The Neutron Star Mass Distribution

In recent years, the number of pulsars with secure mass measurements has increased to a level that allows us to probe the underlying neutron star (NS) mass distribution in detail. We critically review the radio pulsar mass measurements. For the first time, we are able to analyze a sizable population of NSs with a flexible modeling approach that can effectively accommodate a skewed underlying distribution and asymmetric measurement errors. We find that NSs that have evolved through different evolutionary paths reflect distinctive signatures through dissimilar distribution peak and mass cutoff values. NSs in double neutron star and neutron star-white dwarf systems show consistent respective peaks at 1.33 Msun and 1.55 Msun suggesting significant mass accretion (delta m~0.22 Msun) has occurred during the spin-up phase. The width of the mass distribution implied by double NS systems is indicative of a tight initial mass function while the inferred mass range is significantly wider for NSs that have gone through recycling. We find a mass cutoff at ~2.1 Msun for NSs with white dwarf companions which establishes a firm lower bound for the maximum NS mass. This rules out the majority of strange quark and soft equation of state models as viable configurations for NS matter. The lack of truncation close to the maximum mass cutoff along with the skewed nature of the inferred mass distribution both enforce the suggestion that the 2.1 Msun limit is set by evolutionary constraints rather than nuclear physics or general relativity, and the existence of rare super-massive NSs is possible.Comment: 13 pages, 4 figures, 2 tables. ApJ in press. A completely new and more flexible statistical model applied. Astrophysical results remained same as arXiv:1011.429

Flow Trees: A Lower Bound Computation Tool with Applications to Rearrangeable Multihop Lightwave Network Optimization

This paper presents a new method for computing the lower bounds for multihop network design problems which is particularly well suited to optical networks. More specifically, given N stations each with d transceivers and pairwise average traffic values of the stations, the method provides a lower bound for the combined problem of finding optimum (i) allocation of wavelengths to the stations to determine a configuration, and (ii) routing of the traffic on this configuration while minimizing congestion - defined as the maximum flow assigned on any link. The lower bounds can be computed in time polynomial in the network size. Consequently, the results in this work yield a tool which can be used in (i) evaluating the quality of heuristic design algorithms, and (ii) determining a termination criteria during minimization. The lower bound computation is based on first building flow trees to find a lower bound on the total flow, and then distributing the total flow over the links to minimize the congestion

Logical Embeddings for Minimum Congestion Routing in Lightwave Networks

The problem considered in this paper is motivated by the independence between logical and physical topology in Wavelength Division Multiplexing WDM based local and metropolitan lightwave networks. This paper suggests logical embeddings of digraphs into multihop lightwave networks to maximize the throughput under nonuniform traffic conditions. Defining congestion as the maximum flow carried on any link, two perturbation heuristics are presented to find a good logical embedding on which the routing problem is solved with minimum congestion. A constructive proof for a lower bound of the problem is given, and obtaining an optimal solution for integral routing is shown to be NP-Complete. The performance of the heuristics is empirically analyzed on various traffic models. Simulation results show that our heuristics perform on the average from a computed lower bound Since this lower bound is not quite tight we suspect that the actual performance is better In addition we show that 5%-20% performance improvements can be obtained over the previous work

Do all millisecond pulsars share a common heritage?

The discovery of millisecond pulsations from neutron stars in low mass X-ray binary (LMXB) systems has substantiated the theoretical prediction that links millisecond radio pulsars (MSRPs) and LMXBs. Since then, the process that produces millisecond radio pulsars from LMXBs, followed by spin-down due to dipole radiation has been conceived as the 'standard evolution' of millisecond pulsars. However, the question whether all the observed millisecond radio pulsars could be produced by LMXBs has not been quantitatively addressed until now. The standard evolutionary process produces millisecond pulsars with periods (P) and spin-down rates (Pdot) that are not entirely independent. The possible P-Pdot values that millisecond radio pulsars can attain are jointly constrained. In order to test whether the observed millisecond radio pulsars are the unequivocal descendants of millisecond X-ray pulsars (MSXP), we have produced a probability map that represents the expected distribution of millisecond radio pulsars for the standard model. We show with more than 95 % confidence that the fastest spinning millisecond radio pulsars with high magnetic fields, e.g. PSR B1937+21, cannot be produced by the observed millisecond X-ray pulsars within the framework of the standard model.Comment: Full resolution color figures available at: http://www.kiziltan.org/research.html. To appear in the American Institute of Physics (AIP) proceedings, 8 pages, 2 figures, 1 tabl

Privatization and regulation in Turkish telecommunications

Version of RecordThe importance of efficient workings of network industries and the markets in which they operate has long been recognized in the literature. In a parallel fashion, policy makers around the world initiated various restructuring efforts focusing on these sectors. However, the issues of privatization and much needed subsequent regulatory framework face considerable challenges in developing countries. Both political opposition and difficulties encountered in the process of privatization caused major delays in overall privatization and restructuring efforts of these countries. This paper focuses on the telecommunications sector and the Turk Telekom case, in particular, assessing the prospects for its much-debated divestiture, evaluating the company specifics and subsequent regulatory agenda. In doing that, it emphasizes the current "telecom meltdown" in international markets, and compares telecommunications privatizations of various nations. Additionally, the study reviews major regulatory methods and draws on some recommendations for policy makers in the light of the U.S experience in this sector.Aybar, C. B., Guney, S., & Suel, H. (2001, March). Privatization and regulation in Turkish telecommunications: A critical assessment (Working Paper). Manchester, NH: Southern New Hampshire University. Retrieved from http://academicarchive.snhu.ed

Assessment of fetal adrenal gland enlargement in term and preterm labor cases

Background: The objective of this study was to compare the Fetal Zone Depth (FZD) of fetal adrenal gland in term and preterm labor cases.  Methods: Twenty nine preterm pregnant women at 29-36 weeks of gestation with single pregnancy admitted with the clinical diagnosis of preterm labor and the comparison group of 33 pregnant women at 37-40 weeks with term pregnancy were included in this study. FZD and Total Gland Depth (TGD) of fetal adrenal gland of the entire fetuses in sagittal plane were ultrasonographically measured and FZD/TGD ratios were calculated. Demographic and clinical features, laboratory findings and fetal adrenal gland FZD/TGD ratios were compared between the two groups.Results: No difference was found between the two groups in respect of age, number of pregnancies and delivery method (P >0.05); yet preterm birth history and duration of hospital stay were higher in preterm group (P <0.05). Fetal adrenal gland FZD/TGD ratio was statistically significantly higher in preterm group compared to the term group (55.4% ± 4.9 vs. 47.7% ± 5.6; P <0.001).Conclusion: The growth in FZ as a fetal adaptation mechanism in increased fetal stress in preterm labor cases was at a significant level. Once supported by more comprehensive studies, we think that this result would be beneficial in the prediction of preterm labor in clinical practice.

The distance to the SNR CTB109 deduced from its environment

We conducted a study of the environment around the supernova remnant CTB109. We found that the SNR is part of a large complex of HII regions extending over an area of 400 pc along the Galactic plane at a distance of about 3 kpc at the closer edge of the Perseus spiral arm. At this distance CTB109 has a diameter of about 24 pc. We demonstrated that including spiral shocks in the distance estimation is an ultimate requirement to determine reliable distances to objects located in the Perseus arm. The most likely explanation for the high concentration of HII regions and SNRs is that the star formation in this part of the Perseus arm is triggered by the spiral shock.Comment: 6 pages, 6 figures. accepted for publication in the Astrophysical Journa

Koncentracije serumskog prokalcitonina i C-reaktivnog proteina u pasa s degenerativnom bolešću mitralnog zaliska i infektivnim endokarditisom

This study aimed to investigate the clinical significance of serum C-reactive protein (CRP) and procalcitonin (PCT) concentrations in dogs with degenerative mitral valve disease (DMVD) and infective endocarditis. It also aimed to evaluate whether there is a relationship between the degree of disease and serum PCT and CRP concentrations. A total of 100 dogs with MVD were prospectively recruited into the study. According to clinical/laboratory signs and echocardiography, the dogs were divided into infective and degenerative groups. The degenerative group was also classified into four stages based on the American College of Veterinary Internal Medicine (ACVIM) guidelines (Stages A-D). Serum PCT and CRP concentrations were determined with dog-specific commercial test kits. The serum CRP (P<0.05) and PCT (P<0.001) concentrations in the infective group were significantly higher than the degenerative group. In the degenerative group, the serum CRP concentration of stage D dogs was significantly higher than the other stages (P<0.001), and the degree of disease correlated significantly positively with serum CRP concentration (r=0.531 P=0.000). In conclusion, serum CRP and PCT concentrations may aid traditional diagnostic techniques to differentiate infective and degenerative mitral valve disease. This study also demonstrated that serum CRP concentrations were elevated in Stage D dogs, and that there is a positive correlation between the degree of disease and serum CRP concentration. This can be useful in determining the severity of the inflammatory state in dogs with DMVD.Cilj rada bio je istražiti kliničku važnost serumskih koncentracija C-reaktivnog proteina (CRP) i prokalcitonina (PCT) u pasa s degenerativnom bolešću mitralnog zaliska (DMVD) i infektivnim endokarditisom. Također, cilj je bio i procijeniti postoji li povezanost između stupnja bolesti i serumskih koncentracija PCT-a i CRP-a. U prospektivno istraživanje uključeno je ukupno je 100 pasa s MVD-om. Prema kliničko laboratorijskim znakovima i ehokardiografiji psi su podijeljeni u skupinu s infektivnom i skupinu s degenerativnom bolešću. Psi s degenerativnom bolešću razvrstani su u četiri stadija (A-D) prema smjernicama American College of Veterinary Internal Medicine (ACVIM). Koncentracije serumskog PCT-a i CRP-a određene su komercijalnim testnim setovima specifičnima za pse. Koncentracije serumskog CRP-a i PCT-a u skupini pasa s infektivnom bolešću bile su znakovito više (P<0,05 i P<0,001) nego one u skupini pasa s degenerativnom bolešću. U skupini s degenerativnom bolešću serumske koncentracije CRP-a u pasa sa stadijem D bile su znakovito više nego u pasa s ostalim stadijima (P<0,001). Stupanj bolesti bio je u znakovitoj pozitivnoj korelaciji sa serumskim koncentracijama CRP-a (r = 0,531, P=0,000). Zaključno, serumske koncentracije CRP-a i PCT-a mogu pomoći tradicionalnim dijagnostičkim metodama u razlikovanju infektivne i degenerativne bolesti mitralnog zaliska. Istraživanje je pokazalo i povišene serumske koncentracije CRP-a u pasa sa stadijem D te pozitivnu korelaciju između stupnja bolesti i koncentracije CRP-a. Navedeno može biti korisno pri procjeni težine upalnog stanja u pasa s DMVD-om

A chemical genetic approach reveals distinct EphB signaling mechanisms during brain development.

EphB receptor tyrosine kinases control multiple steps in nervous system development. However, it remains unclear whether EphBs regulate these different developmental processes directly or indirectly. In addition, given that EphBs signal through multiple mechanisms, it has been challenging to define which signaling functions of EphBs regulate particular developmental events. To address these issues, we engineered triple knock-in mice in which the kinase activity of three neuronally expressed EphBs can be rapidly, reversibly and specifically blocked. We found that the tyrosine kinase activity of EphBs was required for axon guidance in vivo. In contrast, EphB-mediated synaptogenesis occurred normally when the kinase activity of EphBs was inhibited, suggesting that EphBs mediate synapse development by an EphB tyrosine kinase-independent mechanism. Taken together, our data indicate that EphBs control axon guidance and synaptogenesis by distinct mechanisms and provide a new mouse model for dissecting EphB function in development and disease

Physicians' perception of childhood asthma in Turkey: more appropriate practice among female physicians

<p>Abstract</p> <p>Background</p> <p>Low levels of asthma control worldwide point to the possibility of sub-optimal management; therefore, documentation of physicians' perception is critical for future interventions. Our aim was to examine self-reported management abilities of Turkish physicians dealing with children with asthma, document the factors affecting appropriate decisions and compare the results with those of a previous survey.</p> <p>Methods</p> <p>Physicians were surveyed via a questionnaire aimed to document self-perceived asthma knowledge and attitudes in asthma management.</p> <p>Results</p> <p>The majority of physicians were male (63%) and examined 234 ± 9 patients per week. Infrequent use of objective parameters in asthma diagnosis and attack severity assessment was reported and most preferred nebulized corticosteroids to the systemic form in acute asthma. Even though self-perceived overall asthma knowledge did not differ between genders (p = 0.098), male physicians scored higher than females for inhaled steroids for acute asthma (2.8 ± 0.12 vs 2.17 ± 0.2, respectively, p = 0.007), while female physicians recorded more frequent use of inhaled steroids for chronic asthma (3.72 ± 0.08 vs 3.43 ± 0.07, respectively, p = 0.006). Female physicians' scoring for "symptom control" as the main aim of asthma management was higher than that of their male counterparts (3.88 ± 0.04 vs 3.65 ± 0.06, respectively, p = 0.002).</p> <p>Conclusion</p> <p>Although there were some discrepancies between guidelines and clinical practice, most applications of Turkish physicians dealing with children with asthma were appropriate. Interestingly, when scores of female versus male physicians were compared, it can be suggested that female physicians have a more appropriate perception of asthma, indicating a significant contribution of gender-related factors in clinical attitudes and beliefs.</p