Alex K. Chen

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on the atlas — 90

highlights — 33

Current advanced semiconductor process nodes require multi-patterning4, a process where a single layer is exposed or processed multiple times to achieve finer feature pitches beyond the resolution of a lithography system. Template-based approaches work by defining an initial pattern and then using deposition and etching to multiply the number of lines, but because this process produces only parallel lines, it often restricts signal routing to a single direction (1D) per metal layer. This drives the need for more metal layers and connections (vias) between them, introducing higher resistive-cap…
Information to Atoms - Substrate
Today in neuro: RoPE for brains? [R]otating waves, which propagate along a circular trajectory, were a prominent and frequently occurring feature [...] [T]hey may serve as a mechanism for coordinating information flow across sensory and motor systems.
Gabriele Sarti on X: "Today in neuro: RoPE for brains? [R]otating waves, which propagate along a circular trajectory, were a prominent and frequently occurring feature [...] [T]hey may serve as a mechanism for coordinating information flow across sensory and motor systems. https://t.co/Ol8kNPDvib" / X
The Dirichlet energy: E D ( f ) = f T L f = ∑ ( i , j ) ∈ E w i j ( f i − f j ) 2 measures the "roughness" of a signal f on the graph—how much it varies across edges. Minimizing Dirichlet energy produces smooth functions that respect graph structure. This is precisely the discrete analog of Landau's gradient term
Crystals in NNs: Technical Companion Piece — LessWrong
Will the US solve manufacturing with AI? Well, maybe, because superintelligence is supposed to solve everything. But there’s a risk that AI will destabilize society before it fixes the industrial base. When I walk around the library at Stanford, I see students plugging everything into AI tools; when they need a break, they’re watching short-form videos on their phones. These videos have been marvelously transformed by AI tools. Shortly after OpenAI released Sora 2, I had brunch with a friend who told me that he created an AI video of himself expertly breakdancing that fooled his five-year-old;…
2025 letter | Dan Wang
The neural structures that shape electrical activity in the brain take a bit longer to degrade, on a time scale of minutes to hours, but they too begin to degrade quickly. One study found that structural changes to dendrites, which are membrane extensions of neurons, can begin to occur within three minutes of lack of blood flow (Murphy et al., 2008). However, as we will discuss later, some neural structures can take hours or even days to degrade.
Towards a more accurate definition of death
2. Lipid composition could affect the capacitance properties of the membranes, which are based on membrane thickness and the dielectric constant (Niebur, 2008). For example, higher levels of cell membrane cholesterol are associated with thicker cell membranes (Postila et al., 2020). In addition to ion concentration gradients, the electrical gradient across the membrane affects how ions will flow into and out of the cell. However, evidence has suggested that capacitance varies only slightly across cell types and very little with different densities of proteins embedded in the membrane (Gentet e…
Biomolecules: the building blocks of engrams
During the curing process, the glass transition temperature rises as the embedding agent polymerizes. Vitrification occurs when the glass transition temperature is equal to or greater than the temperature of the sample that is being cured. At this point, there is generally a dramatic slowing of the cure rate, as the viscosity of the material is so high that the polymerization reactions are very slow. This, in turn, slows the increase of the glass transition temperature. As a result, the glass transition temperature of the resulting polymerized resin is limited by the curing temperature.
Notes on embedding for brain preservation
A major trade-off is that a higher crosslink density and glass transition temperature will tend to the material more brittle and fractures more likely at a given storage temperature (Utaloff et al., 2019). This is the same phenomenon as is seen in vitrification by cold temperatures, where storage further below the glass transition temperature tends to make fractures more common.
Notes on embedding for brain preservation
Due to the stringent photon-count requirements of voltage imaging and the modest voltage sensitivity of existing reporters, 2P voltage imaging in vivo faces a stringent tradeoff between shot noise and tissue photodamage. 2P imaging of hundreds of neurons with high SNR at a depth of > 300 μ m > 300 𝜇 m will require either major improvements in 2P GEVIs or qualitatively new approaches to imaging.
Optical constraints on two-photon voltage imaging
Foundation models have been proposed for data formats which have resisted conventional large-scale machine learning, e.g. graph data, spikes, transcriptomics, etc.
Foundation models for neuroscience - by Patrick Mineault
Foundation models have been proposed for data formats which have resisted conventional large-scale machine learning, e.g. graph data, spikes, transcriptomics, etc.
Foundation models for neuroscience - by Patrick Mineault
What we want is a flourishing ecosystem of people with wildly imaginative and insightful ideas for new social processes; and for those ideas to be tested and the best ideas scaled out
A Vision of Metascience
probability of loss of function intolerance (pLI
Tissue-specific impacts of aging and genetics on gene expression patterns in humans | Nature Communications
Even a super powerful recursive self-optimizing machine initially starts with some seed utility/objective function at the very core. Unfortunately it increasingly looks like efficiency strongly demands some form of inherently unsafe self-motivation utility function, such as empowerment or creativity, and self-motivated agentic utility functions are the natural strong attractor[8].
DL towards the unaligned Recursive Self-Optimization attractor - LessWrong
Science isn't laying pipe, either. And there's something surreal about the idea of doing RCTs (or RCT-likes) to compare quantitative valuations of different funding schemes. Can you imagine someone doing RCTs on poetry? On art schools? Shakespeare didn't learn to write using RCTs; nor did Picasso learn to paint that way. And Bauhaus wasn't the result of a series of carefully controlled methodological studies. Scientific institution building is, similarly, an act of imaginative creation. And given that, you might reasonably throw your hands up in the air and declare: "It's ridiculous to be comp…
The trouble in comparing different approaches to science funding
It's tempting to just nod along at all this. But it violates much of our intuition from everyday life, and from much conventional training. If you're a careful, analytically trained thinker, it's tempting to think that you should analyze venture capital by building a large body of evidence, perhaps by sampling a large number of companies. But if you believe Thiel, then the things you learn may, if you're not careful, actually be to your disadvantage. Why? Because by definition you'll be learning about merely good or great companies. That's the part of the curve you're trying to get away from: …
The trouble in comparing different approaches to science funding
It's tempting to just nod along at all this. But it violates much of our intuition from everyday life, and from much conventional training. If you're a careful, analytically trained thinker, it's tempting to think that you should analyze venture capital by building a large body of evidence, perhaps by sampling a large number of companies. But if you believe Thiel, then the things you learn may, if you're not careful, actually be to your disadvantage. Why? Because by definition you'll be learning about merely good or great companies. That's the part of the curve you're trying to get away from: …
The trouble in comparing different approaches to science funding
Along with learning and growing, I think I was also optimizing for recognition and validation. I said things I didn’t 100% understand (ex. impact billions) just to sound smart, posted resources in slack with a question that I didn’t really care about what the answer was, to give off a facade that I was thoughtful. Whenever I talked about the projects I worked on, I always felt a mild pang of uneasiness because none of them really amounted to anything, they were like trial runs of a game where I played it for a bit but it never really got anywhere, nothing real, nothing I truly believed in. It …
Reflections on 2021 - by Amy Li - Amy's Monthly Updates
e together and form inappropriate chemical bonds in a process called cross-linking. This makes the skin stiffen and lose elasticity, and we get wrinkles.
Six ways metabolic health affects longevity - Levels
the L1 cache 100 times in a row. The L1 cache has a 1ns access latency and a 100 percent hit rate. It, therefore, takes our CPU 100 nanoseconds to perform this operation.
How L1 and L2 CPU Caches Work, and Why They're an Essential Part of Modern Chips - ExtremeTech
ich high resolution structural information was not available. We classified these models into groups based on their biological functions, and provide examples of complexes in each functional class in Figs. 2-4. A first set of complexes are involved in maintenance and processing of genetic information: DNA repair, mitosis and meiosis checkpoints, transcription, and translation (Fig. 2). A second set of complexes play roles in protein translocation, transport through the secretory pathway, the cytoskeleton and cell organelles (Fig. 3). A third set of complexes are involved in metabolism (Fig. 4)…
Computed structures of core eukaryotic protein complexes
ensated for the disruption. While voting records are protected with zero-knowledge proofs, decision outcomes and consensus statements are transparently recorded, so if you find a new construction site across the street, you know exactly
Turing-Complete Governance — Mirror
Dendrimers can be prepared with a level of control not attainable with most linear polymers, leading to nearly monodisperse, globular macromolecules with a large number of peripheral groups as seen in Figure 2
Dendrimers: synthesis, applications, and properties
the detection of localized mRNAs in dendrites, spines, axons, and growth cones of cultured neurons; or digoxigenin
Neuronal lineage marker
[-]PhoenixFriend4d 89 I'm a present or past CFAR employee commenting anonymously to avoid retribution. I believe that the dynamics of the organization grew to be significantly more cult-like than the OP and readers realize. I say all this with the hope that future-CFAR will emerge like a phoenix, leaving these issues in the ashes. At least four people who did not listen to Michael's pitch about societal corruption and worked in some capacity with the CFAR/MIRI team had psychotic episodes. Psychedelic use was common among the leadership of CFAR and spread through imitation, if not actual instit…
My experience at and around MIRI and CFAR (inspired by Zoe Curzi's writeup of experiences at Leverage) - LessWrong
Fetal alcohol syndrome (FAS) may be due to persistent ethanol consumption by mother during pregnancy. Newborn with FAS have defective intelligence, motor function and hyperactivity. The mechanism of this brain damage remains elusive. Nonetheless, ethanol consumption is hypothesized to affect the accumulation of DHA in brain development in which this fatty acid is required for the synthesis of plasmalogens in peroxisomes. Another finding also revealed that developing and adult brains have lower DHA and plasmalogen levels in neural membranes with ethanol exposure (Wing D R et al., 1982; Hofteig …
About Plasmalogens - Scallop-derived PLASMALOGEN
guards against depletion and overproduction of HSCs. Disruption of these regulatory mechanisms can result in blood disease, such as BM failure or leukemia. Transforming growth factor-β (TGF-β) is the founding member of a large family of secreted polypeptide growth factors, consisting of over 30 members in humans, including activins, bone morphogenetic proteins (BMPs), and others.5 The TGF-β family constitutes a multifunctional set of cytokines that regulate a bewildering array of
TGF-β signaling in the control of hematopoietic stem cells | Blood | American Society of Hematology
the real argument for decentralization is not that centralized systems are broken. It’s that they are so functional that only a radical redistribution of control and ownership could wedge new opportunities to create more equity.
Tweets liked by Alex K. Chen (Longevity+Accelerando protagonist) (@InquilineKea) / Twitter
Alastair @_AlastairX_ · Sep 26 - Charisma is easy to see - Humor in leaders is underrated - "an abundance of reputational short-sellers" - Sales output is very correlated with input, software output less so - Past a threshold of intelligence, energy becomes a better predictor of success
Tweets liked by Alex K. Chen (Longevity+Accelerando protagonist) (@InquilineKea) / Twitter
Alastair @_AlastairX_ · Sep 26 - Charisma is easy to see - Humor in leaders is underrated - "an abundance of reputational short-sellers" - Sales output is very correlated with input, software output less so - Past a threshold of intelligence, energy becomes a better predictor of success
Tweets liked by Alex K. Chen (Longevity+Accelerando protagonist) (@InquilineKea) / Twitter
I have this "feeling" that doing deep learning with classical/quantum chemical simulation is easier than experimental data since sim inputs are so sparse (coordinates/sim parameters). I just learned there is a way to quantify this: Kolmogorov complexity.
Tweets liked by Alex K. Chen (Longevity+Accelerando protagonist) (@InquilineKea) / Twitter
your page. Capture what you learn while you
Curius / Bookmarks for the extremely curious
Non-linear interactions means that results are often context-specific. A protein will kill one cell type and protect another. Nothing is "better" or "worse", but shift a system in a way that may be desired.
Marley's Bookshelf / Curius