Examples of the palladium‐catalyzed coupling of organotin compounds with carbon electrophiles were first reported in 1977 by Kosugi, Shimizu, and Migita. The first study by Stille appeared in 1978. The early work of Beletskaya, using “ligandless” catalysts in cross‐coupling reactions, also often employed organostannanes. In recognition of Stille's comprehensive synthetic and mechanistic studies, this coupling is now referred to as the Stille reaction. R 1 is typically an unsaturated moiety (e.g., vinyl, aryl, heteroaryl, alkynyl, allyl) or less often an alkyl group, and R 2 , the nontransferable ligand, is almost always butyl or methyl. Electrophiles participating in the coupling include halides (almost always bromides or iodides) and sulfonates (most often used are the triflates). Other leaving groups have been used in special cases. The Stille reaction belongs to the larger family of palladium‐ and nickel‐catalyzed cross‐coupling reactions which features, e.g., organomagnesium, organozinc, organoboron, and organosilicon reagents. Organotin reagents are air‐ and moisture‐stable organometallics, and can be conveniently purified and stored. Since they do not react with most common functional groups, the use of protecting groups is almost always unnecessary in conjunction with the Stille reaction. This is a very unusual and attractive feature for an organometallic process. Also, the reaction is often neither air nor moisture sensitive. In some cases, water and oxygen have actually been shown to promote the coupling. Although the reaction as initially described by Stille is often carried out under rather drastic conditions (temperatures of ≥100° are not uncommon), newly developed ligand 11 and the addition of copper(I) salts have solved some of the problems associated with low reactivity. The utility and mildness of the Stille reaction are demonstrated by its frequent use in the final stages of complex natural product syntheses. This chapter attempts a critical and comprehensive coverage of the reaction scope. Mechanistic description of the reaction is rather brief, and the reader is referred to the pertinent literature for a more detailed analysis. All of the relevant literature is covered up to the end of 1994. The reaction was reviewed by Stille in 1986, and by Mitchell in 1992; a rather comprehensive account by Farina and Roth has appeared more recently. Developments that occurred in 1995, as this work was in progress, and that were deemed important were incorporated as much as possible in this review.

A broad‐scale circulation index representing the interannual variability of the Indian summer monsoon is proposed and is shown to be well correlated with the interannual variability of precipitation in the Indian monsoon region. Using monthly precipitation analysis based on merging rain‐gauge data with satellite estimates of precipitation for the period 1979‐96, it is shown that the variability of precipitation on seasonal to interannual time‐scales is coherent over a large region covering the Indian continent as well as the north Bay of Bengal and parts of south China. A new index, termed Extended Indian Monsoon Rainfall (EIMR), is defined as the precipitation averaged over the region 70°E–110°E, 10°N–30°N. the EIMR index is expected to represent the convective heating fluctuations associated with the Indian monsoon better than the traditional all India Monsoon Rainfall (IMR) based only on the precipitation over the Indian continent. It is shown that large precipitation over the Bay of Bengal with significant interannual variability cannot be ignored in the definition of Indian summer monsoon and its variability. the June‐to‐September climatological mean EIMR is found to be larger than that of the IMR even though the former is averaged over a larger area. the dominant mode of interannual variability of the Indian summer monsoon is associated with a dipole between the EIMR region and the north‐western Pacific region (110°E–160°E, 10°N–30°N) and a meridional dipole between the EIMR region and the equatorial Indian Ocean (70°E–110°E, 10°S–5°N). It is argued that the interannual variability of the monsoon circulation is primarily driven by gradients of diabatic heating associated with variations of the EIMR, and that the regional monsoon Hadley circulation is a manifestation of this heating. an index of the monsoon Hadley (MH) circulation is defined as the meridional wind‐shear anomaly (between 850 hPa and 200 hPa) averaged over the same domain as the EIMR, Using circulation data from two independent reanalysis products, namely the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis and the European Centre for Medium‐Range Weather Forecasts reanalysis, it is shown that the MH index is significantly correlated with the EIMR. Also it is shown that both the EIMR and MH indices have a dominant quasi‐biennial variability, consistent with previous studies of IMR. Teleconnections of IMR, EIMR and MH indices with summer sea surface temperature (SST) have also been investigated. There are indications that the south equatorial Indian Ocean SST has a strong positive correlation with the EIMR. Also it is noted that the correlation of the monsoon indices with the eastern Pacific SST was weak during the period under consideration primarily due to almost a reverse relationship between monsoon and El Niño and Southern Oscillation during the latest eight years.

Empirical evidence is presented to support a hypothesis that the interdecadal variation of the Indian summer monsoon and that of the tropical SST are parts of a tropical coupled ocean-atmosphere mode. The interdecadal variation of the Indian monsoon rainfall (IMR) is strongly correlated with the interdecadal variations of various indices of El Niño-Southern Oscillation (ENSO). It is also shown that the interannual variances of both IMR and ENSO indices vary in phase and follow a common interdecadal variation. However, the correlation between IMR and eastern Pacific SST or between IMR and Southern Oscillation index (SOI) on the interannual timescale does not follow the interdecadal oscillation. The spatial patterns of SST and sea level pressure (SLP) associated with the interdecadal variation of IMR are nearly identical to those associated with the interdecadal variations of ENSO indices. As has been shown earlier in the case of ENSO, the global patterns associated with the interdecadal and interannual variability of the Indian monsoon are quite similar. The physical link through which ENSO is related to decreased monsoon rainfall on both interannual and interdecadal timescales has been investigated using National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis products. The decrease in the Indian monsoon rainfall associated with the warm phases of ENSO is due to an anomalous regional Hadley circulation with descending motion over the Indian continent and ascending motion near the equator sustained by the ascending phase of the anomalous Walker circulation in the equatorial Indian Ocean. It is shown that, to a large extent, both the regional Hadley circulation anomalies and Walker circulation anomalies over the monsoon region associated with the strong (weak) phases of the interdecadal oscillation are similar to those associated with the strong (weak) phases of the interannual variability. However, within a particular phase of the interdecadal oscillation, there are several strong and weak phases of the interannual variation. During a warm eastern Pacific phase of the interdecadal variation, the regional Hadley circulation associated with El Niño reinforces the prevailing anomalous interdecadal Hadley circulation while that associated with La Niña opposes the prevailing interdecadal Hadley circulation. During the warm phase of the interdecadal oscillation, El Niño events are expected to be strongly related to monsoon droughts while La Niña events may not have significant relation. On the other hand, during the cold eastern Pacific phase of the interdecadal SST oscillation, La Niña events are more likely to be strongly related to monsoon floods while El Niño events are unlikely to have a significant relation with the Indian monsoon. This picture explains the observation that the correlations between IMR and ENSO indices on the interannual timescale do not follow the interdecadal oscillation as neither phase of the interdecadal oscillation favors a stronger (or weaker) correl...

A gridded daily rainfall dataset prepared from observations at 3700 stations is used to analyze the intraseasonal and interannual variability of the summer monsoon rainfall over India. It is found that the major drought years are characterized by large-scale negative rainfall anomalies covering nearly all of India and persisting for the entire monsoon season. The intraseasonal variability of rainfall during a monsoon season is characterized by the occurrence of active and break phases. During the active phase, the rainfall is above normal over central India and below normal over northern India (foothills of the Himalaya) and southern India. This pattern is reversed during the break phase. It is found that the nature of the intraseasonal variability is not different during the years of major droughts or major floods. This suggests that a simple conceptual model to explain the interannual variability of the Indian monsoon rainfall should consist of a linear combination of a large-scale persistent seasonal mean component and a statistical average of intraseasonal variations. The large-scale persistent component can be part of lowfrequency components of the coupled ocean-land-atmosphere system including influences of sea surface temperature, snow, etc. The mechanisms responsible for the intraseasonal variations are not well understood. This simple conceptual framework suggests that the ability to predict the seasonal mean rainfall over India will depend on the relative contributions of the externally forced component and the intraseasonal component. To the extent that the intraseasonal component is intrinsically unpredictable, success in long-range forecasting will largely depend on accurate quantitative estimates of the externally forced component.

Recent progress in acquiring shape from range data permits the acquisition of seamless million-polygon meshes from physical models. In this paper, we present an algorithm and system for converting dense irregular polygon meshes of arbitrary topology into tensor product B-spline surface patches with accompanying displacement maps. This choice of representation yields a coarse but efficient model suitable for animation and a fine but more expensive model suitable for rendering.The first step in our process consists of interactively painting patch boundaries over a rendering of the mesh. In many applications, interactive placement of patch boundaries is considered part of the creative process and is not amenable to automation. The next step is gridded resampling of each bounded section of the mesh. Our resampling algorithm lays a grid of springs across the polygon mesh, then iterates between relaxing this grid and subdividing it. This grid provides a parameterization for the mesh section, which is initially unparameterized. Finally, we fit a tensor product B-spline surface to the grid. We also output a displacement map for each mesh section, which represents the error between our fitted surface and the spring grid. These displacement maps are images; hence this representation facilitates the use of image processing operators for manipulating the geometric detail of an object. They are also compatible with modern photo-realistic rendering systems.Our resampling and fitting steps are fast enough to surface a million polygon mesh in under 10 minutes -important for an interactive system.

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The tropical disturbances formed in the Bay of Bengal and the Arabian Sea and over land points in central India, known as low pressure systems (LPSs), are shown to contribute significantly to the seasonal monsoon rainfall over India. Analyses of daily rainfall over India and statistics of the LPSs for the period of show that the rainfall pattern when the LPSs are present captures the most dominant daily rainfall pattern that represents the active monsoon phase. The rainfall pattern when the LPSs are absent is similar to the pattern representing the break monsoon phase. The location, number, and duration of the LPSs are found to be closely related to the phases and propagation of the dominant intraseasonal modes of the Indian rainfall. The LPSs are also associated with the strengthening of the monsoon trough and low-level monsoon winds. The number of LPSs and their total duration and the corresponding rainfall during July and August exceed those in June and September. The LPS tracks reach up to northwest India during flood years, whereas they are confined to central India during drought years. However, the contribution of rainfall during the LPSs to the total seasonal rainfall is same during flood or drought years. Although the LPSs seem to play an important role in the monsoon rainfall, they alone may not determine the interannual variability of the seasonal mean monsoon rainfall.

The space–time structure of the active and break periods of the Indian monsoon has been studied using 70-yr-long high-resolution gridded daily rainfall data over India. The analysis of lagged composites of rainfall anomalies based on an objective categorization of active and break phases shows that the active (break) cycle, with an average life of 16 days, starts with positive (negative) rainfall anomalies over the Western Ghats and eastern part of central India and intensifies and expands to a region covering central India and parts of north India during the peak phase, while negative (positive) anomalies cover the sub-Himalayan region and southeast India. During the final stage of the active (break) period, the positive (negative) rainfall anomalies move toward the foothills of the Himalayas while peninsular India is covered with opposite sign anomalies. The number of days on which lows and depressions are present in the region during active and break periods is consistent with the rainfall analysis. The number of depressions during the active phase is about 7 times that during the break phase. Using multichannel singular spectrum analysis of the daily rainfall anomalies, the seasonal monsoon rainfall is found to consist of two dominant intraseasonal oscillations with periods of 45 and 20 days and three seasonally persisting components. The 45- and 20-day oscillations are manifestations of the active and break periods but contribute very little to the seasonal mean rainfall. The seasonally persisting components with anomalies of the same sign, and covering all of India, have a very high interannual correlation with the total seasonal mean rainfall. These results support a conceptual model of the interannual variability of the monsoon rainfall consisting of seasonal mean components and a statistical average of the intraseasonal variations. The success in the prediction of seasonal mean rainfall depends on the relative strengths of the seasonally persisting components and intraseasonal oscillations.