707 research outputs found
Closed FRW model in Loop Quantum Cosmology
The basic idea of the LQC applies to every spatially homogeneous cosmological
model, however only the spatially flat (so called ) case has been
understood in detail in the literature thus far. In the closed (so called: k=1)
case certain technical difficulties have been the obstacle that stopped the
development. In this work the difficulties are overcome, and a new LQC model of
the spatially closed, homogeneous, isotropic universe is constructed. The
topology of the spacelike section of the universe is assumed to be that of
SU(2) or SO(3). Surprisingly, according to the results achieved in this work,
the two cases can be distinguished from each other just by the local properties
of the quantum geometry of the universe. The quantum hamiltonian operator of
the gravitational field takes the form of a difference operator, where the
elementary step is the quantum of the 3-volume derived in the flat case by
Ashtekar, Pawlowski and Singh. The mathematical properties of the operator are
studied: it is essentially self-adjoint, bounded from above by 0, the 0 itself
is not an eigenvalue, the eigenvectors form a basis. An estimate on the
dimension of the spectral projection on any finite interval is provided.Comment: 19 pages, latex, no figures, high quality, nea
Effect of age of Japanese quail on physical and biochemical characteristics of eggs
The aim of the study was to investigate the effects of age of birds on egg quality in Japanese quail. The eggs were randomly selected from among all eggs laid on the same day when the birds were 15, 23 and 31 weeks old. At each time point, 90 fresh eggs were evaluated for their physical and biochemical characteristics. Egg weights were similar over time. At 23 and 31 weeks, the eggs had less shell than at 15 weeks. Crude fat and ash contents of the eggs increased with the age of the birds. Crude protein was also highest in eggs of the oldest quail. At 31 weeks old, the eggs were lowest in pH of yolk and white. Quail that were 23 and 31 weeks old laid eggs with significantly higher polyunsaturated fatty acid (PUFA) and lower saturated fatty acid (SFA) contents. The lowest cholesterol content was in egg yolks from 23-week-old quail. The oldest birds had the highest contents of sodium, potassium, zinc, selenium, copper, and manganese. The content and activity of lysozyme decreased with ageing of the birds. From the consumers’ point of view, eggs from older birds appeared to be the most valuable. At the same time, as the quail ages, the antibacterial properties of eggs deteriorate, which may indicate a shorter shelf life
Estimation of the stress related to conservative scoliosis therapy: an analysis based on BSSQ questionnaires
BACKGROUND: Adolescent girls treated with a brace for scoliosis are submitted to prolonged stress related to both the disease and the therapy. Currently proposed quality of life questionnaires are focused on the outcome of therapy. Bad Sobernheim Stress Questionnaire (BSSQ) enables monitoring of patients being under treatment with a brace or exercises. The aim of the study was to assess the stress level in conservatively managed scoliotic girls using BSSQ. MATERIALS AND METHODS: 111 girls, aged 14,2 ± 2,2 years, mean Cobb angle of the primary curve 42,8° ± 17,0° and mean Bunnell angle of 11,4° ± 4,5° were examined with two versions of BSSQ (Deformity and Brace). The analysis considered the type of treatment, curve location, correlation of the total score with age, Cobb angle and Bunnell rotation angle. RESULTS: The BSSQ Deformity revealed the median of 17 points in patients managed with exercises (from 4 to 24 points), 18 in patients managed with a brace (from 8 to 24 points) and 12 in patients before surgery (from 3 to 21 points). Braced patients who completed both questionnaires (n = 50) revealed significantly higher score with BSSQ Deformity (median = 18) comparing to BSSQ Brace (median = 9). There was a correlation between the total score of BSSQ Deformity and the Cobb angle (r = -0,34), Bunnell primary curve rotation (r = -0,34) and Bunnell sum of rotation (r = -0,33) but not with the age of patients. CONCLUSION: Scoliotic adolescents managed with exercises and brace suffered little stress from the deformity. The brace increased the level of stress over the stress induced by the deformity. The stress level correlated with clinical deformity (Bunnell angle), radiological deformity (Cobb angle) and the type of treatment (exercises, bracing, surgery). Bad Sobernheim Stress Questionnaires are simple and helpful in the management of girls treated conservatively for idiopathic scoliosis
Quantum constraints, Dirac observables and evolution: group averaging versus Schroedinger picture in LQC
A general quantum constraint of the form (realized in particular in Loop Quantum Cosmology models) is
studied. Group Averaging is applied to define the Hilbert space of solutions
and the relational Dirac observables. Two cases are considered. In the first
case, the spectrum of the operator is assumed to be
discrete. The quantum theory defined by the constraint takes the form of a
Schroedinger-like quantum mechanics with a generalized Hamiltonian
. In the second case, the spectrum is absolutely continuous
and some peculiar asymptotic properties of the eigenfunctions are assumed. The
resulting Hilbert space and the dynamics are characterized by a continuous
family of the Schroedinger-like quantum theories. However, the relational
observables mix different members of the family. Our assumptions are motivated
by new Loop Quantum Cosmology models of quantum FRW spacetime. The two cases
considered in the paper correspond to the negative and, respectively, positive
cosmological constant. Our results should be also applicable in many other
general relativistic contexts.Comment: RevTex4, 32 page
Transcending Big Bang in Loop Quantum Cosmology: Recent Advances
We discuss the way non-perturbative quantization of cosmological spacetimes
in loop quantum cosmology provides insights on the physics of Planck scale and
the resolution of big bang singularity. In recent years, rigorous examination
of mathematical and physical aspects of the quantum theory has led to a
consistent quantization which is consistent and physically viable and some
early ideas have been ruled out. The latter include so called `physical
effects' originating from modifications to inverse scale factors in the flat
models. The singularity resolution is understood to originate from the
non-local nature of curvature in the quantum theory and the underlying polymer
representation. Using an exactly solvable model various insights have been
gained. The model predicts a generic occurrence of bounce for states in the
physical Hilbert space and a supremum for the spectrum of the energy density
operator. It also provides answers to the growth of fluctuations, showing that
semi-classicality is preserved to an amazing degree across the bounce.Comment: Invited plenary talk at the Sixth International Conference on
Gravitation and Cosmology, IUCAA (Pune). 13 pages, 3 figure
RESULTS OF POSTSLAUGHTER EVALUATION OF CROSSBRED FATTENERS (ZŁOTNICKA SPOTTED X DUROC) AND PUREBRED FATTENERS (ZŁOTNICKA SPOTTED)
Experimental material consisted of 112 carcasses of crossbred fatteners (złp x dur) and 16 purebred animals (złp). The following traits were analyzed in postslaughter evaluation: carcass weight (kg), mean backfat thickness (mm), height of the longissimus dorsi muscle (mm) and lean meat percentage in the carcass (%). Based on the determined carcass weight and measurements of carcass leanness the carcasses were classified in the SEUROP system. Results of postslaughter evaluation indicate relatively low carcass leanness. In only 10% carcasses leanness exceeded 50 %, while 75% carcasses fell within the range from R to O in the EUROP classification. The breed of the sire had a highly significant effect on meatiness of fatteners. Pigs sired by Duroc boars were characterized by a significantly higher meatiness, irrespectively of sex, piggery, supplier and year of birth. Backfat thickness was significantly higher in the group of crosses sired by Złotnicka Spotted boars
Classical Setting and Effective Dynamics for Spinfoam Cosmology
We explore how to extract effective dynamics from loop quantum gravity and
spinfoams truncated to a finite fixed graph, with the hope of modeling
symmetry-reduced gravitational systems. We particularize our study to the
2-vertex graph with N links. We describe the canonical data using the recent
formulation of the phase space in terms of spinors, and implement a
symmetry-reduction to the homogeneous and isotropic sector. From the canonical
point of view, we construct a consistent Hamiltonian for the model and discuss
its relation with Friedmann-Robertson-Walker cosmologies. Then, we analyze the
dynamics from the spinfoam approach. We compute exactly the transition
amplitude between initial and final coherent spin networks states with support
on the 2-vertex graph, for the choice of the simplest two-complex (with a
single space-time vertex). The transition amplitude verifies an exact
differential equation that agrees with the Hamiltonian constructed previously.
Thus, in our simple setting we clarify the link between the canonical and the
covariant formalisms.Comment: 38 pages, v2: Link with discretized loop quantum gravity made
explicit and emphasize
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