40 research outputs found
An iterative method for extreme optics of two-level systems
We formulate the problem of a two-level system in a linearly polarized laser
field in terms of a nonlinear Riccati-type differential equation and solve the
equation analytically in time intervals much shorter than half the optical
period. The analytical solutions for subsequent intervals are then stuck
together in an iterative procedure to cover the scale time of the laser pulse.
This approach is applicable to pulses of arbitrary (nonrelativistic) strengths,
shapes and durations, thus covering the whole region of light-matter couplings
from weak through moderate to strong ones. The method allows quick insight into
different problems from the field of light--matter interaction. Very good
quality of the method is shown by recovering with it a number of subtle effects
met in earlier numerically calculated photon-emission spectra from model
molecular ions, double quantum wells, atoms and semiconductors. The method
presented is an efficient mathematical tool to describe novel effects in the
region of, e.g., extreme nonlinear optics, i.e., when two--level systems are
exposed to pulses of only a few cycles in duration and strength ensuring the
Rabi frequency to approach and even exceed the laser light frequence
Methodological advances in imaging intravital axonal transport.
Axonal transport is the active process whereby neurons transport cargoes such as organelles and proteins anterogradely from the cell body to the axon terminal and retrogradely in the opposite direction. Bi-directional transport in axons is absolutely essential for the functioning and survival of neurons and appears to be negatively impacted by both aging and diseases of the nervous system, such as Alzheimer's disease and amyotrophic lateral sclerosis. The movement of individual cargoes along axons has been studied in vitro in live neurons and tissue explants for a number of years; however, it is currently unclear as to whether these systems faithfully and consistently replicate the in vivo situation. A number of intravital techniques originally developed for studying diverse biological events have recently been adapted to monitor axonal transport in real-time in a range of live organisms and are providing novel insight into this dynamic process. Here, we highlight these methodological advances in intravital imaging of axonal transport, outlining key strengths and limitations while discussing findings, possible improvements, and outstanding questions
Cardiolipin Synthesis in Brown and Beige Fat Mitochondria Is Essential for Systemic Energy Homeostasis
The beta secretase BACE1 regulates the expression of insulin receptor in the liver
Insulin receptor (IR) plays a key role in the control of glucose homeostasis; however, the regulation of its cellular expression remains poorly understood. Here we show that the amount of biologically active IR is regulated by the cleavage of its ectodomain, by the β-site amyloid precursor protein cleaving enzyme 1 (BACE1), in a glucose concentration-dependent manner. In vivo studies demonstrate that BACE1 regulates the amount of IR and insulin signaling in the liver. During diabetes, BACE1-dependent cleavage of IR is increased and the amount of IR in the liver is reduced, whereas infusion of a BACE1 inhibitor partially restores liver IR. We suggest the potential use of BACE1 inhibitors to enhance insulin signaling during diabetes. Additionally, we show that plasma levels of cleaved IR reflect IR isoform A expression levels in liver tumors, which prompts us to propose that the measurement of circulating cleaved IR may assist hepatic cancer detection and management
Microwave assisted wolff rearrangement: A facile method for the synthesis of Fmoc-β-amino acids
Modelling short-term effects of sulphur dioxide. 1. A model for the flux of SO2 into leaves and effects on leaf photosynthesis
Photochemical activity, photosynthetic pigments and carbohydrates in poplar leaves fumigated with sulphur dioxide
The purpose of this study was to assess the influence of SO2 on photosynthetic apparatus and the level of total nonstructural carbohydrates (TNC) in developing and mature leaves of poplar (Populus deltoides). Photosynthetic apparatus was evaluated on the basis of fluorescence parameters (Fv/Fm, OPSII, qP and Rfd) and photosynthetic pigments (chlorophylls and carotenoids). Cuttings of poplar were exposed to 0.25 ppm of SO2 at 25°C and 200-300 mmol m-2s-1 PAR for 6 hours daily during 5 days in a fumigation chamber. The fumigation did not produce any significant differences in fluorescence parameters in neither developing nor mature leaves. In some mature leaves the concentration of pigments increased under the influence of SO2. Soluble carbohydrates decreased significantly both in developing and mature leaves and this was accompanied with an increase in starch accumulation. We suggest that Populus deltoides is a species tolerant to sulphur dioxide and the used SO2 dosage did not significantly impair the light reactions of photosynthesis, but it disturbed the accumulation of starch and the utilization of soluble carbohydrates in plants exposed to SO2
On a stochasticprocess determined by the conditional expectation and the conditionalvariance
Endoparasites of exotic ungulates from the Giraffidae and Camelidae families kept ex situ
Giraffes and camels are popular attractions at zoological gardens. In order to present the diversity of
parasites infecting exotic ungulates from zoos, faecal samples from three giraffes and six camels from both the Silesian
Zoological Garden in Chorzów, and Kraków Zoological Garden, were examined. The research was carried out over a
ten-month period in 2013 and 2014. In total, 100 faecal samples from 18 animals were analysed with the use of the
McMaster method. Moreover, coccidian oocysts were incubated to investigate their development and larvoscopic
examination was conducted to detect the presence of nematode species. Giraffes were infected with coccidia from the
genus Eimeria, and gastrointestinal nematodes from the Strongylida order, and Trichuris and Aonhotheca genera. One
male giraffe was uninfected. The level of infection in giraffes was low when compared to camels kept in both of the
zoos. Limited contact with other animal species contributed greatly to the lower level of infection in camels from
Kraków Zoo than those from Chorzów, which were kept in the same enclosure as alpacas and Shetland ponies