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"Lee, Daniel"
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Human rights and the ethics of globalization
\"Human Rights and the Ethics of Globalization provides a balanced, thoughtful discussion of the globalization of the economy and the ethical considerations inherent in the many changes it has prompted. The book's introduction maps out the philosophical foundations for constructing an ethic of globalization, taking into account both traditional and contemporary sources. These ideals are applied to four specific test cases: the ethics of investing in China, the case study of the Firestone company's presence in Liberia, free-trade and fair-trade issues pertaining to the coffee trade with Ethiopia, and the use low-wage factories in Mexico to serve the U.S. market. The book concludes with a comprehensive discussion of how to enforce global compliance with basic human rights standards, with particular attention to stopping abuses by multinational corporations through litigation under the Alien Tort Claims Act\"--Provided by publisher.
Book
Chromatin mechanics dictates subdiffusion and coarsening dynamics of embedded condensates
DNA is organized into chromatin, a complex polymeric material that stores information and controls gene expression. An emerging mechanism for biological organization, particularly within the crowded nucleus, is biomolecular phase separation into condensed droplets of protein and nucleic acids. However, the way in which chromatin impacts the dynamics of phase separation and condensate formation is poorly understood. Here we utilize a powerful optogenetic strategy to examine the interplay of droplet coarsening with the surrounding viscoelastic chromatin network. We demonstrate that droplet growth dynamics are directly inhibited by the chromatin-dense environment, which gives rise to an anomalously slow coarsening exponent, β ≈ 0.12, contrasting with the classical prediction of β = 1/3. Using scaling arguments and simulations, we show how this arrested growth can arise due to subdiffusion of individual condensates, predicting β ≈ α/3, where α is the diffusive exponent. Tracking the fluctuating motion of condensates within chromatin reveals a subdiffusive exponent, α ≈ 0.5, which explains the anomalous coarsening behaviour and is also consistent with Rouse-like dynamics arising from the entangled chromatin. Our findings have implications for the biophysical regulation of the size and shape of biomolecular condensates and suggest that condensate emulsions can be used to probe the viscoelastic mechanical environment within living cells.Biomolecules in the cell nucleus form condensates at a rate slower than that predicted by the theory of droplet growth. Experiments on living cells attribute this anomalous coarsening behaviour to subdiffusive dynamics in the crowded nucleus.
Journal Article
Separability and geometry of object manifolds in deep neural networks
Stimuli are represented in the brain by the collective population responses of sensory neurons, and an object presented under varying conditions gives rise to a collection of neural population responses called an ‘object manifold’. Changes in the object representation along a hierarchical sensory system are associated with changes in the geometry of those manifolds, and recent theoretical progress connects this geometry with ‘classification capacity’, a quantitative measure of the ability to support object classification. Deep neural networks trained on object classification tasks are a natural testbed for the applicability of this relation. We show how classification capacity improves along the hierarchies of deep neural networks with different architectures. We demonstrate that changes in the geometry of the associated object manifolds underlie this improved capacity, and shed light on the functional roles different levels in the hierarchy play to achieve it, through orchestrated reduction of manifolds’ radius, dimensionality and inter-manifold correlations.
Neural activity space or manifold that represents object information changes across the layers of a deep neural network. Here the authors present a theoretical account of the relationship between the geometry of the manifolds and the classification capacity of the neural networks.
Journal Article
Cell surface crowding is a tunable energetic barrier to cell-cell fusion
Cell-cell fusion is fundamental to processes such as muscle formation and viral infection. An essential step in fusion is close membrane apposition, but cell membranes are crowded with proteins, glycoproteins, and glycolipids, which must be cleared before a fusion pore can be nucleated. Here, we find that cell surface crowding reduces fusogenicity independent of how fusion is driven. We estimate that crowding presents an energetic barrier to membrane apposition on the scale of ~
100
k
B
T
, greater than that of bare membrane fusion alone. We show that increasing cell surface crowding reduces fusion efficiency of PEG-mediated and fusogen-mediated cell-cell fusion, as well as synthetic membranes under force. Interestingly, we find that differentiating myoblasts naturally decrease their surface crowding prior to fusion. In this work, we show that cell surface crowding presents an underappreciated biophysical barrier that may be tuned developmentally and could be targeted externally to control tissue-specific cell-cell fusion.
Cell-cell fusion is fundamental to physiological processes such as muscle formation and viral infection. Here, the authors show that the proteins embedded on the plasma membrane present a biophysical barrier that can regulate cell-cell fusion.
Journal Article
Andalusia : recipes from Seville and beyond
\"Bordering Spain's southern coast, Andalusia is a place where the past and modernity blend together to form a rather magical destination. From sandy beaches to amazing architecture, buzzing tapas bars and flamenco dancers, it's full of passion. Not just a feast for the eyes, Andalusia is also a food-lovers paradise, and Andalusia, award-winning chef José Pizarro takes readers on a journey through it's most delicious dishes. Blessed with land that produces magnificent wild mushrooms, delicious Jabugo ham, and some of the world's best olive oil and seafood, you'll be spoilt for choice. Many of the dishes go back to Moorish times or earlier and each of the eight provinces has their own special dish. Try your hand at Pork loin with pear and hazelnuts, Shrimp baked in salt with mango, chilli, coriander salsa, and a rather boozy Barbary fig margarita. Written in José's signature fuss-free style, this is genuine, bold-tasting Spanish food, easily made at home. Andalusia is all about simple pleasures: a glass of wine or sherry, a piece of cheese or ham, and good company. And that's all you need to make yourself happy. It's all about the freshness, the quality and the diversity of the produce. Set to the backdrop of beautiful location shots, Andalusia is a must for anyone who loves authentic, simple Spanish food.\"--Amazon.com.
Book
A versatile approach for the synthesis of degradable polymers via controlled ring-opening metathesis copolymerization
Norbornene derivatives (NBEs) are common monomers for living ring-opening metathesis polymerization and yield polymers with low dispersities and diverse functionalities. However, the all-carbon backbone of poly-NBEs is non-degradable. Here we report a method to synthesize degradable polymers by copolymerizing 2,3-dihydrofuran with NBEs. 2,3-Dihydrofuran rapidly reacts with Grubbs catalyst to form a thermodynamically stable Ru Fischer carbene—the only detectable active Ru species during copolymerization—and the addition of NBEs becomes rate determining. This reactivity attenuates the NBE homoaddition and allows uniform incorporation of acid-degradable enol ether linkages throughout the copolymers, which enables complete polymer degradation while maintaining the favourable characteristics of living ring-opening metathesis polymerization. Copolymerization of 2,3-dihydrofuran with NBEs gives low dispersity polymers with tunable solubility, glass transition temperature and mechanical properties. These polymers can be fully degraded into small molecule or oligomeric species under mildly acidic conditions. This method can be readily adapted to traditional ring-opening metathesis polymerization of widely used NBEs to synthesize easily degradable polymers with tunable properties for various applications and for environmental sustainability.
Degradable polymers are important for technological applications and sustainability, but they remain difficult to access via ring-opening metathesis polymerization (ROMP). Now, commercial 2,3-dihydrofuran is shown to be an effective ROMP comonomer for various norbornenes. This copolymerization generates new acid-degradable polymers with controlled molecular weights, different functionalities and tunable properties.
Journal Article
Graphene electro-optic modulator with 30 GHz bandwidth
Scientists have realized a graphene electro-optic modulator operating with a 30 GHz bandwidth and with a state-of-the-art modulation efficiency of 1.5 dB V
−1
, paving the way for fast digital communications.
Graphene has generated exceptional interest as an optoelectronic material
1
,
2
because its high carrier mobility
3
,
4
and broadband absorption
5
promise to make extremely fast and broadband electro-optic devices possible
6
,
7
,
8
,
9
. Electro-optic graphene modulators previously reported, however, have been limited in bandwidth to a few gigahertz
10
,
11
,
12
,
13
,
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,
15
because of the large capacitance required to achieve reasonable voltage swings. Here, we demonstrate a graphene electro-optic modulator based on resonator loss modulation at critical coupling
16
that shows drastically increased speed and efficiency. Our device operates with a 30 GHz bandwidth and with a state-of-the-art modulation efficiency of 15 dB per 10 V. We also show the first high-speed large-signal operation in a graphene modulator, paving the way for fast digital communications using this platform. The modulator uniquely uses silicon nitride waveguides, an otherwise completely passive material platform, with promising applications for ultra-low-loss broadband structures and nonlinear optics.
Journal Article