Abstract Whether annual evapotranspiration of native ecosystems is increasing or decreasing with time as CO 2 concentrations are rising, the climate is warming and rainfall experiences booms and busts, remains an unanswered question in the field of global change biology. To answer this question, we measured evapotranspiration and carbon dioxide exchange over and under an oak savanna and over an annual grassland in the Mediterranean climate of California, USA, from 2001 through 2019 with the eddy covariance method; during this 19‐year period, CO 2 rose 40 ppm, air temperature increased by 1°C and annual rainfall ranged between 133 and 890 mm/year. No temporal trend in evapotranspiration or water use efficiency was observed over this time duration. Many competing positive and negative feedbacks among stomatal sensitivity to carbon dioxide concentrations, soil moisture, and vapor pressure deficit, the impact of temperature on saturation vapor pressure and access to groundwater muted the response of evapotranspiration to its changing world when integrated to the ecosystem scale and annual time steps. At the intra‐annual time scale, we found that plants transmit information on soil moisture status through their influence on the vapor pressure deficit of the atmospheric boundary layer. The inter‐annual variations in evaporative water use by the savanna and annual grassland were relatively decoupled from the booms and busts in rainfall. Instead, variations in length of growing season and access to groundwater explained much of this year‐to‐year variation in annual evapotranspiration. The access of groundwater by the oak savanna may make these ecosystems more robust in a warmer world, than was previously thought. This is a scale emergent property that needs better consideration in coupled climate‐ecosystem models.
A strictly two-coordinate nickel(II) bis(amido) complex has been prepared and its reactivity towards a variety of small molecules is described. Ni[N(SiMe(3))(DIPP)](2) reacts with DMAP and acetonitrile to form T-shaped three-coordinate complexes, and preliminary results show that Ni[N(SiMe(3))(DIPP)](2) is a catalyst for the hydrosilation of olefins with secondary silanes at ambient temperature.
A non-equilibrium theory of isothermal and diffusionless evolution of incoherent interfaces within a plastically deforming solid is developed. The irreversible dynamics of the interface are driven by its normal motion, incoherency (slip and misorientation), and an intrinsic plastic flow; and purely by plastic deformation in the bulk away from the interface. Using the continuum theory for defect distribution (in bulk and over the interface) we formulate a general kinematical framework, derive relevant balance laws and jump conditions, and prescribe a thermodynamically consistent constitutive/kinetic structure for interface evolution.
The foundational aspects of an important subclass of timeinvariant nonlinear <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</tex> -ports are dealt with; namely, the class of algebraic <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</tex> -ports that includes, among other things, resistors, inductors, capacitors, and memristors as special cases. Sufficient conditions that guarantee an algebraic <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</tex> -port to admit all <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2^n</tex> hybrid representations are given. Both global and local characterizations are considered in detail. In particular, certain global properties are shown to be invariants relative to the various modes of hybrid representation. The concept of reciprocity is explored in depth and shown to play an important role in determining such global properties as losslessness and passivity. Several generalized potential functions are defined for reciprocal algebraic <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</tex> -ports. These functions are then used to derive a number of interesting circuit theoretic properties for nonlinear <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</tex> -ports.
Major worldwide demographic trends impact significantly each aspect of people’s lives. The impact will be favorable for some states and completely unfavorable for others since they will depend not only on the magnitude of these tendencies, but also on the aggregated result of the inherent shifts and developments at political, economic, social and military level Global demographic trends will represent a genuine challenge for the powerful states to maintain the existing global political and economic equilibrium and they will also constitute a genuine shocking force for international security and stability. At the same time, they will represent one of the variables underpinning states’ strategies, and domestic and foreign policies and influencing political and military alliances in the future. It is likely that they will lead to the reassessment of the bases of international relations. This paper analyzes the presumed consequences of future demographic shifts on the economic, political, military field and proposes some possible solutions to efficiently manage the issue.
We present spectroscopic and extensive photometric observations of supernova (SN) 1998de in the S0 galaxy NGC 252, discovered during the course of the Lick Observatory Supernova Search. These data, which span a time period of 8 days before to 76 days after $B$-band maximum, unambigously establish SN 1998de as a peculiar and subluminous SN Ia with strong similarities to SN 1991bg, the prototype of these intrinsically dim SNe Ia. We find that subluminous SNe Ia with the same Delta m_{15}(B) can have slightly different light curves at longer wavelengths. The notable spectroscopic similarities between SN 1998de and SN 1991bg are the wide Ti II trough at 4100-4500 A, the strong Ca II features, and the early onset of the nebular phase. We observe that spectroscopic deviations of SN 1998de from SN 1991bg increase toward redder wavelenghts. These deviations include the absence of the conspicuous Na I D absorption found in SN 1991 at 5700 A, and the evolution of a region (6800-7600 A) from featureless to feature-rich. Several lines of evidence suggest that SN 1998de was a slightly more powerful explosion than SN 1991bg. We discuss the implications of our observations for progenitor models and the explosion mechanism of peculiar, subluminous SNe Ia. The extensive photometric data make SN 1998de a better template than SN 1991bg for calibrating the low-luminosity end of the luminosity vs. decline-rate relationship.
We experience the world around us as “continuous,” which means everything around us seems uninterrupted and ongoing. But how does our brain achieve that? Here, we suggest that the brain samples our environment in separate snapshots. We demonstrate that brain waves work just like a flipbook, where the rapid stream of related pictures creates the illusion of a continuous movie. We present results from a recent experiment that shows how brain waves capture the world that we see. These brain waves occur approximately 10 times per second and are called “alpha oscillations.” Here, we provide an overview of how these brain waves were discovered, how they can be measured, what they mean, and how they help to create our perception of the world around us.
