive index material to a negative index material in our scheme. In addition, a negative index material can be realized in different frequency regions by adjusting the relative phase. It may give us a convenient way to obtain the desired material with positive or negative index.

Effects of relative phase in an open ladder system without incoherent pumping

We studied effects of the relative phase between the probe and driving fields on the absorption and dispersion properties in an open three-level ladder system with spontaneously generated coherence but without incoherent pumping. It is shown that by the phase controlling, switching from absorption to lasing without inversion (LWI) and enhancing remarkablely LWI gain can be realized; large index of refraction with zero absorption and the electromagnetically induced transparency can be obtained. We also find that varying the atomic injection and exit rates has a considerable influence on the phase dependent-absorption property of the probe field, existent of the atomic injection and exit rates gives the necessary condition of the realization of LWI, getting LWI is impossible in the corresponding closed system without incoherent pumping. We studied effects of the relative phase between the probe and driving fields on the absorption and dispersion properties in an open three-level ladder system with spontaneously generated coherence but without incoherent pumping. It is shown that by the phase controlling, switching from absorption to lasing without inversion (LWI) and enhancing remarkablely LWI gain can be realized; large index of refraction with zero absorption and the electromagnetically induced transparency can be obtained. We also find that varying the atomic injection and exit rates has a considerable influence on the phase dependent-absorption property of the probe field, existent of the atomic injection and exit rates gives the necessary condition of the realization of LWI, getting LWI is impossible in the corresponding closed system without incoherent pumping.

High Er3+ concentration low refractive index fluorophosphate glass for evanescent wave optical amplifiers

This is about the first reported laser glass with very low no, high Er3+ concentration and no quenching. In this work, a series of high Er3+ concentration (10.6-12.2 x 10(20) ions/cm(3)), low refractive index (n(1550) < 1.47) and relatively high fluorescence lifetime (6.8-12.6 ms) fluorophosphate glasses were made. A cw-pumping evanescent wave optical amplifier experiment was performed with it, and a relative gain of around 2dB at 1550 nm wavelength was achieved while the noise level was almost unchanged. To our knowledge, this is the first successful relative gain in evanescent wave optical amplifiers (EWOA) demonstrated with cw pumping. It is a valuable study of specially designed fluorophosphate glass suitable for EWOA communication experiment. (C) 2008 Elsevier B.V. All rights reserved.

Influence of climate on environmental factors associated with long-term changes in chlorophyll production for the Sacramento-San Joaquin delta and Suisun Bay, California

Long-term changes in chlorophyll production were predicted from environmental variables for the Sacramento and San Joaquin rivers and Suisun Bay using Box-Jenkins transfer function models. Data used for the analyses were collected semimonthly or monthly between 1971 and 1987. Transfer function models developed to describe changes in chlorophyll production over time as a function of environmental variables were characterized by lagged responses and described between 39 and 51 percent of the data variation. Significant correlations between environmental variables and the California climate index (CA SLP) were used to develop a conceptual model of the link between regional climate and estuarine production.

Refractive index evaluation of multi-walled carbon nanotube arrays

Transmission terahertz time-domain spectroscopy (THz-TDS) measurements of carbon nanotube arrays are presented. A relatively thin film with vertically aligned multi-walled carbon nanotubes has been prepared and measured using THz-TDS. Experimental results were obtained from 80GHz to 2.5THz, and the sample has been characterized by extracting the relative permittivity of the carbon nanotubes. A combination of the Maxwell-Garnett and Drude models within the frequency range provide a good fit to the measured permittivity.

Trophic State Index, morphoedaphic index and fish yield prediction in a sub-tropical lake, Manchar (Sindh), Pakistan

Limnological factors of a sub-tropical lake Manchar were studied on seasonal basis. The mean values of various parameters were: transparency, (secchi disc reading): 90.5 cm, Orthophosphate: 0.257 mg/l, TDS: 3310,5 mg/l, Conductivity: 5232 µs/l, Total Chlorophyll (Planktonic): 31.3 µg/l Planktonic biomass: 5466 µg/l. Trophic state index (TSI) was calculated by using Carlson's (1977) equations. Mean TSI for transparency was 61, while for orthophosphate and chlorophyll, it was 82 and 64 respectively. TSI values indicate advanced eutrophic state of Manchar Lake. Morphoedaphic index (MEI) was also calculated on seasonal basis. The mean values were, TDS: 1103, conductivity: 1744, alkalinity: 60, transparency: 29 and biomass (plankton dry weight): 1746. Fish yield prediction for Manchar Lake (Z =3m, mean area=100 km²) was calculated by using MEI values. The results were quite different among various parameters. Conductivity (89.1mt/y), biomass (67.6 mt/y) and TDS (44.6 mt/y) were found to be good predictors of fish yield. Chlorophyll, transparency and alkalinity values gave very low estimate.

Temporal Coherence of Chlorophyll a during a Spring Phytoplankton Bloom in Xiangxi Bay of Three-Gorges Reservoir, China

Algal bloom phenomenon was defined as "the rapid growth of one or more phytoplankton species which leads to a rapid increase in the biomass of phytoplankton", yet most estimates of temporal coherence are based on yearly or monthly sampling frequencies and little is known of how synchrony varies among phytoplankton or of the causes of temporal coherence during spring algal bloom. In this study, data of chlorophyll a and related environmental parameters were weekly gathered at 15 sampling sites in Xiangxi Bay of Three-Gorges Reservoir (TGR, China) to evaluate patterns of temporal coherence for phytoplankton during spring bloom and test if spatial heterogeneity of nutrient and inorganic suspended particles within a single ecosystem influences synchrony of spring phytoplankton dynamics. There is a clear spatial and temporal variation in chlorophyll a across Xiangxi Bay. The degree of temporal coherence for chlorophyll a between pairs of sites located in Xiangxi Bay ranged from -0.367 to 0.952 with mean and median values of 0.349 and 0.321, respectively. Low levels of temporal coherence were often detected among the three stretches of the bay (Down reach, middle reach and upper reach), while high levels of temporal coherence were often found within the same reach of the bay. The relative difference of DIN between pair sites was the strong predictor of temporal coherence for chlorophyll a in down and middle reach of the bay, while the relative difference in Anorganic Suspended Solids was the important factor regulating temporal coherence in middle and upper reach. Contrary to many studies, these results illustrate that, in a small geographic area (a single reservoir bay of approximately 25 km), spatial heterogeneity influence synchrony of phytoplankton dynamics during spring bloom and local processes may override the effects of regional processes or dispersal.

EFFECT OF ELEVATED BICARBONATE CONCENTRATION ON GROWTH, CHLOROPHYLL A FLUORESCENCE AND ULTRA-STRUCTURE OF Microcystis aeruginosa (CYANOBACTERIUM)

The influence of bicarbonate (HCO3-) on Microcystis aeruginosa FACHB 905 was assessed in this study. Growth curves, chlorophyll a fluorescence and ultrastructure were measured at two HCO3- concentrations, 2.3 mM and 12.4 mM. A treatment of sodium chloride (NaCl) was also conducted alongside to establish the influence level of sodium. It was found that upon treatment with elevated HCO3- concentrations of 2.3 mM and 12.4 mM, cell densities were 13% and 27% (respectively) higher than controls. In photosynthetic performance, elevated HCO3- concentration initially stimulated Fv/Fm at the prophase of culture and then subsequently inhibited it. The inhibition of 2.3mM was higher than that of 12.4mM HCO3-. The maximum relative electron transport rate (ETRmax) exhibited inhibition at elevated HCO3- concentrations. DI0/CS was decreased at 2.3 mM and increased at 12.4mM. In the case of both treatments. ABS/CSI TR0/CS, ET0/CS, RC/CS0 and RC/CSm were decreased by elevated HCO3- concentrations, which indicated damage to photosynthetic apparati and an inactivation of a fraction of reaction centers. This point was also proven by ultrastructural photos. High HCO3--exposed cells lost the characteristic photosynthetic membrane arrangement compared with the control and high salinity treated samples. At the 2.3mM concentration of HCO3-. damage to photosynthetic apparati caused decreased photosynthetic activity. These findings suggested that elevated HCO3- concentration stimulated the growth and photosynthesis of M. aeruginosa FACHB 905 in a short time. Exposure to high HCO3- concentrations for a longer period of time will damage photosynthetic apparatus. In addition, the ultrastructure indicated that elevated HCO3--concentration lead to photosynthetic apparati damage. In our experiment, it was observed that the inhibition effect of 2.3mM HCO3- was higher than that of 12.4mM HCO3-. We hypothesized that M. aeruginosa FACHB 905 induced a protective mechanism under high concentrations of HCO3-.

TN : TP ratio and planktivorous fish do not affect nutrient-chlorophyll relationships in shallow lakes

1. In previous work, phytoplankton regulation in freshwater lakes has been associated with many factors. Among these, the ratio of total nitrogen to total phosphorus (TN : TP) has been widely proposed as an index to identify whether phytoplankton are N- or P-limited. From another point of view, it has been suggested that planktivorous fish can be used to control phytoplankton. 2. Large-scale investigations of phytoplankton biomass [measured as chlorophyll a, (chl-a)] were carried out in 45 mid-lower Yangtze shallow lakes to test hypotheses concerning nutrient limitation (assessed with TN : TP ratios) and phytoplankton control by planktivorous fish. 3. Regression analyses indicated that TP was the primary regulating factor and TN the second regulating factor for both annual and summer phytoplankton chl-a. In separate nutrient-chl-a regression analyses for lakes of different TN : TP ratios, TP was also superior to TN in predicting chl-a at all particular TN : TP ranges and over the entire TN : TP spectrum. Further analyses found that chl-a : TP was not influenced by TN : TP, while chl-a : TN was positively and highly correlated to TP : TN. 4. Based on these results, and others in the literature, we argue that the TN : TP ratio is inappropriate as an index to identify limiting nutrients. It is almost impossible to specify a 'cut-off' TN : TP ratio to identify a limiting nutrient for a multi-species community because optimal N : P ratios vary greatly among phytoplankton species. 5. Lakes with yields of planktivorous fish (silver and bighead carp, the species native to China) > 100 kg ha(-1) had significantly higher chl-a and lower Secchi depth than those with yields < 100 kg ha(-1). TP-chl-a and TP-Secchi depth relationships are not significantly different between lakes with yields > 100 kg ha(-1) or < 100 kg ha(-1). These results indicate that the fish failed to decrease chl-a yield or enhance Z(SD). Therefore, silver carp and bighead carp are not recommended as a biotic agent for phytoplankton control in lake management if the goal is to control the entire phytoplankton and to enhance water quality.

Attenuation of photosynthetically available radiation by chlorophyll, chromophoric dissolved organic matter, and tripton in lake Donghu, China

The attenuation coefficient of photosynthetically available radiation [K-d(PAR)] and three water quality parameters [chlorophyll a (chl a)], chromophoric dissolved organic matter (CDOM) and tripton] were measured at three stations in shallow, subtropical Lake Donghu from April 2003 to March 2004. The multiple regression equation of K-d(PAR) versus chl a, CDOM, and tripton was: K-d(PAR) = 0.44 + 0.019 chl a + 1.88 CDOM + 0.016 tripton, which revealed the relative contributions of the three parameters to K-d(PAR). The effects of water and CDOM on K-d(PAR) were of minor importance (19-26%), while chl a and tripton were the two greatest contributors, accounting collectively for 74-81%.

Three-stage transformation of chlorophyll transient fluorescence pattern under sustained dehydration and the discovery of critical water content in seaweeds

The chlorophyll fluorescence kinetics of marine red alga Grateloupia turutunt Yamada, green alga Ulva pertusa Kjellm and brown alga Laminaria japonica Aresch during natural sustained dehydration were monitored and investigated. The pulse amplified modulation (PAM) system was used to analyze the distinct fluorescence parameters during thallus dehydration. Results proved that the fluorescence kinetics of different seaweed all showed three patterns of transformation with sustained water loss. These were: 1) peak kinetic pattern (at the early stage of dehydration fluorescence enhanced and quenched subsequently, representing a normal physiological state). 2) plateau kinetic pattern (with sustained water loss fluorescence enhanced continuously but quenching became slower, finally reaching its maximum). 3) Platform kinetic pattern (fluorescence fell and the shape of kinetic curve was similar to plateau kinetic pattern). A critical water content (CWC) could be found and defined as the percentage of water content just prior to the fluorescence drop and to be a significant physiological index for evaluation of plant drought tolerance. Once thallus water content became lower than this value the normal peak pattern can not be recovered even through rehydration, indicating an irreversible damage to the thylakoid membrane. The CWC value corresponding to different marine species were varied and negatively correlated with their desiccation tolerance, for example. Laminaria japonica had the highest CWC value (around 90%) and the lowest dehydration tolerance of the three. In addition, a fluorescence "burst" was found only in red algae during rehydration. The different fluorescence parameters F-o, F-v and F-v, F-m were measured and compared during water loss. Both F-o and F-v increased in the first stage of dehydration but F-v/F-m. kept almost constant. So the immediate response of in vivo chlorophyll fluorescence to dehydration was an enhancement. Later with sustained dehydration F-o increased continuously while F-v decreased and tended to become smaller and smaller. The major changes in fluorescence (including fluorescence drop during dehydration and the burst during rehydration) were all attributed to the change in F-o instead of F-v This significance of F-o indicates that it is necessary to do more research on F-o as well as on its relationship with the state of thylakoid membrane.