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"Leon, P"
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Political ideologies : their origins and impact
\"Comprehensive yet accessible, this classic text, now in its thirteenth edition follows the evolution of political thought over 300 years. Organized chronologically, this text examines each ideology within a political, historical, economic, and social context. In addition to a thorough updating of examples and data, here's what you'll find in the new edition: Analyses of President Trump's rollback of Obamacare, trade war with China, and changes to immigration, taxation and environmental policy. Conservative justifications for supply-side economics and liberal rationale for drug legalization and \"trigger-word\" bans. Brexit's effects on the Scottish independence movement. Resurgence of feminist protest, including the MeToo movement, alongside anarchist protest, following Trump's election, including groups like Black Bloc and Antifa. China's rising environmental and social problems, including unrest among its heavily controlled Uighur population. Cuba's transfer of power from the Castros to President Dâiaz-Canel, and their fraught rapprochement with the U.S. Russia's disinformation campaigns, and alternating brinksmanship and dâetente between Trump and North Korea's Chairman Kim Jong-un. The ascent of the Alt-right in the US, and white supremacist influence on parties in the U.S. and Europe. The continuing salience of Islamism, the teetering Iran deal, and ongoing degeneration of the Arab Spring to the Islamist Winter\"-- Provided by publisher.
Book
Salinization of coastal freshwater wetlands; effects of constant versus fluctuating salinity on sediment biogeochemistry
Globally, coastal lowlands are becoming more saline by the combined effects of sea level rise, land subsidence and altered hydrological and climatic conditions. Although salinization is known to have a great influence on biogeochemical processes, literature shows contrasting effects that challenge the prediction of future effects. In addition, the effects of fluctuating salinity levels, a more realistic scenario than constant levels, on nutrient cycling in coastal wetland sediments have hardly been examined. A better understanding is therefore crucial for the prediction of future effects and the definition of effective management. To test the effects of constantly brackish water (50 mmol Cl l⁻¹, 3.2 psu) or fluctuating salinity (5–50 mmol Cl l⁻¹), versus constantly low salinity (5 mmol Cl l⁻¹, 0.32 psu) on nutrient biogeochemistry, we conducted a controlled laboratory experiment with either peat or clay sediments from coastal wetlands. Increased salinity showed to have a fast and large effect. Sediment cation exchange appeared to be the key process explaining both a decrease in phosphorus availability (through calcium mobilization) and an increase in nitrogen availability, their extent being strongly dependent on sediment type. Supply of brackish water decreased surface water turbidity and inhibited sediment methane production but did not affect CO₂ production. Constant and fluctuating salinity levels showed similar longer term effects on nutrient and carbon cycling. The contrasting effects of salinization found for nitrogen and phosphorus, and its effects on water turbidity indicate major ecological consequences for coastal wetlands and have important implications for water management and nature restoration.
Journal Article
علم الأحياء والأيديولوجيا والطبيعة البشرية
ينبري مؤلفو هذا الكتاب لبعض المزاعم منها : \"زعم البعض أن من الأعراق أو الأجناس ما هو أحط من غيرها، مع محاولة إثبات أن هذا له دليل علمي يرجع إلى التكوين الوراثي الذي تحمله الجينات، مما لا يقبل التغيير\" فيفندونها في دحض كامل لنظرية الحتمية البيولوجية وما تدعيه من تعريفها لطبيعة الإنسان المحتومة وراثيا، ويتم ذلك من خلال دراسة نقدية علمية مسهبة وشيقة عن طبيعة الوراثة والبيئة في عدة موضوعات مهمة من بينها نظرية معامل الذكاء، وما تدعي من وجود فروق أساسية بين الأعراق وبين الجنسين، ومشاكل علاج الأمراض العقلية، وتحويل أصول المشاكل الاجتماعية إلى مسببات طبية وراثية، وغير ذلك من نظريات البيولوجيين الاجتماعيين التي ترد سلوك الإنسان في تبسيط مخل إلى عامل أساسي واحد هو الوراثة. وفي هذا كله يوضح المؤلفون في تحليل علمي متمكن، ومن خلال منظور تاريخي التأثير المتبادل بين الأيديولوجيا والعلم.
Book
Observation of an environmentally insensitive solid-state spin defect in diamond
Certain defects in diamond are among the most promising physical implementations of qubits, the building blocks of quantum computers. However, identifying a defect with balanced properties is tricky: Nitrogen vacancy centers have a long lifetime but comparatively poor optical properties, whereas negatively charged silicon vacancy centers have the opposite characteristics. Rose et al. used careful materials engineering to stabilize the neutral charge state of silicon vacancy centers and found that they combine long coherence times with excellent optical properties. Science , this issue p. 60 The neutral charge state of silicon vacancy centers in diamond shows promising quantum information properties. Engineering coherent systems is a central goal of quantum science. Color centers in diamond are a promising approach, with the potential to combine the coherence of atoms with the scalability of a solid-state platform. We report a color center that shows insensitivity to environmental decoherence caused by phonons and electric field noise: the neutral charge state of silicon vacancy (SiV 0 ). Through careful materials engineering, we achieved >80% conversion of implanted silicon to SiV 0 . SiV 0 exhibits spin-lattice relaxation times approaching 1 minute and coherence times approaching 1 second. Its optical properties are very favorable, with ~90% of its emission into the zero-phonon line and near–transform-limited optical linewidths. These combined properties make SiV 0 a promising defect for quantum network applications.
Journal Article
Analysing the Impact of Artificial Intelligence and Computational Sciences on Student Performance: Systematic Review and Meta-analysis
Artificial intelligence (AI) and computational sciences have aroused a growing interest in education. Despite its relatively recent history, AI is increasingly being introduced into the classroom through different modalities, with the aim of improving student achievement. Thus, the purpose of the research is to analyse, quantitatively and qualitatively, the impact of AI components and computational sciences on student performance. For this purpose, a systematic review and meta-analysis have been carried out in WOS and Scopus databases. After applying the inclusion and exclusion criteria, the sample was set at 25 articles. The results support the positive impact that AI and computational sciences have on student performance, finding a rise in their attitude towards learning and their motivation, especially in the STEM (Science, Technology, Engineering, and Mathematics) areas. Despite the multiple benefits provided, the implementation of these technologies in instructional processes involves a great educational and ethical challenge for teachers in relation to their design and implementation, which requires further analysis from the educational research. These findings are consistent at all educational stages.
Journal Article
Sphagnum Mosses - Masters of Efficient N-Uptake while Avoiding Intoxication
Peat forming Sphagnum mosses are able to prevent the dominance of vascular plants under ombrotrophic conditions by efficiently scavenging atmospherically deposited nitrogen (N). N-uptake kinetics of these mosses are therefore expected to play a key role in differential N availability, plant competition, and carbon sequestration in Sphagnum peatlands. The interacting effects of rain N concentration and exposure time on moss N-uptake rates are, however, poorly understood. We investigated the effects of N-concentration (1, 5, 10, 50, 100, 500 µM), N-form ((15)N-ammonium or nitrate) and exposure time (0.5, 2, 72 h) on uptake kinetics for Sphagnum magellanicum from a pristine bog in Patagonia (Argentina) and from a Dutch bog exposed to decades of N-pollution. Uptake rates for ammonium were higher than for nitrate, and N-binding at adsorption sites was negligible. During the first 0.5 h, N-uptake followed saturation kinetics revealing a high affinity (Km 3.5-6.5 µM). Ammonium was taken up 8 times faster than nitrate, whereas over 72 hours this was only 2 times. Uptake rates decreased drastically with increasing exposure times, which implies that many short-term N-uptake experiments in literature may well have overestimated long-term uptake rates and ecosystem retention. Sphagnum from the polluted site (i.e. long-term N exposure) showed lower uptake rates than mosses from the pristine site, indicating an adaptive response. Sphagnum therefore appears to be highly efficient in using short N pulses (e.g. rainfall in pristine areas). This strategy has important ecological and evolutionary implications: at high N input rates, the risk of N-toxicity seems to be reduced by lower uptake rates of Sphagnum, at the expense of its long-term filter capacity and related competitive advantage over vascular plants. As shown by our conceptual model, interacting effects of N-deposition and climate change (changes in rainfall) will seriously alter the functioning of Sphagnum peatlands.
Journal Article
Spherically symmetric distributions with an invariant and vanishing complexity factor by means of the extended geometric deformation
In this work, we will analyze the complexity factor, proposed by L. Herrera, of spherically symmetric static distribution through the gravitational decoupling method. Specifically, we will consider both spatial and temporal deformations of the metric function, and we will impose conditions over the complexity factor to close the system of equations. In particular, we found that the regularity at the center of both the seed and final solutions led to important restrictions on the deformation of the spatial metric components. These are particularly restrictive for the MGD method. In this case, we show that if the seed solution is regular at
r
=
0
,
the final solution with invariant complexity factor will be singular at this point unless
f
=
0
.
We also show that solutions with the same temporal components will, in general, lead to the same solutions with vanishing complexity factor in the MGD approach. Finally, we will construct realistic models using different seed solutions such as Tolman IV and FS (Finch–Skeas).
Journal Article
New material platform for superconducting transmon qubits with coherence times exceeding 0.3 milliseconds
The superconducting transmon qubit is a leading platform for quantum computing and quantum science. Building large, useful quantum systems based on transmon qubits will require significant improvements in qubit relaxation and coherence times, which are orders of magnitude shorter than limits imposed by bulk properties of the constituent materials. This indicates that relaxation likely originates from uncontrolled surfaces, interfaces, and contaminants. Previous efforts to improve qubit lifetimes have focused primarily on designs that minimize contributions from surfaces. However, significant improvements in the lifetime of two-dimensional transmon qubits have remained elusive for several years. Here, we fabricate two-dimensional transmon qubits that have both lifetimes and coherence times with dynamical decoupling exceeding 0.3 milliseconds by replacing niobium with tantalum in the device. We have observed increased lifetimes for seventeen devices, indicating that these material improvements are robust, paving the way for higher gate fidelities in multi-qubit processors.
Quantum computers based on superconducting transmon qubits are limited by single qubit lifetimes and coherence times, which are orders of magnitude shorter than limits imposed by bulk material properties. Here, the authors fabricate two-dimensional transmon qubits with both lifetimes and coherence times longer than 0.3 milliseconds by replacing niobium with tantalum in the device.
Journal Article
A global perspective on wetland salinization: ecological consequences of a growing threat to freshwater wetlands
Salinization, a widespread threat to the structure and ecological functioning of inland and coastal wetlands, is currently occurring at an unprecedented rate and geographic scale. The causes of salinization are diverse and include alterations to freshwater flows, land-clearance, irrigation, disposal of wastewater effluent, sea level rise, storm surges, and applications of de-icing salts. Climate change and anthropogenic modifications to the hydrologic cycle are expected to further increase the extent and severity of wetland salinization. Salinization alters the fundamental physicochemical nature of the soil-water environment, increasing ionic concentrations and altering chemical equilibria and mineral solubility. Increased concentrations of solutes, especially sulfate, alter the biogeochemical cycling of major elements including carbon, nitrogen, phosphorus, sulfur, iron, and silica. The effects of salinization on wetland biogeochemistry typically include decreased inorganic nitrogen removal (with implications for water quality and climate regulation), decreased carbon storage (with implications for climate regulation and wetland accretion), and increased generation of toxic sulfides (with implications for nutrient cycling and the health/functioning of wetland biota). Indeed, increased salt and sulfide concentrations induce physiological stress in wetland biota and ultimately can result in large shifts in wetland communities and their associated ecosystem functions. The productivity and composition of freshwater species assemblages will be highly altered, and there is a high potential for the disruption of existing interspecific interactions. Although there is a wealth of information on how salinization impacts individual ecosystem components, relatively few studies have addressed the complex and often non-linear feedbacks that determine ecosystem-scale responses or considered how wetland salinization will affect landscape-level processes. Although the salinization of wetlands may be unavoidable in many cases, these systems may also prove to be a fertile testing ground for broader ecological theories including (but not limited to): investigations into alternative stable states and tipping points, trophic cascades, disturbance-recovery processes, and the role of historical events and landscape context in driving community response to disturbance.
Journal Article
Indistinguishable telecom band photons from a single Er ion in the solid state
Atomic defects in the solid state are a key component of quantum repeater networks for long-distance quantum communication
1
. Recently, there has been significant interest in rare earth ions
2
–
4
, in particular Er
3+
for its telecom band optical transition
5
–
7
that allows long-distance transmission in optical fibres. However, the development of repeater nodes based on rare earth ions has been hampered by optical spectral diffusion, precluding indistinguishable single-photon generation. Here, we implant Er
3+
into CaWO
4
, a material that combines a non-polar site symmetry, low decoherence from nuclear spins
8
and is free of background rare earth ions, to realize significantly reduced optical spectral diffusion. For shallow implanted ions coupled to nanophotonic cavities with large Purcell factor, we observe single-scan optical linewidths of 150 kHz and long-term spectral diffusion of 63 kHz, both close to the Purcell-enhanced radiative linewidth of 21 kHz. This enables the observation of Hong–Ou–Mandel interference
9
between successively emitted photons with a visibility of
V
= 80(4)%, measured after a 36 km delay line. We also observe spin relaxation times
T
1,s
= 3.7 s and
T
2,s
> 200 μs, with the latter limited by paramagnetic impurities in the crystal instead of nuclear spins. This represents a notable step towards the construction of telecom band quantum repeater networks with single Er
3+
ions.
Er
3+
is implanted into CaWO
4
, a material with non-polar site symmetry free of background rare earth ions, to realize reduced optical spectral diffusion in nanophotonic devices, representing a step towards making telecom band quantum repeater networks with single ions.
Journal Article