5,046 research outputs found
Needle Tip Force Estimation using an OCT Fiber and a Fused convGRU-CNN Architecture
Needle insertion is common during minimally invasive interventions such as
biopsy or brachytherapy. During soft tissue needle insertion, forces acting at
the needle tip cause tissue deformation and needle deflection. Accurate needle
tip force measurement provides information on needle-tissue interaction and
helps detecting and compensating potential misplacement. For this purpose we
introduce an image-based needle tip force estimation method using an optical
fiber imaging the deformation of an epoxy layer below the needle tip over time.
For calibration and force estimation, we introduce a novel deep learning-based
fused convolutional GRU-CNN model which effectively exploits the
spatio-temporal data structure. The needle is easy to manufacture and our model
achieves a mean absolute error of 1.76 +- 1.5 mN with a cross-correlation
coefficient of 0.9996, clearly outperforming other methods. We test needles
with different materials to demonstrate that the approach can be adapted for
different sensitivities and force ranges. Furthermore, we validate our approach
in an ex-vivo prostate needle insertion scenario.Comment: Accepted for Publication at MICCAI 201
Creation of Entanglement between Two Electron Spins Induced by Many Spin Ensemble Excitations
We theoretically explore the possibility of creating spin entanglement by
simultaneously coupling two electronic spins to a nuclear ensemble. By
microscopically modeling the spin ensemble with a single mode boson field, we
use the time-dependent Fr\"{o}hlich transformation (TDFT) method developed most
recently [Yong Li, C. Bruder, and C. P. Sun, Phys. Rev. A \textbf{75}, 032302
(2007)] to calculate the effective coupling between the two spins. Our
investigation shows that the total system realizes a solid state based
architecture for cavity QED. Exchanging such kind effective boson in a virtual
process can result in an effective interaction between two spins. It is
discovered that a maximum entangled state can be obtained when the velocity of
the electrons matches the initial distance between them in a suitable way.
Moreover, we also study how the number of collective excitations influences the
entanglement. It is shown that the larger the number of excitation is, the less
the two spins entangle each other.Comment: 8 pages, 4 figure
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An Evolutionarily Threat-Relevant Odor Strengthens Human Fear Memory.
Olfaction is an evolutionary ancient sense, but it remains unclear to what extent it can influence routine human behavior. We examined whether a threat-relevant predator odor (2-methyl-2-thiazoline) would contextually enhance the formation of human fear memory associations. Participants who learned to associate visual stimuli with electric shock in this predator odor context later showed stronger fear responses to the visual stimuli than participants who learned in an aversiveness-matched control odor context. This effect generalized to testing in another odor context, even after extinction training. Results of a separate experiment indicate that a possible biological mechanism for this effect may be increased cortisol levels in a predator odor context. These results suggest that innate olfactory processes can play an important role in human fear learning. Modulatory influences of odor contexts may partly explain the sometimes maladaptive persistence of human fear memory, e.g., in post-traumatic stress disorders
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Corrigendum: An Evolutionarily Threat-Relevant Odor Strengthens Human Fear Memory
In Vivo Analysis of Trypanosoma cruzi Persistence Foci at Single-Cell Resolution
Infections with Trypanosoma cruzi are usually lifelong despite generating a strong adaptive immune response. Identifying the sites of parasite persistence is therefore crucial to understanding how T. cruzi avoids immune-mediated destruction. However, this is a major technical challenge, because the parasite burden during chronic infections is extremely low. Here, we describe an integrated approach involving comprehensive tissue processing, ex vivo imaging, and confocal microscopy, which allowed us to visualize infected host cells in murine tissue with exquisite sensitivity. Using bioluminescence-guided tissue sampling, with a detection level of 200 parasites, which we term mega-nests. In contrast, during the acute stage, when the total parasite burden is considerably higher and many cells are infected, nests containing >50 parasites are rarely found. In C3H/HeN mice, but not BALB/c mice, we identified skeletal muscle as a major site of persistence during the chronic stage, with most parasites being found in large mega-nests within the muscle fibers. Finally, we report that parasites are also frequently found in the skin during chronic murine infections, often in multiple infection foci. In addition to being a site of parasite persistence, this anatomical reservoir could play an important role in insect-mediated transmission and have implications for drug development.IMPORTANCETrypanosoma cruzi causes Chagas disease, the most important parasitic infection in Latin America. Major pathologies include severe damage to the heart and digestive tract, although symptoms do not usually appear until decades after infection. Research has been hampered by the complex nature of the disease and technical difficulties in locating the extremely low number of parasites. Here, using highly sensitive imaging technology, we reveal the sites of parasite persistence during chronic-stage infections of experimental mice at single-cell resolution. We show that parasites are frequently located in smooth muscle cells in the circular muscle layer of the colon and that skeletal muscle cells and the skin can also be important reservoirs. This information provides a framework for investigating how the parasite is able to survive as a lifelong infection, despite a vigorous immune response. It also informs drug development strategies by identifying tissue sites that must be accessed to achieve a curative outcome
Analytic Kramer kernels, Lagrange-type interpolation series and de Branges spaces
The classical Kramer sampling theorem provides a method for obtaining orthogonal sampling formulas. In particular, when the involved kernel is analytic in the sampling parameter it can be stated in an abstract setting of reproducing kernel Hilbert spaces of entire functions which includes as a particular case the classical Shannon sampling theory. This abstract setting allows us to obtain a sort of converse result and to characterize when the sampling formula associated with an analytic Kramer kernel can be expressed as a Lagrange-type interpolation series. On the other hand, the de Branges spaces of entire functions satisfy orthogonal sampling formulas which can be written as Lagrange-type interpolation series. In this work some links between all these ideas are established
Hepatitis C treatment: where are we now?
Chronic hepatitis C infection affects millions of people worldwide and confers significant morbidity and mortality. Effective treatment is needed to prevent disease progression and associated complications. Previous treatment options were limited to interferon and ribavirin regimens, which gave low cure rates and were associated with unpleasant side effects. The era of direct acting antiviral (DAA) therapies began with the development of the first-generation of NS3/4A protease inhibitors (PI) in 2011. They vastly improved outcomes for patients, particularly those with genotype 1 infection, the most prevalent genotype globally. Since then a multitude of DAAs have been licensed for use and outcomes for patients have improved further, with fewer side effects and cure rates approaching 100%. Recent regimens are interferon-free, and in many cases, ribavirin-free and involve a combination of DAA agents. This review summarises the treatment options currently available and discusses potential barriers that may delay the global eradication of hepatitis C
Religious coping among African Americans, Caribbean Blacks and Non-Hispanic Whites
This study examined demographic predictors of attitudes regarding religious coping (i.e., prayer during stressful times and look to God for support, strength and guidance) within a national sample of African Americans, Caribbean Blacks, and non-Hispanic Whites (National Survey of American Life). The findings demonstrate significant Black-White differences in attitudes regarding religious coping with higher endorsements of religious coping among African Americans and Black Caribbeans (Caribbean Blacks). Comparisons of African Americans and Black Caribbeans revealed both similar and divergent patterns of demographic effects. For both African Americans and Black Caribbeans, women were more likely to utilize religious coping than men and married respondents were more likely than never married respondents to report utilizing prayer when dealing with a stressful situation. Further, for both groups, higher levels of education were associated with lower endorsements of the importance of prayer in dealing with stressful situations. Among African Americans only, Southerners were more likely than respondents who resided in other regions to endorse religious coping. Among Black Caribbeans, those who emigrated from Haiti were more likely than Jamaicans to utilize religious coping when dealing with a stressful episode. © 2008 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58064/1/20202_ftp.pd
Evaluation of a permeability-porosity relationship in a low permeability creeping material using a single transient test
A method is presented for the evaluation of the permeability-porosity
relationship in a low-permeability porous material using the results of a
single transient test. This method accounts for both elastic and non-elastic
deformations of the sample during the test and is applied to a hardened class G
oil well cement paste. An initial hydrostatic undrained loading is applied to
the sample. The generated excess pore pressure is then released at one end of
the sample while monitoring the pore pressure at the other end and the radial
strain in the middle of the sample during the dissipation of the pore pressure.
These measurements are back analysed to evaluate the permeability and its
evolution with porosity change. The effect of creep of the sample during the
test on the measured pore pressure and volume change is taken into account in
the analysis. This approach permits to calibrate a power law
permeability-porosity relationship for the tested hardened cement paste. The
porosity sensitivity exponent of the power-law is evaluated equal to 11 and is
shown to be mostly independent of the stress level and of the creep strains
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