Spectral types fromuvbyβ photometry

New diagrams are presented for the assimilation of MK spectral types withuvby photometry, based upon reddening-free parameters calculated using revised reddening ratios and recently published values of meanuvby colours and indices for a selection of MK spectral types.     

Geochemistry of stratabound scheelite mineralisation and associated calc-silicate rocks from Chitral,NE Hindu Kush,Pakistan

Tungsten mineralisation in the NE Hindu Kush terrain occurs 8 km NW of the Tirich Boundary Zone suture between Karakoram and Eastern Hindu Kush. Scheelite occurs mainly in calc-silicate rocks and subordinately in tourmalinites associated with metasediments at Miniki Gol, Chitral. The investigated area underwent two phases of deformation and was metamorphosed up to sillimanite grade, followed by the emplacement of leucogranite and hydrothermal activity. The mineral assemblages of the calc-silicate rocks, comprising clinozoisite, quartz, calcic-amphibole, plagioclase, chlorite, biotite, calcite, sphene, garnet and scheelite, clearly express a skarn type environment. The coexistence of the scheelite grains with clinozoisite and the occurrence of anomalous values of ZrO₂ and Ta₂O₅ in the scheelite grains imply a genetic link between the scheelite mineralisation and post-magmatic hydrothermal fluids. The enrichment of Zr, Hf, Be, Sn, W, Th, U, Ga, Nb, F and Y along with total REE in the scheelite-bearing calc-silicate rocks compared with the associated metasediments assigns that the rocks at Miniki Gol have undergone a pronounced hydrothermal activity. Strong positive correlations between Zr, Hf, Nb, Y, Ta, F and REE, and the mobility of REE are consistent with this consideration. Aqueous fluid inclusions in the scheelite-bearing calc-silicate rocks display very low salinity, suggesting a mixing of magmatic fluids with meteoric water. The formation of intergrown scheelite and clinozoisite indicates a high pH and CO₂-deficient fluid. The tungsten mineralization may be related to the Miniki Gol leucogranite which occurs at a distance of only 400 m.     

Shifts in multi-decadal sea level trends in the East/Japan Sea over the past 60 years

Data derived from altimetry shows that since 1993 the mean sea level over the East /Japan (EJS) Sea is increasing at a rate of ~3 mm/year, but tide gauge records indicate that a multidecadal reversal trend occurred prior to the early 1980s. We here characterize and quantify the multi-decadal trend of mean sea level in the EJS from the reconstructed sea levels and the in-situ ocean profiles over the past 60 years. Our analysis shows that sea level trends have undergone a shift, revealing a declining trend before the early 1980s, followed by a rising trend from the early 1980s onward with a near basin-wide sea level fluctuation. The trend reversal strongly corresponds to changes in the upper-ocean heat content over the EJS, revealing a negative correlation with the Pacific Decadal Oscillation (PDO) index that correlates negatively with wind stress curl (WSC) in the subtropical North Pacific. The PDO-related WSC, which changes the transport of the western boundary current in the subtropical gyre, may account for the observed trend reversal in the EJS sea level on a multi-decadal time scale.     

Modeling the largest inflow of Changjiang freshwater into the Yellow Sea in 2012 with particle-tracking experiment

Abnormally low-salinity water originating from the Changjiang River (CR) was observed at the central Yellow Sea (YS) in 2012, which was quite unique compared to other years. In this study, the intrusion process of the Changjiang Diluted Water (CDW) into the YS interior was examined using a hindcast simulation (2003–2012) with particle-tracking experiments. The particles representing the behavior of the CDW were released at the CR mouth from May to August, and then tracked. The simulated salinity patterns coincide fairly well with those derived from observations, particularly showing a large low-salinity structure around the central YS in 2012. A substantial intrusion of freshwater into the YS occurred in 2012, and this accounted for approximately 16% of all the released particles in 2012 which is twice as high as the mean average covering the 10 years. According to the trajectories in 2012, the particles took less than 50 days to travel from the mouth to the YS interior and followed mainly two paths toward the YS. One pathway traveled northward to the central entrance of the YS and then reached the western coast of Korea. This pathway was attributed to the strong easterly winds in late June and early August when three consecutive typhoons passed through the YS, which was a unique pattern that is rarely found in other years. The other pathway involved particles trapped along the Jiangsu coast drifting farther to the north up to the Shandon Peninsula against the anticyclonic tidal residual circulations during the passage of typhoons.     

The genesis of emeralds and their host rocks from Swat,northwestern Pakistan: a stable-isotope investigation

Emerald deposits in Swat, northwestern Pakistan, occurring in talc-magnesite and quartz-magnesite assemblages, have been investigated through stable isotope studies. Isotopic analyses were performed on a total of seven emeralds, associated quartz (seven samples), fuchsite (three samples) and tourmaline (two samples) from the Mingora emerald mines. The oxygen isotopic composition ( ¹⁸O SMOW) of emeralds shows a strong enrichment in¹⁸O and is remarkably uniform at + 15.6 ± 0.4 (1,n = 7). Each of the two components of water in emerald (channel and inclusion) has a different range of hydrogen isotopic composition: the channel waters being distinctly isotopically heavier (D = –51 to –32 SMOW) than the other inclusion waters (D = –96 to –70 SMOW). Similarly the oxygen isotopic compositions of tourmaline and fuchsite are relatively constant ( ¹⁸O = + 13 to + 14 SMOW) and show enrichment in¹⁸O. The ¹⁸O values of quartz, ranging from + 15.1 to + 19.1 SMOW, are also high (+ 16.9 ± 1.4 1, n = 7). The meanD of channel waters measured from emerald (–42 ± 6.6 SMOW) and that of fluid calculated from hydrous mineralsD_calculated (–47 ± 7.1 SMOW) are consistent with both metamorphic and magmatic origin. However, the close similarity between the measuredD values of the hydroxyl hydrogen in fuchsite (–74 to –6 SMOW) and tourmaline (–84 and –69 SMOW) with pegmatitic muscovite and tourmaline suggests that the mineralization was probably caused by modified (¹⁸O-enriched) hydrothermal solutions derived from an S-type granitic magma. The variation in the carbon and oxygen isotopic composition of magnesite, locally associated with emerald mineralization, is also very restricted ( ¹³ –3.2 ± 0.7%, PDB; ¹⁸O + 17.9 ± 1.27 SMOW). On the basis of the isotopic composition of fluid ( ¹³C –1.8 ± 0.7 PDB; ¹⁸O + 13.6 ± 1.2 SMOW calculated for the 250-550 °C temperature), it is proposed that the Swat magnesites formed due to the carbonation of previously serpentinized ultramafic rocks by a CO₂-bearing fluid of metamorphic origin.     

Estimating extreme flood magnitude in bedrock-influenced channels using representative reach-based channel resistance data

Extreme flood events are considered by many researchers to be very important in controlling the development of semi‐arid bedrock‐influenced river systems. Accurate gauging of such events is often impossible, however, as gauges are drowned and often damaged during the event. A methodology for estimating flood discharge for bedrock‐influenced channels is presented that reconstructs hydrometric characteristics of the peak flow and relates these to the roughness character of the river channel in question. The method is evaluated using peak water‐surface slope data relating to the extreme floods of February 2000 along the Sabie and Letaba rivers, located respectively in the Mpumalanga and Northern Provinces, South Africa. The data, in the form of strandline measurements, were taken at hydraulically relevant points along the long profile of both rivers. The resultant data are utilised together with published high flow channel resistance figures, based on the channel morphology of the Sabie and Letaba rivers, to generate peak flow estimates for a number of locations along both rivers. Comparisons are made between the frictional discharge peak flow estimates, velocity‐area and hydrologic estimates of peak flow. These comparisons indicate that the method can produce discharge estimates with an accuracy of ±10% and ± 35% respectively.     

Titania precipitation in sapphire containing iron and titanium

Titania, TiO₂, precipitation in natural blue sapphire (Fe, Ti: -Al₂O₃) has been investigated using high resolution and analytical transmission electron microscopy. The structure and habit of the TiO₂ precipitate depends on both the Ti⁴⁺ concentration and the temperature at which the precipitate formed. Tetragonal TiO₂ (Rutile) grows at 1350° C but at 1150° C an orthorhombic non-equilibrium TiO₂ polymorph precipitates. Both TiO₂ polymorphs nucleate in the (0001)s plane as lens shaped discs twinned along their diameter. The crystallographic alignment of each type of TiO₂ precipitate with respect to the -Al₂O₃ host matrix provides a high degree of structural coherency with minimal lattice mismatch. Electron diffraction analysis established the following precipitate/host orientation relationships: tetragonal TiO₂: {011}r {11 07B;100}r(0001)s and 01 r10 0s twinned along the (011)r planeand orthorhombic TiO₂: {021}{11 0}s, {100}(0001)s and 0 2 10 0s twinned along the (021) plane.     

Experimental and numerical studies on the development of a new wave absorber

This paper proposes a new wave absorber made of flexible net structures. To test the efficiency of the proposed water absorber, experiments were done on wave absorbers of various lengths of and the thicknesses of the wave absorber. To perform a numerical modeling of the proposed wave absorber, damping terms were introduced in linearized free-surface boundary conditions. The length and the thickness of the wave absorber were modeled by the length and the coefficient of the damping zones. The boundary element method was adopted to solve the system. Series of experiments were performed to obtain the data for the coefficients of the damping term needed in numerical calculations. The predicted wave heights agreed very closely with those of experiments when the lengths of the incoming waves were within the order of the length of the wave absorber.     

A research on the estimation of coefficient roughness in open channel applying entropy concept

Manning’s roughness coefficient is one of the most important parameters in establishing the plan, design, operation, and maintenance of the water resource projects for hydraulic engineers, and since the worth of this value has a significant effect on the analysis of the water level and flow rate distribution, it is very important to carry out the calculation of flood stage, design of the stream/river structure, and safety assessment of the stream. Due to the importance of these factors, the calculation of objective and quantitative roughness coefficient has long drawn attention from researchers at home and abroad. Many studies have been conducted to estimate the roughness coefficient based on the actual measurements for various types of streams, such as gravel and sand streams, and many others have produced experience equation for various levels of materials and relative depth. Despite many of these efforts, the roughness coefficient uses constant values when applied to the actual model or real design. This application is a major source of error in simulating flood and unsteady flow. To solve these problems, good results were obtained by attempting to calculate the roughness coefficient applied with the entropy concept in open-channel flow. In particular, the proposed roughness coefficient based on the measurements taken from laboratories under conditions showed very similar to the actual stream flow which was found to be about the same as the value from the unsteady flow. Accordingly, the newly developed roughness coefficient equation, which is the result of this study, is a very practical one formula that can be applied to the flood flow of real natural streams. It can also be used as an alternative to make up for the disadvantages of the Manning’s roughness coefficient.