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Background Normal C-reactive protein (CRP) and white cell count (WCC) are often used to exclude a diagnosis of acute appendicitis in the Emergency Department (ED). Retrospective review of 281 adult patients with acute appendicitis was performed to study the incidence of normal CRP and WCC on admission and examine any possible predisposing factors. Method Retrospective analysis of patient clinical records yielded CRP, WCC, operative diagnosis, time of symptom onset, imaging results and history and examination features. Case-control analysis was performed with patients with normal CRP and WCC considered the case group and those with raised CRP or WCC considered controls. Groups were compared using Mann-Whitney U-test and chi-squared analysis. Results Of 281 consecutive patients with histologically proven appendicitis, 24 (8.54%) had normal CRP and WCC on presentation to ED. There were no significant differences in age, sex or time to blood collection between groups. Three patients had normal WCC and CRP and an Alvarado score of 4 or less on presentation. Three patients had persistently normal CRP and WCC on repeated testing. There was a trend towards earlier presentation in patients with normal CRP and WCC with 75.0% versus 58.4% presenting within 24 h of symptom onset (OR 2.14, P = 0.112). Conclusion Acute appendicitis remains diagnostically challenging and cannot be excluded on the basis of normal CRP and WCC. Serial clinical and biochemical assessment is warranted in patients with acute abdominal pain, particularly in those presenting early after symptom onset.

The possibility of meteoroid impact is one of the main threats to the interplanetary missions. Although the meteoroids in the interplanetary space have very small masses, their velocities are extremely large and can produce highly energetic impacts. In this paper, a specific method to analyze the meteoroid environment on the transfer trajectories to Mars has been developed, by determination of the closest approach situation for a large sample of meteoroid orbits. This allows to analyze, not only the integral flux of meteoroids on the spacecraft surfaces, but also the specific kinematics for every single approach and the distributions of important variables such as relative velocity and its projections on specific directions such as instantaneous directions to Mars, Earth, Sun and apex. The obtained results give the quantitative and qualitative estimate of these variables which are separated for different populations of interplanetary meteoroids. The most exposed parts of the spacecraft on the Hohmann transfer to Mars are directed toward Mars, apex and anti-Earth point while the Sun and anti-Sun directions are symmetrically threatened. This gives the frame for the mission design and impact risk assessment and for the development of mathematical models of the behavior of the new spacecraft protection materials under impact loading and also for their experimental examination.

The phenomena like high eccentricity of Martian orbit, obliquity of the orbital plane and close alignment of the winter solstice and the orbital perihelion, separately or together can significantly alter not only the level of some Martian atmospheric parameters but also the characteristics of its diurnal and seasonal cycle. Considering that entry, descent and landing (EDL) sequence is mainly driven by the density profile of the atmosphere and aerodynamic characteristic of the entry vehicle. We have performed the analysis of the influence of the seasonal cycles of the atmospheric parameters on EDL profiles by using Mars Global Reference Atmospheric Model (Mars-GRAM). Since the height of the deployment of the parachute and the time passed from the deployment to propulsion firing (descent time) are of crucial importance for safe landing and the achievable landing site elevation we paid special attention to the influence of the areocentric longitude of the Sun (Ls) on these variables. We have found that these variables have periodic variability with respect to Ls and can be very well approximated with a sine wave function whose mean value depends only on the landing site elevation while the amplitudes and phases depend only on the landing site latitude. The amplitudes exhibit behavior which is symmetric with respect to the latitude but the symmetry is shifted from the equator to the northern mid-tropics. We have also noticed that the strong temperature inversions which are usual for middle and higher northern latitudes while Mars is around its orbital perihelion significantly alter the descent time without influencing the height of the parachute deployment. At last, we applied our model to determine the dependence of the accessible landing region on Ls and found that this region reaches maximum when Mars is around the orbital perihelion and can vary 50° in latitude throughout the Martian year.

Normal C-reactive protein (CRP) and white cell count (WCC) are often used to exclude a diagnosis of acute appendicitis in the Emergency Department (ED). Retrospective review of 281 adult patients with acute appendicitis was performed to study the incidence of normal CRP and WCC on admission and examine any possible predisposing factors.Retrospective analysis of patient clinical records yielded CRP, WCC, operative diagnosis, time of symptom onset, imaging results and history and examination features. Case-control analysis was performed with patients with normal CRP and WCC considered the case group and those with raised CRP or WCC considered controls. Groups were compared using Mann-Whitney U-test and chi-squared analysis.Of 281 consecutive patients with histologically proven appendicitis, 24 (8.54%) had normal CRP and WCC on presentation to ED. There were no significant differences in age, sex or time to blood collection between groups. Three patients had normal WCC and CRP and an Alvarado score of 4 or less on presentation. Three patients had persistently normal CRP and WCC on repeated testing. There was a trend towards earlier presentation in patients with normal CRP and WCC with 75.0% versus 58.4% presenting within 24 h of symptom onset (OR 2.14, P = 0.112).Acute appendicitis remains diagnostically challenging and cannot be excluded on the basis of normal CRP and WCC. Serial clinical and biochemical assessment is warranted in patients with acute abdominal pain, particularly in those presenting early after symptom onset.

Our main aim is to apply the theory of regularly varying functions to the asymptotical analysis at infinity of solutions of Friedmann cosmological equations. A new constant $\Gamma$ is introduced related to the Friedmann cosmological equations. Determining the values of $\Gamma$ we obtain the asymptotical behavior of the solutions, i.e. of the expansion scale factor $a(t)$ of a universe. The instance $\Gamma < 1/4$ is appropriate for both cases, the spatially flat and open universe, and gives a sufficient and necessary condition for the solutions to be regularly varying. This property of Friedmann equations is formulated as the generalized power law principle. From the theory of regular variation it follows that the solutions under usual assumptions include a multiplicative term which is a slowly varying function., Comment: 26 pages, 2 figures

This paper presents the distributions of the positions of the Minimal Orbit Intersection Distances (MOID) among three subgroups of the Near Earth Asteroids (NEAs). This includes 683 Atens, 4185 Apollos and 3538 Amors which makes over 15 millions combinations of the pairs of orbits. The results which are obtained in this analysis show very interesting distributions of positions of the MOIDs and circumstances of close approaches of the asteroids and emphasize influence of different orbital elements on these distributions.

We present an extended analysis of the relation between radio surface brightness and diameter -- the so-called $\Sigma-D$ relation for planetary nebulae (PNe). We revise our previous derivation of the theoretical $\Sigma-D$ relation for the evolution of bremsstrahlung surface brightness in order to include the influence of the fast wind from the central star. Different theoretical forms are derived: $\Sigma \propto D^{-1}$ for the first and second phases of evolution and $\Sigma\propto D^{-3}$ for the final stage of evolution. Also, we analyzed several different Galactic PN samples. All samples are influenced by severe selection effects, but Malmquist bias seems to be less influential here than in the supernova remnant (SNR) samples. We derived empirical $\Sigma-D$ relations for 27 sample sets using 6 updated PN papers from which an additional 21 new sets were extracted. Twenty four of these have a trivial form of $\beta \approx 2$. However, we obtain one empirical $\Sigma-D$ relation that may be useful for determining distances to PNe. This relation is obtained by extracting a recent nearby (< 1 kpc) Galactic PN sample.

Improved constants of the total density TD-88 model for the Earth's neutral thermosphere are calculated. The model is fully functional within the height range of 200 to 500 km, with fixed values of the mean solar flux and geomagnetic index. The control data of the atmospheric air density are derived from the aeronomical NRLMSISE-00 model which was used as the reference one. The upgraded TD-88, named TD-88Up, model is obtained by the extended LSQ method with varying all model parameters.

A complex software for preparation and treatment of astro photographic plates and double-star observations recorded with CCD cameras is developed. The preparation interface contains a catalogue base for the choice of observation objects and an interface for bringing into accordance the telescope and CCD camera performance with the assumptions of the postprocessor interface. The processing is based on the original development of image gradient removing software and classical FFT method and autocorrelation. The software has been tested on several theoretical and real images of double stars.

In this paper we examine air densities derived from our realization of aeronomic atmosphere models based on accelerometer measurements from satellites in a low Earth's orbit (LEO). Using the adapted algorithms we derive comparison parameters. The first results concerning the adjustment of the aeronomic models to the total-density model are given.

Using the method of multi-composing of ordinates we have identified in Earth?s rotation a long-periodic term with a period similar to the relaxation time of Chandler nutation. There was not enough information to assess its origin. We demonstrate that the method can be used even in the case when the data time span is comparable to the period of harmonic component.

In this paper we describe a method of plain and multi composing of ordinates to define spectral filters. We apply the method to the simulated equidistant observations, and we find that the suitable filters are easy to construct and apply.

The chromatographic behavior of mixed 1,2,4,5-tetraoxanes, cholic and deoxycholic acid derivatives with distinct biological activity, was examined by high-performance thin-layer chromatography in order to correlate their structure and retention. Chromatographic systems were consisted of RP-18 or CN-silica as stationary phase, and binary mixtures of water with methanol, dioxane or acetone as mobile phase. Based on the respective retentions, the lipophilicity of the investigated compounds was determined. Multiple linear regression and partial least squares have been used to select variables that best describe the behavior of the investigated compounds in chromatographic systems and to quantify influences of most important parameters. The validation and cross-validation of the QSRR model suggest its applicability for prediction and understanding of retention of congeners. The models indicate the importance of nonpolar properties of the solutes and their ability for hydrophobic interactions, as well as the importance of proton donating abilities, hydrophilic and,pi interactions pointing out on that way the possible separation mechanism in the studied chromatographic systems. Observed correlations between structure and biological activity of mixed 1,2,4,5-tetraoxanes, indicate that the antimalarial activity against W2 and D6 Plasmodium falciparum strains, is governed by hydrophobic feature (measured with lipophilicity parameter), hydrophilic feature (measured with HLB, %HS, HB and HBA descriptors), and electronic feature (HOMO). This is the peer-reviewed version of the article: S. Segan, N. Terzic-Jovanovic, D. Milojkovic-Opsenica, J. Trifkovic, B. Solaja, D. Opsenica, Correlation study of retention data and antimalarial activity of 1,2,4,5-mixed tetraoxanes with their molecular structure descriptors and LSER parameters, Journal of Pharmaceutical and Biomedical Analysis (2014), [http://dx.doi.org/10.1016/j.jpba.2014.04.029] [http://cer.ihtm.bg.ac.rs/handle/123456789/1599]

Astronomical society "Magellanic cloud" was founded on May 16, 2001 in the town of Prokuplje, Serbia, by A. Simonovic, A. Valjarevic, then students of geography at the University of Pristina, Z. Mijajlovic professor of mathematics, S. Segan, professor of astronomy, both of the University of Belgrade. In this paper we present. the activities of the Society in the popularization of astronomy and mathematics in Prokuplje and its vicinity. Also, the role of the Society in building the Astronomical station of the Astronomical observatory of Belgrade at. the mountain Vidojevica close to Prokuplje is described.