5,111 research outputs found
Adversarial nets with perceptual losses for text-to-image synthesis
Recent approaches in generative adversarial networks (GANs) can automatically
synthesize realistic images from descriptive text. Despite the overall fair
quality, the generated images often expose visible flaws that lack structural
definition for an object of interest. In this paper, we aim to extend state of
the art for GAN-based text-to-image synthesis by improving perceptual quality
of generated images. Differentiated from previous work, our synthetic image
generator optimizes on perceptual loss functions that measure pixel, feature
activation, and texture differences against a natural image. We present
visually more compelling synthetic images of birds and flowers generated from
text descriptions in comparison to some of the most prominent existing work
Adversarial Learning of Semantic Relevance in Text to Image Synthesis
We describe a new approach that improves the training of generative
adversarial nets (GANs) for synthesizing diverse images from a text input. Our
approach is based on the conditional version of GANs and expands on previous
work leveraging an auxiliary task in the discriminator. Our generated images
are not limited to certain classes and do not suffer from mode collapse while
semantically matching the text input. A key to our training methods is how to
form positive and negative training examples with respect to the class label of
a given image. Instead of selecting random training examples, we perform
negative sampling based on the semantic distance from a positive example in the
class. We evaluate our approach using the Oxford-102 flower dataset, adopting
the inception score and multi-scale structural similarity index (MS-SSIM)
metrics to assess discriminability and diversity of the generated images. The
empirical results indicate greater diversity in the generated images,
especially when we gradually select more negative training examples closer to a
positive example in the semantic space
Scaling anisotropy of the power in parallel and perpendicular components of the solar wind magnetic field
Power spectra of the components of the magnetic field parallel (Pzz) and perpendicular (Pzz+Pyy) to the local mean magnetic field direction were determined by wavelet methods from Ulyssesâ MAG instrument data during eighteen 10-day segments of its first North Polar pass at high latitude at solar minimum in 1995. The power depends on frequency f and the angle θ between the solar wind direction and the local mean field, and with distance from the Sun. This data includes the solar wind whose total power (Pxx + Pyy + Pzz) in magnetic fluctuations we previously reported depends on f and the angle θ nearly as predicted by the GS95 critical balance model of strong incompressible MHD turbulence. Results at much wider range of frequencies during six evenly-spaced 10-day periods are presented here to illustrate the variability and evolution with distance from the Sun. Here we investigate the aniso tropic scaling of Pzz(f,θ) in particular because it is a reduced form of the Poloidal (pseudo-Alfvenic) component of the (incompressible) fluctuations. We also report the much larger Pxx(f,θ)+Pyy(f,θ) which is (mostly) reduced from the Toroidal (Alfvenic, i.e., perpendicular to both B and k) fluctuations, and comprises most of the total power. These different components of the total power evolve and scale differently in the inertial range. We compare these elements of the magnetic power spectral tensor with âcritical balanceâ model predictions
Regulation and Effector Function of TH1 and TH2 Cells in Immunity to Bordetella Pertussis
The evaluation of vaccines for human use requires reliable models of infection, that are predictive of
protective efficacy. Traditionally whole cell pertussis vaccines (Pw) have been controlled using the
Kendrick test, which measures protection following intracerebral challenge with Bordetella pertussis.
However, this test is unsuitable for assessing the potency o f the new acellular pertussis vaccines (Pa).
In this study, it was demonstrated that protection in a murine respiratory challenge model correlates
with the protective efficacy of Pa and Pw in children, but vaccine potency could not be predicted on the
basis of antibody responses against individual antigens. Furthermore, the murine model was shown to
be a reliable method for the determination of consistency between different batches o f Pa and Pw. This
study highlights the possible applications of the murine model in the regulatory control and future
development of pertussis vaccines.
The murine model of infection has been used in the elucidation of the protective mechanisms
induced following immunization with Pw or Pa, revealing roles for both antibody and T-cells in
protection against B. p ertu ssis. It has been demonstrated that children still appear to be protected
against infection, despite a rapid decline in antibody levels after vaccination. In the murine model,
antibody levels quickly decline after immunization, but significant levels of protection were observed
following aerosol challenge. Recall T-cell responses detectable for prolonged periods after
immunization, together with an anamnestic antibody response post-challenge suggest that
immunological memory is more significant in protection, than the induction of immediate antibody
responses in vaccine-induced protection against B. pertussis.
It has been demonstrated that Thl responses and particularly the cytokine IFN-y, play a
critical role in immunity to B. pertussis. In the present study, the role of IL-12 and IL-18 in the
induction of a protective Thl response to B. p ertu ssis was examined. Lack of IL-12 during primary
and secondary infection effected protection only at the early stages of infection, suggesting that IL-12
plays an important role at the induction stage of the immune response to B. pertussis, but also suggests
that other cytokines may be involved. IL-18 is rapidly produced in the lungs of B. p ertu ssis infected
IL-1 2~'~ and wild-type mice, which may compensate for the lack of IL-12 at the later stages of
infection.
The importance of Thl responses and IFN-y were fiirther highlighted in this study, through the
investigation of the effect of helminth infection on the outcome o f B. p ertu ssis infection, or
immunization with Pw. Infection with the parasite
Fasciolahepatica , was shown to suppress B.
pertussis-specific Thl responses, and delay bacterial clearance from the lungs, and was also shown to
inhibit this Thl response after it had become established. Furthermore, it was demonstrated that
infection with F. hepatic a was capable of downregulating the Thl response induced by systemic
immunization with Pw, and reducing its protective efficacy. In addition, a role for IL-4 was
demonstrated in the parasite-induced immunoregulation
Regulation and Effector Function of TH1 and TH2 Cells in Immunity to Bordetella Pertussis
The evaluation of vaccines for human use requires reliable models of infection, that are predictive of
protective efficacy. Traditionally whole cell pertussis vaccines (Pw) have been controlled using the
Kendrick test, which measures protection following intracerebral challenge with Bordetella pertussis.
However, this test is unsuitable for assessing the potency o f the new acellular pertussis vaccines (Pa).
In this study, it was demonstrated that protection in a murine respiratory challenge model correlates
with the protective efficacy of Pa and Pw in children, but vaccine potency could not be predicted on the
basis of antibody responses against individual antigens. Furthermore, the murine model was shown to
be a reliable method for the determination of consistency between different batches o f Pa and Pw. This
study highlights the possible applications of the murine model in the regulatory control and future
development of pertussis vaccines.
The murine model of infection has been used in the elucidation of the protective mechanisms
induced following immunization with Pw or Pa, revealing roles for both antibody and T-cells in
protection against B. p ertu ssis. It has been demonstrated that children still appear to be protected
against infection, despite a rapid decline in antibody levels after vaccination. In the murine model,
antibody levels quickly decline after immunization, but significant levels of protection were observed
following aerosol challenge. Recall T-cell responses detectable for prolonged periods after
immunization, together with an anamnestic antibody response post-challenge suggest that
immunological memory is more significant in protection, than the induction of immediate antibody
responses in vaccine-induced protection against B. pertussis.
It has been demonstrated that Thl responses and particularly the cytokine IFN-y, play a
critical role in immunity to B. pertussis. In the present study, the role of IL-12 and IL-18 in the
induction of a protective Thl response to B. p ertu ssis was examined. Lack of IL-12 during primary
and secondary infection effected protection only at the early stages of infection, suggesting that IL-12
plays an important role at the induction stage of the immune response to B. pertussis, but also suggests
that other cytokines may be involved. IL-18 is rapidly produced in the lungs of B. p ertu ssis infected
IL-1 2~'~ and wild-type mice, which may compensate for the lack of IL-12 at the later stages of
infection.
The importance of Thl responses and IFN-y were fiirther highlighted in this study, through the
investigation of the effect of helminth infection on the outcome o f B. p ertu ssis infection, or
immunization with Pw. Infection with the parasite
Fasciolahepatica , was shown to suppress B.
pertussis-specific Thl responses, and delay bacterial clearance from the lungs, and was also shown to
inhibit this Thl response after it had become established. Furthermore, it was demonstrated that
infection with F. hepatic a was capable of downregulating the Thl response induced by systemic
immunization with Pw, and reducing its protective efficacy. In addition, a role for IL-4 was
demonstrated in the parasite-induced immunoregulation
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