664 research outputs found
Gut Microbial Changes, Interactions, and Their Implications on Human Lifecycle: An Ageing Perspective.
Gut microbiota is established during birth and evolves with age, mostly maintaining the commensal relationship with the host. A growing body of clinical evidence suggests an intricate relationship between the gut microbiota and the immune system. With ageing, the gut microbiota develops significant imbalances in the major phyla such as the anaerobic Firmicutes and Bacteroidetes as well as a diverse range of facultative organisms, resulting in impaired immune responses. Antimicrobial therapy is commonly used for the treatment of infections; however, this may also result in the loss of normal gut flora. Advanced age, antibiotic use, underlying diseases, infections, hormonal differences, circadian rhythm, and malnutrition, either alone or in combination, contribute to the problem. This nonbeneficial gastrointestinal modulation may be reversed by judicious and controlled use of antibiotics and the appropriate use of prebiotics and probiotics. In certain persistent, recurrent settings, the option of faecal microbiota transplantation can be explored. The aim of the current review is to focus on the establishment and alteration of gut microbiota, with ageing. The review also discusses the potential role of gut microbiota in regulating the immune system, together with its function in healthy and diseased state
Matched Pulse Propagation in a Three-Level System
The B\"{a}cklund transformation for the three-level Maxwell-Bloch equation is
presented in the matrix potential formalism. By applying the B\"{a}cklund
transformation to a constant electric field background, we obtain a general
solution for matched pulses (a pair of solitary waves) which can emit or absorb
a light velocity solitary pulse but otherwise propagate with their shapes
invariant. In the special case, this solution describes a steady state pulse
without emission or absorption, and becomes the matched pulse solution recently
obtained by Hioe and Grobe. A nonlinear superposition rule is derived from the
B\"{a}cklund transformation and used for the explicit construction of two
solitons as well as nonabelian breathers. Various new features of these
solutions are addressed. In particular, we analyze in detail the scattering of
"invertons", a specific pair of different wavelength solitons one of which
moving with the velocity of light. Unlike the usual case of soliton scattering,
the broader inverton changes its sign through the scattering. Surprisingly, the
light velocity inverton receives time advance through the scattering thereby
moving faster than light, which however does not violate causality.Comment: 20 pages, Latex, 12 eps figure files some comments and references are
added. postscript file with 12 figures can be obtained at
http://photon.kyunghee.ac.kr/~qhpark
Narrowing of EIT resonance in a Doppler Broadened Medium
We derive an analytic expression for the linewidth of EIT resonance in a
Doppler broadened system. It is shown here that for relatively low intensity of
the driving field the EIT linewidth is proportional to the square root of
intensity and is independent of the Doppler width, similar to the laser induced
line narrowing effect by Feld and Javan. In the limit of high intensity we
recover the usual power broadening case where EIT linewidth is proportional to
the intensity and inversely proportional to the Doppler width.Comment: 4 pages, 2 figure
Molecular mechanisms of intestinal inflammation leading to colorectal cancer
Inflammatory bowel disease (IBD) is recognized as a leading cause in the development of colorectal cancer (CRC). Inflammatory bowel disease associated colorectal cancer (IBD-CRC) is a growing healthcare burden, causing significant morbidity and mortality world-wide. In the present review, relevant preclinical models of IBD-CRC, a concise overview of potential molecular mechanisms that are involved and responsible for IBD associated colonic tumorigenesis along with the current and the future therapeutic approaches including the role of novel natural and synthetic compounds for the prevention and treatment of IBD-CRC are outlined. This review will benefit various clinicians and translational researchers working in the area of IBD-CRC to have a quick snap-shot of the ongoing trends in IBD-CRC research and discoveries
Phase-dependent spectra in a driven two-level atom
We propose a method to observe phase-dependent spectra in resonance
fluorescence, employing a two-level atom driven by a strong coherent field and
a weak, amplitude-fluctuating field. The spectra are similar to those which
occur in a squeezed vacuum, but avoid the problem of achieving squeezing over a
solid angle. The system shows other interesting features, such as
pronounced gain without population inversion.Comment: 4 pages and 4 figures. Submitted to Phys. Rev. Let
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