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There is a long history of exploitation of the South American river turtle Podocnemis expansa. Conservation efforts for this species started in the 1960s but best practices were not established, and population trends and the number of nesting females protected remained unknown. In 2014 we formed a working group to discuss conservation strategies and to compile population data across the species’ range. We analysed the spatial pattern of its abundance in relation to human and natural factors using multiple regression analyses. We found that > 85 conservation programmes are protecting 147,000 nesting females, primarily in Brazil. The top six sites harbour > 100,000 females and should be prioritized for conservation action. Abundance declines with latitude and we found no evidence of human pressure on current turtle abundance patterns. It is presently not possible to estimate the global population trend because the species is not monitored continuously across the Amazon basin. The number of females is increasing at some localities and decreasing at others. However, the current size of the protected population is well below the historical population size estimated from past levels of human consumption, which demonstrates the need for concerted global conservation action. The data and management recommendations compiled here provide the basis for a regional monitoring programme among South American countries.
Quantifying the physical mechanisms responsible for the transport of sediments, nutrients and pollutants in the abyssal sea is a long-standing problem, with internal waves regularly invoked as the relevant mechanism for particle advection near the sea bottom. This study focuses on internal-wave-induced particle transport in the vicinity of (almost) vertical walls. We report a series of laboratory experiments revealing that particles sinking slowly through a monochromatic internal wave beam experience significant horizontal advection. Extending the theoretical analysis by Beckebanze et al. (J. Fluid Mech., vol. 841, 2018, pp. 614–635), we attribute the observed particle advection to a peculiar and previously unrecognized streaming mechanism in the stratified boundary layer originating at the lateral walls. This vertical boundary layer streaming mechanism is most efficient for significantly inclined wave beams, when vertical and horizontal velocity components are of comparable magnitude. We find good agreement between our theoretical prediction and experimental results.
We present a continuous, sediment core-based record of paleohydroclimate spanning ~5800 cal yr BP to recent from Lower Pahranagat Lake (LPAH), a shallow, alkaline lake in southern Nevada. We apply stable isotopes (δ18O and δ13C) from fine-fraction authigenic carbonate, which are sensitive recorders of hydroclimatic variability in this highly evaporative region. Additional geochemical proxies (total organic carbon, C/N, and total inorganic carbon) provide supporting information on paleoecological change in and around the lake. Our data suggest progressively wetter conditions starting at the later part of the middle Holocene and extending into the late Holocene (~5500–3350 cal yr BP) followed by a millennial-scale dry period from ~3150 to 1700 cal yr BP. This latter interval encompasses the ‘Late Holocene dry period’ (LHDP) reported by other investigators, and our data help refine the area affected in this episode. Our data also show evidence for a series of century-scale fluctuations in regional hydroclimate, including wet and dry intervals between 2350 and 1600 cal yr BP, and drier conditions over the past few centuries. Paleohydroclimate trends in the LPAH record show correspondence with those from the central Great Basin to the north, suggesting that both areas were subject to similar climatic forcings.
As of 2015, the percentage of the unemployed who are long-term unemployed remains at levels unseen in the US in over six decades. A well-established literature associates long-term unemployment with a variety of social ills, including poverty, increased risk of physical and mental health problems, and deteriorating emotional well-being. This chapter describes the nature and scope of long-term unemployment in the United States and its impact on individuals and families. It also focuses on the issue of mental health and explores the causal relationship between long-term unemployment and mental health as well as the most promising solutions to the mental health challenges raised by long-term unemployment. The final section of the chapter focuses on the challenges that arise when long-term unemployed workers internalize the stigma of unemployment and blame themselves for their labor market difficulties, and it considers possible causes of and solutions to such self-blame.
Older care home residents are excluded from the sexual imaginary. Based on a consultative study involving interviews with three residents, three female spouses of residents and two focus groups of care home staff (N = 16), making an overall sample of 22 study participants, we address the neglected subject of older residents' sexuality and intimacy needs. Using thematic analysis, we highlight how residents’ and spouses’ accounts of sexuality and intimacy can reflect an ageist erotophobia occurring within conditions of panoptical control that help construct residents as post-sexual. However, not all accounts contributed to making older residents’ sexuality appear invisible or pathological. Some stories indicated recuperation of identities and the normalisation of relationships with radically changed individuals, e.g. because of a dementia. We also examine care home staff accounts of the discursive obstacles that frustrate meeting residents’ needs connected with sexuality and intimacy. Simultaneously, we explore staffs’ creative responses to dilemmas which indicate approaches to sexuality driven more by observed needs than erotophobic anxiety and governance, as well as panoptical surveillance.
In traditional electron/ion laboratory plasmas, the system size
is much larger than both the plasma skin depth
and the Debye length
. In current and planned efforts to create electron/positron plasmas in the laboratory, this is not necessarily the case. A low-temperature, low-density system may have
; a high-density, thermally relativistic system may have
. Here we consider the question of what plasma physics phenomena are accessible (and/or diagnostically exploitable) in these different regimes and how this depends on magnetization. While particularly relevant to ongoing pair plasma creation experiments, the transition from single-particle behaviour to collective, ‘plasma’ effects – and how the criterion for that threshold is different for different phenomena – is an important but often neglected topic in electron/ion systems as well.
Depression is a significant problem and it is vital to understand its underlying causes and related policy implications. Neighborhood characteristics are implicated in depression but the nature of this association is unclear. Unobserved or unmeasured factors may confound the relationship. This study addresses confounding in a twin study investigating neighborhood-level effects on depression controlling for genetics, common environment, and gene×environment (G × E) interactions.
Data on neighborhood deprivation and depression were gathered from 3155 monozygotic twin pairs and 1275 dizygotic pairs (65.7% female) between 2006 and 2013. The variance for both depression and neighborhood deprivation was decomposed into three components: additive genetic variance (A); shared environmental variance (C); and non-shared environmental variance (E). Depression was then regressed on neighborhood deprivation to test the direct association and whether that association was confounded. We also tested for a G × E interaction in which the heritability of depression was modified by the level of neighborhood deprivation.
Depression and neighborhood deprivation showed evidence of significant A (21.8% and 15.9%, respectively) and C (13.9% and 32.7%, respectively) variance. Depression increased with increasing neighborhood deprivation across all twins (p = 0.009), but this regression was not significant after controlling for A and C variance common to both phenotypes (p = 0.615). The G × E model showed genetic influences on depression increasing with increasing neighborhood deprivation (p < 0.001).
Neighborhood deprivation is an important contributor to depression via increasing the genetic risk. Modifiable pathways that link neighborhoods to depression have been proposed and should serve as targets for intervention and research.
Chamorro-Premuzic, Winsborough, Sherman, and Hogan (2016) note that new talent signals recently adopted by organizations are related to older selection and assessment methods. Drawing this connection between old and new technologies is helpful; however, viewing new technology as either shiny new objects or a brave new world creates a false dichotomy. Recent technology-enhanced human resources (HR) processes like the widespread use of gamified practices and video-recorded interviewing are not just fads or the beginning of a transformation in HR but rather natural evolutions of methods that differ across specific dimensions that can be identified and measured. It is important to view these recent advances as extensions of the existing methods. That is, we need to focus on how these new methods are different and not on that they are different.
Sexuality and intimacy in care homes for older people are overshadowed by concern with prolonging physical and/or psychological autonomy. When sexuality and intimacy have been addressed in scholarship, this can reflect a sexological focus concerned with how to continue sexual activity with reduced capacity. We review the (Anglophone) academic and practitioner literatures bearing on sexuality and intimacy in relation to older care home residents (though much of this applies to older people generally). We highlight how ageism (or ageist erotophobia), which defines older people as post-sexual, restricts opportunities for the expression of sexuality and intimacy. In doing so, we draw attention to more critical writing that recognises constraints on sexuality and intimacy and indicates solutions to some of the problems identified. We also highlight problems faced by lesbian, gay, bisexual and trans (LGB&T) residents who are doubly excluded from sexual/intimate citizenship because of ageism combined with the heterosexual assumption. Older LGB&T residents/individuals can feel obliged to deny or disguise their identity. We conclude by outlining an agenda for research based on more sociologically informed practitioner-led work.
Ca supplements are used for bone health; however, they have been associated with increased cardiovascular risk, which may relate to their acute effects on serum Ca concentrations. Microcrystalline hydroxyapatite (MCH) could affect serum Ca concentrations less than conventional Ca supplements, but its effects on bone turnover are unclear. In the present study, we compared the acute and 3-month effects of MCH with conventional Ca supplements on concentrations of serum Ca, phosphate, parathyroid hormone and bone turnover markers. We randomised 100 women (mean age 71 years) to 1 g/d of Ca as citrate or carbonate (citrate–carbonate), one of two MCH preparations, or a placebo. Blood was sampled for 8 h after the first dose, and after 3 months of daily supplementation. To determine whether the acute effects changed over time, eight participants assigned to the citrate dose repeated 8 h of blood sampling at 3 months. There were no differences between the citrate and carbonate groups, or between the two MCH groups, so their results were pooled. The citrate–carbonate dose increased ionised and total Ca concentrations for up to 8 h, and this was not diminished after 3 months. MCH increased ionised Ca concentrations less than the citrate–carbonate dose; however, it raised the concentrations of phosphate and the Ca–phosphate product. The citrate–carbonate and MCH doses produced comparable decreases in bone resorption (measured as serum C-telopeptide (CTX)) over 8 h and bone turnover (CTX and procollagen type-I N-terminal propeptide) at 3 months. These findings suggest that Ca preparations, in general, produce repeated sustained increases in serum Ca concentrations after ingestion of each dose and that Ca supplements with smaller effects on serum Ca concentrations may have equivalent efficacy in suppressing bone turnover.
Imidazoles present a tunable, versatile and economical platform for the development of novel liquid solvents and polymer membranes for CO2 capture. An overview of our studies in this area is presented, with emphasis on characterization of structure-property relationships in imidazole-based materials through both experimental and computational studies. To this end, a growing library of systematically varied imidazole compounds has been synthesized using only commercial available starting materials and straightforward reactions. Using this library of compounds, we have sought to understand and develop predictive models for thermophysical properties relating to process design, including: density, viscosity, vapor pressure, pKa and CO2 absorption capacity. Furthermore, we have discovered that imidazoles are stable in the presence of SO2 and can form reversible 1:1 adducts, which can be beneficial as SO2 is typically present at ppm levels alongside CO2 in flue gas from coal-fired power plants.
The need for a rigorous, yet practical, framework for characterization, modeling, and design of nonlinear electronic components at high frequencies has never been more urgent. The communications revolution is inexorably forcing active devices into more and more strongly nonlinear regimes of operation. This is a consequence of the relentless drive for more efficiency in order to save power, extend battery life, and minimize cooling. The price for efficiency is nonlinearity. Dealing with nonlinearity means that new measurement instrumentation and new modeling and design methodologies are required that go far beyond linear S-parameters. Fortunately, there is an overarching, interoperable paradigm combining all these pieces of the nonlinear puzzle together, seamlessly. The new paradigm is called X-parameters, and that is what this book is about.
The book is intended as a comprehensive introduction to X-parameters. It is aimed at a diverse audience with a wide range of backgrounds. This is quite a challenging undertaking! We are targeting professional microwave engineers, device modeling engineers and scientists, RF and microwave circuit designers, electronic and communications engineers, CAE professionals developing simulator algorithms, and microwave and RF professionals developing new high-speed instrumentation for a wide range of nonlinear characterization applications. The inherent interdisciplinary nature of X-parameters is the prime reason we seek to appeal to this broad audience. The practical solutions based on X-parameters deployed by industry over the past several years depend on contributions in all of these areas.
One of the key features that led to the wide adoption of S-parameters was the availability of hardware and calibration techniques capable of making quick, accurate, and repeatable S-parameter measurements. S-parameters can also be easily extracted in simulation from device or circuit models. In either case, the resulting S-parameters can immediately be used in simulation or design tools. In order to achieve similar success in the nonlinear domain, X-parameters must be easily measured and also easily extracted from simulation.
X-parameters, like S-parameters, represent the steady-state behavior of a device in the frequency domain. The linearity assumption of S-parameters, however, greatly simplifies the measurement requirements. The additional capabilities of X-parameters come at the cost of additional complexity in the measurement system as well as the modeling paradigm.
X-parameters include cross-frequency terms that capture the distortion products generated
by device nonlinearities. In order to measure these terms, the measurement
hardware must be capable of measuring coherent cross-frequency phase. Because
S-parameters include no cross-frequency interaction (a consequence of the linearity
assumption), each frequency may be measured independently with no need for a
consistent time base or cross-frequency phase. Since all S-parameters are ratios of
waves, there is also no need for accurate measurement of absolute power – only the
relative power is needed. As a result, the hardware and calibration techniques developed
for S-parameter measurement generally are not sufficient for X-parameter measurement
and must be extended to include cross-frequency phase and calibrated absolute power.
This chapter presents a concise treatment of S-parameters, meant primarily as an introduction to the more general formalism of X-parameters. The concepts of time invariance and spectral maps are introduced at this stage to enable an easier generalization to X-parameters in the ensuing chapters. The interpretations of S-parameters as calibrated measurements, intrinsic properties of the device under test (DUT), IP-secure component behavioral models, and composition rules for linear system design are presented. The cascade of two linear S-parameter components is considered as an example to be generalized to the nonlinear case later. The calculation of S-parameters for a transistor from a simple nonlinear device model is used as an example to introduce the concepts of (static) operating point and small-signal conditions, both of which must be generalized for the treatment of X-parameters.
Since the 1950s, S-parameters, or scattering parameters, have been among the most important of all the foundations of microwave theory and techniques.
S-parameters are easy to measure at high frequencies with a vector network analyzer
(VNA). Well-calibrated S-parameter measurements represent intrinsic properties of the
DUT, independent of the VNA system used to characterize it. Calibration procedures 
remove systematic measurement errors and enable a separation of the overall values into
numbers attributable to the device, independent of the measurement system used to
characterize it. These DUT properties (gain, loss, reflection coefficient, etc.) are familiar,
intuitive, and important . Another key property of S-parameters is that the
S-parameters of a composite system are completely determined from knowledge of
the S-parameters of the constituent components and their connectivity. S-parameters
provide the complete specification of how a linear component responds to an arbitrary
signal. Therefore designs of linear systems with S-parameters are predictable with
absolute certainty. S-parameters define a complete behavioral description of the linear
component at the external terminals, independent of the detailed physics or specifics of
the realization of the component. S-parameters can be shared between component
vendors and system integrators freely, without the possibility that the component implementation can be reverse engineered, protecting IP and promoting sharing and
reuse. Indeed, one may ask the question, “are S-parameters measurements, or do they
constitute a model?” The answer is really “both.”
This is the definitive guide to X-parameters, written by the original inventors and developers of this powerful new paradigm for nonlinear RF and microwave components and systems. Learn how to use X-parameters to overcome intricate problems in nonlinear RF and microwave engineering. The general theory behind X-parameters is carefully and intuitively introduced, and then simplified down to specific, practical cases, providing you with useful approximations that will greatly reduce the complexity of measuring, modeling and designing for nonlinear regimes of operation. Containing real-world case studies, definitions of standard symbols and notation, detailed derivations within the appendices, and exercises with solutions, this is the definitive stand-alone reference for researchers, engineers, scientists and students looking to remain on the cutting-edge of RF and microwave engineering.