569 research outputs found
Comment on "Acoustics of tachyon Fermi gas" [E. Trojan and G.V. Vlasov, arXiv:1103.2276 (hep-ph)]
In contrast to Trojan and Vlasov [arXiv:1103.2276 (hep-ph)], it is found that
an ideal Fermi gas of tachyons has a subluminous velocity of sound for any
particle density and, therefore, the causality condition for a tachyon gas
holds always true. Also, an ideal Fermi gas of tachyons never possesses an
exotic equation of state with the pressure exceeding the energy density.Comment: 1 page + Ref
Acoustics of tachyon Fermi gas
We consider a Fermi gas of free tachyons as a continuous medium and find
whether it satisfies the causality condition. There is no stable tachyon matter
with the particle density below critical value and the Fermi momentum
that depends on the tachyon mass . The pressure
and energy density cannot be arbitrary small, but the situation is
not forbidden. Existence of shock waves in tachyon gas is also discussed. At
low density the tachyon matter remains stable but no shock wave
do survive.Comment: 14 pages, 2 figures (color
Shock waves in superconducting cosmic strings: growth of current
Intrinsic equations of motion of superconducting cosmic string may admit
solutions in the shock-wave form that implies discontinuity of the current term
\chi. The hypersurface of discontinuity propagates at finite velocity
determined by finite increment \Delta \chi =\chi_+ -\chi_-. The current
increases \chi_+>\chi_- in stable shocks but transition between spacelike (\chi
>0) and timelike (\chi<0) currents is impossible.Comment: 13 pages, 3 figure
A Radio Determination of the Time of the New Moon
The detection of the New Moon at sunset is of importance to communities based
on the lunar calendar. This is traditionally undertaken with visual
observations. We propose a radio method which allows a higher visibility of the
Moon relative to the Sun and consequently gives us the ability to detect the
Moon much closer to the Sun than is the case of visual observation. We first
compare the relative brightness of the Moon and Sun over a range of possible
frequencies and find the range 5--100\,GHz to be suitable. The next
consideration is the atmospheric absorption/emission due to water vapour and
oxygen as a function of frequency. This is particularly important since the
relevant observations are near the horizon. We show that a frequency of GHz is optimal for this programme. We have designed and constructed a
telescope with a FWHM resolution of 0.6 and low sidelobes to
demonstrate the potential of this approach. At the time of the 21 May 2012 New
Moon the Sun/Moon brightness temperature ratio was in agreement
with predictions from the literature when combined with the observed sunspot
numbers for the day. The Moon would have been readily detectable at from the Sun. Our observations at 16\,hr\,36\,min UT indicated that
the Moon would have been at closest approach to the Sun 16\,hr\,25\,min
earlier; this was the annular solar eclipse of 00\,hr\,00\,min\,UT on 21 May
2012.Comment: 11 pages, 15 figures, accepted for publication in MNRA
Leiomyoma of the tunica albuginea, a case report of a rare tumour of the testis and review of the literature
BACKGROUND: Leiomyomas are benign tumours that originate from smooth muscles. They are often seen in the uterus, but also in the renal pelvis, bladder, spermatic cord, epididymis, prostate, scrotum or the glans penis. Leiomyomas of the tunica albuginea are extremely rare. CASE PRESENTATION: A 59-year-old white male has noted an asymptomatic tumour on the right side of his scrotal sac for several years. This tumour has increased slowly and caused local scrotal pain. An inguinal incision was performed, in which the hypoplastic testis, the epididymis and the tumour could be easily mobilized. Macroscopically the tumour showed a solid round nonencapsulated whorling cut surface. Histologically the diagnosis of a leiomyoma was made. CONCLUSION: We report here a very interesting and rare case of a leiomyoma of the tunica albuginea. Leiomyomas can be a possible differential diagnosis in this area. VIRTUAL SLIDES: http://www.diagnosticpathology.diagnomx.eu/vs/258509537853759
Forecasting Electricity Demand by Neural Networks and Definition of Inputs by Multi-Criteria Analysis
The planning of efficient policies based on forecasting electricity demand is essential to guarantee the continuity of energy supply for consumers. Some techniques for forecasting electricity demand have used specific procedures to define input variables, which can be particular to each case study. However, the definition of independent and casual variables is still an issue to be explored. There is a lack of models that could help the selection of independent variables, based on correlate criteria and level of importance integrated with artificial networks, which could directly impact the forecasting quality. This work presents a model that integrates a multi-criteria approach which provides the selection of relevant independent variables and artificial neural networks to forecast the electricity demand in countries. It provides to consider the particularities of each application. To demonstrate the applicability of the model a time series of electricity consumption from a southern region of Brazil was used. The dependent inputs used by the neural networks were selected using a traditional method called Wrapper. As a result of this application, with the multi-criteria ELECTRE I method was possible to recognize temperature and average evaporation as explanatory variables. When the variables selected by the multi-criteria approach were included in the predictive models, were observed more consistent results together with artificial neural networks, better than the traditional linear models. The Radial Basis Function Networks and Extreme Learning Machines stood out as potential techniques to be used integrated with a multi-criteria method to better perform the forecasting
Exponential and power law distribution of mass clusters in a (magnetic-like) deposition model of elongated grains in 2D piles
A generalized so called magnetically controlled ballistic rain-like
deposition (MBD) model of granular piles has been numerically investigated in
2D. The grains are taken to be elongated disks whence characterized by a
two-state scalar degree of freedom, called ''nip'', their interaction being
described through a Hamiltonian. Results are discussed in order to search for
the effect of nip flip (or grain rotation from vertical to horizontal and
conversely) probability in building a granular pile. The characteristics of
creation of + (or ) nip's clusters and clusters of holes (missing nips) are
analyzed. Two different cluster-mass regimes have been identified, through the
cluster-mass distribution function which can be exponential or have a power law
form depending on whether the nip flip (or grain rotation) probability is large
or small. Analytical forms of the exponent are empirically found in terms of
the Hamiltonian parameters.Comment: submitted to Int.J. Mod. Phys. C; 16 figures; 79 reference
Evaluating the implementation of the WHO Healthy Cities Programme across Germany (1999-2002)
The WHO Healthy Cities Project (1988) is a well-known example of the setting-based approach to health promotion. Developed as a framework for translating the key principles of the Ottawa Charter for Health Promotion (1986) into practice, it is best characterized as a process for successfully encouraging healthy public policy. In 2001, the German Healthy Cities Network (HCN) commissioned a survey of the 52 local Healthy Cities programme Coordinators (HCC) to monitor progress and identify strengths and weaknesses associated with its implementation. Most (90%; 47/52) HCC participated in the survey. Several positive aspects of the Health Cities Programmes (HCP) in Germany were identified: during the first 5 years, it expanded rapidly; project coordinators felt highly engaged, despite limited resources; a combination of traditional and innovative approaches was adopted and applauded; and almost 75% of HCC felt that their efforts had been beneficial. Nonetheless, the following shortcomings were identified: increased resources required; greater clarification of concepts and strategies at the local level; stronger commitment to the Nine-Point Programme of Action; greater integration within the national HCN and the local political administrative system (PAS); better programme documentation and evaluation. In conclusion, the HCN in Germany has expanded and developed since its inception 20 years ago. German HCP will only improve if professionalism and quality of local work are improved, particularly in terms of strengthening their influence on the local PAS and on public policies
Evaluation of selected characteristics in industrial hemp after phytohormonal treatment
Plant growth and development is significantly influenced by phytohormones \u2013 endogenous molecules present naturally in plants. The best known plant hormones are auxins and cytokinins. This study examined the possible effect of externally applied plant hormone analogues (growth regulators): 1-naphthyl acetic acid (NAA) and 6-benzyl aminopurine (BAP) on industrial fibre hemp (Cannabis sativa L., variety Bialobrzeskie). Plants were treated with three different concentrations of NAA (5, 10 and 20 mg/l) and three different concentrations of BAP (10, 25 and 50 mg/l). Morphological and physiological characteristics, such as apical dominance, shoot branching, fibre properties, and flavonoid content were evaluated. The chosen variety of hemp
had a significant response to exogenous application of growth regulators, as has been observed with other plant species. Most notably completely understood and controlled synthetic auxin treatment has a potential to increase the bark fibre yield of hemp
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