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MIT Open Access Articles

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  1. Preservation and detectability of shock-induced magnetization

    Swanson-Hysell, Nicholas L.; Cournède, Cécile; Tikoo, Sonia M.; Gattacceca, Jerome; Weiss, Benjamin P; Suavet, Clement Romain
    An understanding of the effects of hypervelocity impacts on the magnetization of natural samples is required for interpreting paleomagnetic records of meteorites, lunar rocks, and cratered planetary surfaces. Rocks containing ferromagnetic minerals have been shown to acquire shock remanent magnetization (SRM) due to the passage of a shock wave in the presence of an ambient magnetic field. In this study, we conducted pressure remanent magnetization (PRM) acquisition experiments on a variety of natural samples as an analog for SRM acquisition at pressures ranging up to 1.8 GPa. Comparison of the alternating field (AF) and thermal demagnetization behavior of PRM confirms that...

  2. Spatial variations in the rate of sea level rise caused by the present-day melting of glaciers and ice sheets

    Conrad, Clinton P.; Hager, Bradford H
    The redistribution of surface water mass associated with the melting of glacial ice causes uplift near areas of mass depletion, depression of the seafloors, and changes in the earth's gravitational field which perturb the ocean surface. As a result, local spatial variations exist in the rate of sea level rise. Tide gauges on continental coastlines measure a sea level rise 5% smaller than the global average. Tide gauges in the hemisphere opposite a source of continental mass depletion measure sea level rise 10 to 20% greater than the global average produced by that source while satellites make measurements 10% too...

  3. Characterisation of liver pathogenesis, human immune responses and drug testing in a humanised mouse model of HCV infection

    Keng, Choong Tat; Sze, Ching Wooen; Zheng, Dahai; Zheng, Zhiqiang; Yong, Kylie Su Mei; Tan, Shu Qi; Ong, Jessica Jie Ying; Tan, Sue Yee; Loh, Eva; Upadya, Megha Haridas; Kuick, Chik Hong; Hotta, Hak; Lim, Seng Gee; Tan, Thiam Chye; Chang, Kenneth T E; Hong, Wanjin; Tan, Yee-Joo; Chen, Qingfeng; Chen, Jianzhu
    Objective HCV infection affects millions of people worldwide, and many patients develop chronic infection leading to liver cancers. For decades, the lack of a small animal model that can recapitulate HCV infection, its immunopathogenesis and disease progression has impeded the development of an effective vaccine and therapeutics. We aim to provide a humanised mouse model for the understanding of HCV-specific human immune responses and HCV-associated disease pathologies. Design Recently, we have established human liver cells with a matched human immune system in NOD-scid Il2rg−/− (NSG) mice (HIL mice). These mice are infected with HCV by intravenous injection, and the pathologies are...

  4. Co-Culture of Tumor Spheroids and Fibroblasts in a Collagen Matrix-Incorporated Microfluidic Chip Mimics Reciprocal Activation in Solid Tumor Microenvironment

    Jeong, Su-Yeong; Lee, Ji-Hyun; Chung, Seok; Kuh, Hyo-Jeong; Shin, Yoojin
    Multicellular 3D culture and interaction with stromal components are considered essential elements in establishing a ‘more clinically relevant’ tumor model. Matrix-embedded 3D cultures using a microfluidic chip platform can recapitulate the microscale interaction within tumor microenvironments. As a major component of tumor microenvironment, cancer-associated fibroblasts (CAFs) play a role in cancer progression and drug resistance. Here, we present a microfluidic chip-based tumor tissue culture model that integrates 3D tumor spheroids (TSs) with CAF in proximity within a hydrogel scaffold. HT-29 human colorectal carcinoma cells grew into 3D TSs and the growth was stimulated when co-cultured with fibroblasts as shown by...

  5. Human-robot co-navigation using anticipatory indicators of human walking motion

    Unhelkar, Vaibhav Vasant; Perez D'Arpino, Claudia; Shah, Julie A; Stirling, Leia A.
    Mobile, interactive robots that operate in human-centric environments need the capability to safely and efficiently navigate around humans. This requires the ability to sense and predict human motion trajectories and to plan around them. In this paper, we present a study that supports the existence of statistically significant biomechanical turn indicators of human walking motions. Further, we demonstrate the effectiveness of these turn indicators as features in the prediction of human motion trajectories. Human motion capture data is collected with predefined goals to train and test a prediction algorithm. Use of anticipatory features results in improved performance of the prediction...

  6. A natural language planner interface for mobile manipulators

    Tellex, Stefanie; Howard, Thomas M.; Roy, Nicholas
    Natural language interfaces for robot control aspire to find the best sequence of actions that reflect the behavior intended by the instruction. This is difficult because of the diversity of language, variety of environments, and heterogeneity of tasks. Previous work has demonstrated that probabilistic graphical models constructed from the parse structure of natural language can be used to identify motions that most closely resemble verb phrases. Such approaches however quickly succumb to computational bottlenecks imposed by construction and search the space of possible actions. Planning constraints, which define goal regions and separate the admissible and inadmissible states in an environment...

  7. Time response of increases in ATP and muscle resistance to fatigue after low-level laser (light) therapy (LLLT) in mice

    Ferraresi, Cleber; Huang, Ying-Ying; de Sousa, Marcelo Victor Pires; Bagnato, Vanderlei Salvador; Parizotto, Nivaldo Antonio; Hamblin, Michael R
    Recently, low-level laser (light) therapy has been used to increase muscle performance in intense exercises. However, there is a lack of understanding of the time response of muscles to light therapy. The first purpose of this study was to determine the time response for light-emitting diode therapy (LEDT)-mediated increase in adenosine triphosphate (ATP) in the soleus and gastrocnemius muscles in mice. Second purpose was to test whether LEDT can increase the resistance of muscles to fatigue during intense exercise. Fifty male Balb/c mice were randomly allocated into two equal groups: LEDT-ATP and LEDT-fatigue. Both groups were subdivided into five equal...

  8. Low-level laser therapy (LLLT) combined with swimming training improved the lipid profile in rats fed with high-fat diet

    Sene-Fiorese, Marcela; Aquino, Antonio E.; Paolillo, Fernanda R.; Duarte, Fernanda O.; Oishi, Jorge C.; Pena, Airton A.; Duarte, Ana C. G. O.; Bagnato, Vanderlei S.; Parizotto, Nivaldo A.; Hamblin, Michael R
    Obesity and associated dyslipidemia is the fastest growing health problem throughout the world. The combination of exercise and low-level laser therapy (LLLT) could be a new approach to the treatment of obesity and associated disease. In this work, the effects of LLLT associated with exercises on the lipid metabolism in regular and high-fat diet rats were verified. We used 64 rats divided in eight groups with eight rats each, designed: SC, sedentary chow diet; SCL, sedentary chow diet laser, TC, trained chow diet; TCL, trained chow diet laser; SH, sedentary high-fat diet; SHL, sedentary high-fat diet laser; TH, trained high-fat...

  9. Low-level laser therapy (808 nm) contributes to muscle regeneration and prevents fibrosis in rat tibialis anterior muscle after cryolesion

    Assis, Lívia; Moretti, Ana Iochabel Soares; Abrahão, Thalita Balsamo; de Souza, Heraldo Possolo; Parizotto, Nivaldo Antonio; Hamblin, Michael R
    Muscle regeneration is a complex phenomenon, involving replacement of damaged fibers by new muscle fibers. During this process, there is a tendency to form scar tissue or fibrosis by deposition of collagen that could be detrimental to muscle function. New therapies that could regulate fibrosis and favor muscle regeneration would be important for physical therapy. Low-level laser therapy (LLLT) has been studied for clinical treatment of skeletal muscle injuries and disorders, even though the molecular and cellular mechanisms have not yet been clarified. The aim of this study was to evaluate the effects of LLLT on molecular markers involved in...

  10. An introduction to the special issue on cross-community mining

    Guo, Bin; Yu, Zhiwen; Pereira, Francisco
    People now live in heterogeneous social communities within cyber-physical spaces—both online communities (e.g., Flickr, Google+, LinkedIn) and social networks where digital content is exchanged, and opportunistic or offline communities that exploit opportunistic relationships between pairs of networked devices to exchange content (built on mobile ad hoc networking techniques) [1]. These communities have different technical features which lead to distinct kinds of interaction—such as patterns of comments and likes in online communities and co-location in offline communities, or issues of friendship, trust and influence in online communities and social popularity, and movement patterns in offline communities. We further envision the rapid...

  11. MarcoPolo-R near earth asteroid sample return mission

    Michel, P.; Böhnhardt, H.; Campo Bagatin, A.; Cerroni, P.; Dotto, E.; Fitzsimmons, A.; Lara, L.-M.; Licandro, J.; Marty, B.; Muinonen, K.; Nathues, A.; Oberst, J.; Robert, F.; Saladino, R.; Ulamec, S.; Zolensky, M.; Barucci, Maria Antonietta; Cheng, A. F.; Benner, L. A. M.; Bland, P. A.; Brucato, J. R.; Franchi, I. A.; Green, S. F.; Rivkin, A. S.; Trigo-Rodriguez, J. M.; Binzel, Richard P
    MarcoPolo-R is a sample return mission to a primitive Near-Earth Asteroid (NEA) proposed in collaboration with NASA. It will rendezvous with a primitive NEA, scientifically characterize it at multiple scales, and return a unique sample to Earth unaltered by the atmospheric entry process or terrestrial weathering. MarcoPolo-R will return bulk samples (up to 2 kg) from an organic-rich binary asteroid to Earth for laboratory analyses, allowing us to: explore the origin of planetary materials and initial stages of habitable planet formation; identify and characterize the organics and volatiles in a primitive asteroid; understand the unique geomorphology, dynamics and evolution of...

  12. Defending the Possibility of Knowledge

    Kennedy, Neil
    In this paper, I propose a solution to Fitch’s paradox that draws on ideas from Edgington (Mind 94:557–568, 1985), Rabinowicz and Segerberg (1994) and Kvanvig (Noûs 29:481–500, 1995). After examining the solution strategies of these authors, I will defend the view, initially proposed by Kvanvig, according to which the derivation of the paradox violates a crucial constraint on quantifier instantiation. The constraint states that non-rigid expressions cannot be substituted into modal positions. We will introduce a slightly modified syntax and semantics that will help underline this point. Furthermore, we will prove results about the consistency of verificationism and the principle...

  13. Dynamic Elastic Tides

    Wisdom, Jack; Meyer, Jennifer Ann
    This is an exploration of dynamic tides on elastic bodies. The body is thought of as a dynamical system described by its modes of oscillation. The dynamics of these modes are governed by differential equations that depend on the rheology. The modes are damped by dissipation. Tidal friction occurs as exterior bodies excite the modes and the modes act back on the tide raising body. The whole process is governed by a closed set of differential equations. Standard results from tidal theory are recovered in a two-timescale approximation to the solution of these differential equations.

  14. Seismic microzonation for Muscat region, Sultanate of Oman

    El-Hussain, I.; Deif, A.; Al-Jabri, K.; Al-Rawas, G.; Sundararajan, N.; El-Hady, S.; Al-Hashmi, S.; Al-Toubi, K.; Al-Saifi, M.; Al-Habsi, Z.; Mohamed, A. M. E.; Toksoz, M. Nafi
    Site characterization was carried out for Muscat region using the ambient noise measurements applying the horizontal-to-vertical spectral ratio (HVSR) technique and using active seismic survey utilizing the multichannel analysis of surface waves (MASW) of survey data. Microtremors measurements were carried out at 459 sites using short-period sensors. This extensive survey allowed the fundamental resonance frequency of the soft soil to be mapped and areas prone to site amplification to be identified. The results indicate a progressive decrease in the fundamental resonance frequencies from the southern and eastern parts, where the bedrock outcrops, toward the northern coast where a thickness of...

  15. Exact Time Evolution of the Asymmetric Hubbard Dimer

    Freericks, J. K.; Balasubramanian, Shankar N.
    We examine the time evolution of an asymmetric Hubbard dimer, which has a different on-site interaction on the two sites. The Hamiltonian has a time-dependent hopping term, which can be employed to describe an electric field (which creates a Hamiltonian with complex matrix elements), or it can describe a modulation of the lattice (which has real matrix elements). By examining the symmetries under spin and pseudospin, we show that the former case involves at most a 3 × 3 block—it can be mapped onto the time evolution of a time-independent Hamiltonian, so the dynamics can be evaluated analytically and exactly...

  16. Hysteresis-Based Switching Design for Stabilization of Switched Linear Neutral Systems

    Li, Tai-Fang; Niu, Ben; Fu, Jun
    The paper studies the problem of asymptotically stabilizing a class of switched linear neutral systems, where none of the individual subsystems is stabilizable. A co-design of a set of candidate controllers and a hysteresis-based switching strategy is developed to achieve asymptotic stability of the closed-loop switched neutral systems. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.

  17. SCOPA and META-SCOPA: software for the analysis and aggregation of genome-wide association studies of multiple correlated phenotypes

    Mägi, Reedik; Kaakinen, Marika; Fischer, Krista; Prokopenko, Inga; Clarke, Geraldine M.; Morris, Andrew P.; Suleymanov, Yury
    Background Genome-wide association studies (GWAS) of single nucleotide polymorphisms (SNPs) have been successful in identifying loci contributing genetic effects to a wide range of complex human diseases and quantitative traits. The traditional approach to GWAS analysis is to consider each phenotype separately, despite the fact that many diseases and quantitative traits are correlated with each other, and often measured in the same sample of individuals. Multivariate analyses of correlated phenotypes have been demonstrated, by simulation, to increase power to detect association with SNPs, and thus may enable improved detection of novel loci contributing to diseases and quantitative traits. Results We have developed the...

  18. An empirical study of the distribution of earthquakes with respect to rock type and depth

    Hager, Bradford H; Tal, Yuval
    Whether fault slip occurs seismically or aseismically depends on the frictional properties of the fault, which might be expected to depend on rock type and depth, as well as other factors. To examine the effect of rock type and depth on the distribution of earthquakes, we compare geologic models of the San Francisco Bay and the Southern California regions to the distribution of seismicity. We normalize the number of earthquakes within each rock type and depth interval by the corresponding volume to determine the earthquake density. Earthquake density is determined primarily by depth, while whether the rock is sedimentary or...

  19. Pressure solution creep of random packs of spheres

    Bernabe, Yves; Evans, James Brian
    We performed numerical calculations of compaction in aggregates of spherical grains, using Lehner and Leroy's (2004, hereinafter LL) constitutive model of pressure solution at grain contacts. That model is founded on a local definition of the thermodynamic driving force and leads to a fully coupled formulation of elastic deformation, dissolution, and diffusive transport along the grain boundaries. The initial geometry of the aggregate was generated by random packing of spheres with a small standard deviation of the diameters. During the simulations, isostatic loading was applied. The elastic displacements at the contacts were calculated according to Digby's (1981) nonlinear contact force...

  20. Convergence of Developmental and Oncogenic Signaling Pathways at Transcriptional Super-Enhancers

    Hnisz, Denes; Schuijers, Jurian; Lin, Charles Y.; Abraham, Brian J.; Lee, Tong Ihn; Bradner, James E.; Weintraub, Abraham Selby; Young, Richard A
    Super-enhancers and stretch enhancers (SEs) drive expression of genes that play prominent roles in normal and disease cells, but the functional importance of these clustered enhancer elements is poorly understood, so it is not clear why genes key to cell identity have evolved regulation by such elements. Here we show that SEs consist of functional constituent units that concentrate multiple developmental signaling pathways at key pluripotency genes in embryonic stem cells and confer enhanced responsiveness to signaling of their associated genes. Cancer cells frequently acquire SEs at genes that promote tumorigenesis, and we show that these genes are especially sensitive to perturbation...

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