9,510 research outputs found
Irregular Satellites of the Planets: Products of Capture in the Early Solar System
All four giant planets in the Solar system possess irregular satellites,
characterized by large, highly eccentric and/or inclined orbits that are
distinct from the nearly circular, uninclined orbits of the regular satellites.
This difference can be traced directly to different modes of formation. Whereas
the regular satellites grew by accretion within circumplanetary disks the
irregular satellites were captured from initially heliocentric orbits at an
early epoch. Recently, powerful survey observations have greatly increased the
number of known irregular satellites, permitting a fresh look at the group
properties of these objects and motivating a re-examination of the mechanisms
of capture. None of the suggested mechanisms, including gas-drag, pull-down,
and three-body capture, convincingly fit the group characteristics of the
irregular satellites. The sources of the satellites also remain unidentified.Comment: 51 pages, 17 figures, 5 tables, to appear in ARAA 200
Optimization of cultivation conditions for extracellular lipase production by Yarrowia lipolytica using response surface method
A wild strain of Yarrowia lipolytica, identified as LMI 91, was isolated from an oleaginous Brazilian fruit called pequi (Caryocar brasiliense Camb), which is a native species of the Brazilian savannah and which acts as a potent lipase producer. The present study examined the effects of certain factors, such as the combination of casein and meat peptones, as well as the initial pH of a culture medium in lipase produced by Y. lipolytica LMI 91. Experiments were conducted within a low concentration of olive oil, at a temperature of 30°C and a fermentation time of 60 h, under orbital shaking. The response surface methodology was used to determine the optimum concentration of the constituents’ composition. A 22 experimental design with four axial points and three central points was employed in the optimization experiments, and interactive regression analysis was performed to obtain the optimum concentration. The experimental values were found to be in accordance with the predicted values, presenting a correlation coefficient of 0.866. The maximum lipase activity (13.0 U/mL) was obtained by peptone mixture of 70 g/L (1:1) and an initial pH of 5.0.Keywords: Yarrowia lipolytica, wild strain, extracellular lipase, fermentation, optimizationAfrican Journal of Biotechnology Vol. 12(17), pp. 2270-227
Functional MRI of the Reserpine-Induced Putative Rat Model of Fibromyalgia Reveals Discriminatory Patterns of Functional Augmentation to Acute Nociceptive Stimuli
Functional neuroimaging, applied to pre-clinical models of chronic pain, offers unique advantages in the drive to discover new treatments for this prevalent and oppressive condition. The high spatial and temporal resolution of fMRI affords detailed mapping of regional pharmacodynamics that underlie mechanisms of pain suppression by new analgesics. Despite evidence supporting the translational relevance of this approach, relatively few studies have investigated fMRI abnormalities in rodent models of chronic pain. In this study, we used fMRI to map the BOLD response in a recently developed putative rat model of fibromyalgia to innocuous and acute nociceptive stimuli by applying a step-wise graded electrical forepaw stimulation paradigm, with comparison to healthy controls. We observed discriminatory functional signatures (p < 0.001) to 2 mA electrical forepaw stimulation, found to be innocuous in the control group. As such, this translational approach provides sensitive and quantitative neural correlates of the underlying chronic disease. The regional patterns of functional augmentation were found to be concordant with previous studies of nociception in the anaesthetised rat brain, supporting the specificity of this approach in the study of altered central pain processing in reserpine induced myalgia. The methodology introduced in this work represents a novel platform for emerging treatment evaluation in highly experimentally controlled conditions
Monoclonal antibodies in neuro-oncology: Getting past the blood-brain barrier
Monoclonal antibodies (mAbs) are used with increasing success against many tumors, but for brain tumors the blood-brain barrier (BBB) is a special concern. The BBB prevents antibody entry to the normal brain; however, its role in brain tumor therapy is more complex. The BBB is closest to normal at micro-tumor sites; its properties and importance change as the tumor grows. In this review, evolving insight into the role of the BBB is balanced against other factors that affect efficacy or interpretation when mAbs are used against brain tumor targets. As specific examples, glioblastoma multiforme (GBM), primary central nervous system lymphoma (PCNSL) and blood-borne metastases from breast cancer are discussed in the context of treatment, respectively, with the mAbs bevacizumab, rituximab and trastuzumab, each of which is already widely used against tumors outside the brain. It is suggested that success against brain tumors will require getting past the BBB in two senses: physically, to better attack brain tumor targets, and conceptually, to give equal attention to problems that are shared with other tumor sites
Combinatorial RNA Design: Designability and Structure-Approximating Algorithm
In this work, we consider the Combinatorial RNA Design problem, a minimal
instance of the RNA design problem which aims at finding a sequence that admits
a given target as its unique base pair maximizing structure. We provide
complete characterizations for the structures that can be designed using
restricted alphabets. Under a classic four-letter alphabet, we provide a
complete characterization of designable structures without unpaired bases. When
unpaired bases are allowed, we provide partial characterizations for classes of
designable/undesignable structures, and show that the class of designable
structures is closed under the stutter operation. Membership of a given
structure to any of the classes can be tested in linear time and, for positive
instances, a solution can be found in linear time. Finally, we consider a
structure-approximating version of the problem that allows to extend bands
(helices) and, assuming that the input structure avoids two motifs, we provide
a linear-time algorithm that produces a designable structure with at most twice
more base pairs than the input structure.Comment: CPM - 26th Annual Symposium on Combinatorial Pattern Matching, Jun
2015, Ischia Island, Italy. LNCS, 201
The Turkey Ig-like receptor family: identification, expression and function.
The chicken leukocyte receptor complex located on microchromosome 31 encodes the chicken Ig-like receptors (CHIR), a vastly expanded gene family which can be further divided into three subgroups: activating CHIR-A, bifunctional CHIR-AB and inhibitory CHIR-B. Here, we investigated the presence of CHIR homologues in other bird species. The available genome databases of turkey, duck and zebra finch were screened with different strategies including BLAST searches employing various CHIR sequences, and keyword searches. We could not identify CHIR homologues in the distantly related zebra finch and duck, however, several partial and complete sequences of CHIR homologues were identified on chromosome 3 of the turkey genome. They were designated as turkey Ig-like receptors (TILR). Using cDNA derived from turkey blood and spleen RNA, six full length TILR could be amplified and further divided according to the typical sequence features into one activating TILR-A, one inhibitory TILR-B and four bifunctional TILR-AB. Since the TILR-AB sequences all displayed the critical residues shown to be involved in binding to IgY, we next confirmed the IgY binding using a soluble TILR-AB1-huIg fusion protein. This fusion protein reacted with IgY derived from various gallinaceous birds, but not with IgY from other bird species. Finally, we tested various mab directed against CHIR for their crossreactivity with either turkey or duck leukocytes. Whereas no staining was detectable with duck cells, the CHIR-AB1 specific mab 8D12 and the CHIR-A2 specific mab 13E2 both reacted with a leukocyte subpopulation that was further identified as thrombocytes by double immunofluorescence employing B-cell, T-cell and thrombocyte specific reagents. In summary, although the turkey harbors similar LRC genes as the chicken, their distribution seems to be distinct with predominance on thrombocytes rather than lymphocytes
Fatty Acid Profile and Bioactivity from Annona hypoglauca Seeds Oil
Plants from Annona (Annonaceae) genus are present in tropical regions, where they have economic and medicinal potential. Information on the fatty acids profile and bioactivity from seed oil of Annona species are incipient. The objective of this work was to investigate Annona hypoglauca seeds oil in terms of its yield, composition and biological activity (acetylcholinesterase enzyme inhibition, bactericidal and fungicidal activity). Fatty acids profiles were determined by Gas Chromatography equipped with Flame Ionization Detector. Oil yield reached about 15% and the major constituents detected were ω-9 oleic acid (42.65%) and ω-6 linoleic acid (29.63%). A. hypoglauca oil was potent for acetylcholinesterase inhibition (79.55%), and presented high and selective bioactivity against Candida albicans.Keywords: Annona hypoglauca, ω-9 Oleic Acid, ω-6 Linoleic Acid, Acetylcholinesterase, Candida albican
Group theoretical approach to quantum fields in de Sitter space I. The principal series
Using unitary irreducible representations of the de Sitter group, we
construct the Fock space of a massive free scalar field.
In this approach, the vacuum is the unique dS invariant state. The quantum
field is a posteriori defined by an operator subject to covariant
transformations under the dS isometry group. This insures that it obeys
canonical commutation relations, up to an overall factor which should not
vanish as it fixes the value of hbar. However, contrary to what is obtained for
the Poincare group, the covariance condition leaves an arbitrariness in the
definition of the field. This arbitrariness allows to recover the amplitudes
governing spontaneous pair creation processes, as well as the class of alpha
vacua obtained in the usual field theoretical approach. The two approaches can
be formally related by introducing a squeezing operator which acts on the state
in the field theoretical description and on the operator in the present
treatment. The choice of the different dS invariant schemes (different alpha
vacua) is here posed in very simple terms: it is related to a first order
differential equation which is singular on the horizon and whose general
solution is therefore characterized by the amplitude on either side of the
horizon. Our algebraic approach offers a new method to define quantum field
theory on some deformations of dS space.Comment: 35 pages, 2 figures ; Corrected typo, Changed referenc
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