Masses and envelope binding energies of primary stars at the onset of a common envelope

We present basic properties of primary stars that initiate a common envelope (CE) in a binary, while on the giant branch. We use the population-synthesis code described in Politano et al. (2010) and follow the evolution of a population of binary stars up to the point where the primary fills its Roche lobe and initiates a CE. We then collect the properties of each system, in particular the donor mass and the binding energy of the donor's envelope, which are important for the treatment of a CE. We find that for most CEs, the donor mass is sufficiently low to define the core-envelope boundary reasonably well. We compute the envelope-structure parameter {\lambda_\mathrm{env}} from the binding energy and compare its distribution to typical assumptions that are made in population-synthesis codes. We conclude that {\lambda_\mathrm{env}} varies appreciably and that the assumption of a constant value for this parameter results in typical errors of 20--50%. In addition, such an assumption may well result in the implicit assumption of unintended and/or unphysical values for the CE parameter {\alpha_\mathrm{CE}}. Finally, we discuss accurate existing analytic fits for the envelope binding energy, which make these oversimplified assumptions for {\lambda_\mathrm{env}}, and the use of {\lambda_\mathrm{env}} in general, unnecessary.Comment: 6 pages, 3 figures, 1 table; to be published in the proceedings of the conference "Binary Star Evolution", in Mykonos, Greece, held in June 22-25, 201

Pilot’s Style of Learning and Thinking and Age-Related Declines in Visual Recall

This study examined the styles of learning and thinking and age-related visual recall performance of pilots. The study used the Style of Learning and Thinking (SOLAT) survey instrument to determine pilot\u27s learning preferences and compared pilot learning patterns to a control group of non-pilots. The study also examined possible decline in visual recall performance of pilots using a neuropsychological test, the Rey-Osterreich Complex Figure test (ROCF). Decline in visual recall performance of pilots can affect flight safety. There were 130 military pilots, 35 commercial aviation pilots, 26 general aviation pilots, and 57 non-pilot controls in the study

Analysis of Hazardous Material Incidents Reported to the Aviation Safety Reporting System

Hazardous and dangerous goods are often shipped by air on both passenger and cargo aircraft. These hazardous materials (HAZMAT), also known as dangerous goods (DG), pose a danger to flight safety, passengers, and airline personnel. This research explored how effective the Aviation Safety Reporting System (ASRS) is at identifying aviation related HAZMAT incidents. Early identification of HAZMAT trends using the ASRS data could lead to changes in aviation safety monitoring and reduce the likelihood of a HAZMAT event causing an incident. This study identified prevalent categories of hazardous material found in reported incidents. The study further identified that most of the HAZMAT incidents involved cargo being flown on passenger aircraft and that two-thirds of the incidents were discovered after take-off. Missing or incorrect documentation was identified in approximately half of the cases. Statistical analysis of the data indicated that HAZMAT paperwork errors correlated significantly with damage to an aircraft and that the source of the problem (passenger carry on, passenger checked, cargo) correlated significantly with where (climb-out, landing, ground, cruise) the problems occurred

On the Existence of Low-Luminosity Cataclysmic Variables Beyond the Orbital Period Minimum

Models of the present-day intrinsic population of cataclysmic variables predict that 99 per cent of these systems should be of short orbital period. The Galaxy is old enough that approx. 70 per cent of these stars will have already reached their orbital period minimum (approx. 80 min), and should be evolving back toward longer periods. Mass-transfer rates in these highly evolved binaries are predicted to be less or equal to 10(exp -11), leading to M(sub V) of approx. 10 or fainter, and the secondaries would be degenerate, brown dwarf-like stars. Recent observations of a group of low-luminosity dwarf novae (TOADS) provide observational evidence for systems with very low intrinsic M,. and possibly low-mass secondaries. We carry out population synthesis and evolution calculations for a range of assumed ages of the Galaxy in order to study P(sub orb) and M distributions for comparison with the TOAD observations. We speculate that at least some of the TOADs are the predicted very low- luminosity, post-period-minimum cataclysmic variables containing degenerate (brown dwarf-like) secondaries having masses between 0.02 and 0.06 M, and radii near 0.1 R., We show that these low-luminosity systems are additionally interesting in that they can be used to set a lower limit on the age of the Galaxy. The TOAD with the longest orbital period currently known (123 min), corresponds to a Galaxy age of at least 8.6 x 10(exp 9) yr

Characteristics of Helicopter Accidents Involving Male and Female Pilots

Studies examining aviation accidents have not found differences in accident rates by gender, though there may be gender differences in the types of accident. Baker, Lamb, Grabowski, and Rebok (2001) examined fixed-wing aviation accident rates of male and female private pilots and found that males were more likely to have accidents related to inattention or poor planning while female pilots were more likely to have accidents due to mishandling the aircraft. This research analyzed the National Transportation Safety Board’s aviation accident database system to examine the severity of injury and aircraft damage in rotary-wing (helicopter) accidents by gender. The data indicated that female helicopter pilots have slightly higher accident rates with higher aircraft damage and personnel injury rates at lower levels of training and experience, but have superior records as compared to male pilots at higher levels of experience. Overall, minimal differences in accident rates for helicopter pilots can be tied to gender differences

Differences in the Severity of General Aviation Accidents by Age: A Preliminary Examination

This research utilized the NTSB aviation accident and incident database system from 1982 to 2014 to examine differences in the severity of accidents by age for aviation accidents. Accidents were separated by commercial and general aviation (GA). There were 74,686 entries, after excluding home built aircraft, helicopters, and gliders, consisting of 7,203 commercial and 61,363 GA accidents. For commercial, male pilots made up 97.4%, (mean age = 41.75, (SD=10.88). Female pilots (2.6%), had a mean age of 43.51 (SD=9.71). Ages were significantly different, t(7009)=8.76, pSD=14.63). Damage to the aircraft and injury of crew/passengers as a function of pilot age was examined separately using ANOVA for commercial and GA. For commercial operation, damage levels of none, minor, substantial, and destroyed produced a significant difference by age, F(3, 7197)=40.558, pF(3,60302)=4.06, p=.007. There were significant differences between no damage and substantial (p=.001) and destroyed (p=.005) but no other levels. This study indicated that there are differences in the degree of damage related to aviation accidents based on age. Additional examination of the causes of accidents, and at what age the increase is observed, is needed to ensure aviation safety for aging pilots

Age Differences in Helicopter Accidents: A Preliminary Investigation

This study utilized the NTSB database from 2006 to 2016 to examine differences in severity of accidents by age for helicopter operations. There were 1023 cases included in the data (97.1% male and 2.9% female). The average age for helicopter pilots in the database was 47.00 years (SD=13.78). The average number of flying hours was 5447.98 (SD=6825.90, sk=1.982). An ANOVA was used to examine the effects of age on damage to the aircraft and injury to aircraft occupants. There was not a significant difference in pilot ages across the damage categories of none, minor, substantial, and destroyed, F(3,1019)=.763, p=.515, with average ages of 46.64, 46.04, 46.86, and 49.58 across the categories. There was a significant difference in age across injury categories of none, minor, serious, and fatal, F(3,1019)=7.549, p To examine further the apparent conundrum that injuries went up with age while damage did not, additional analyses were conducted looking particularly at helicopter pilots between 50 and 59 and 60 and 69. For the two groups, there was not a significant difference by age for damage or injury [F(3,234)=.784, p=.504; F(3,234)=.745, p=.526, F(3, 1880=1.395, p=.246, F(3, 188)=.173, p=.915 respectively]. Discounting reporting anomalies, when proportional damage was examined (for age \u3e60 pilots) 86.45% of aircraft sustained substantial damage; in the same age group, 95.31% of aircraft sustained substantial damage or destroyed resulting in 35.42% of those accidents involving serious injury or loss of life

Population Synthesis of Common Envelope Mergers: I. Giant Stars with Stellar or Substellar Companions

Using a population synthesis technique, we have calculated detailed models of the present-day field population of objects that have resulted from the merger of a giant primary and a main-sequence or brown dwarf secondary during common-envelope evolution. We used a grid of 116 stellar and 32 low-mass/brown dwarf models, a crude model of the merger process, and followed the angular momentum evolution of the binary orbit and the primary's rotation prior to merger, as well as the merged object's rotation after the merger. We find that present-day merged objects that are observable as giant stars or core-helium burning stars in our model population constitute between 0.24% and 0.33% of the initial population of ZAMS binaries, depending upon the input parameters chosen. The median projected rotational velocity of these merged objects is ~16 km/sec, an order of magnitude higher than the median projected rotational velocity in a model population of normal single stars calculated using the same stellar models and initial mass function. The masses of the merged objects are typically less than ~2 solar masses, with a median mass of 1.28 solar masses, which is slightly more than, but not significantly different from, their normal single star counterparts. The luminosities in our merged object population range from ~10-100 solar luminosities, with a strong peak in the luminosity distribution at ~60 solar luminosities, since the majority of the merged objects (57%) lie on the horizontal branch at the present epoch. The results of our population synthesis study are discussed in terms of possible observational counterparts either directly involving the high rotational velocity of the merger product or indirectly, via the effect of rotation on envelope abundances and on the amount and distribution of circumstellar matter.Comment: 16 pages, 12 figures, accepted for publication in the Astrophysical Journa

The Effect of Preoperative Recombinant Erythropoietin on Postoperative Hematocrit Level After Orthognathic Surgery

Compare the post-surgery red cell mass as indicated by hematocrit value of orthognathic surgery patients given iron supplementation and a single presurgery dose of erythropoietin alpha(EPO) and patients who did not receive either EPO or iron supplementation (NEPO)

The Formation of Cataclysmic Variables with Brown Dwarf Secondaries

The present-day formation of cataclysmic variables (CVs) with brown dwarf (BD) secondaries (0.013 M_sun < M_sec < 0.075 M_sun) is investigated using a population synthesis technique. Results from the latest, detailed models for BDs have been incorporated into the population synthesis code. For our models, we find that ZACVs with BD secondaries have orbital periods in the range 46 min to 2.5 hrs. We also find that ZACVs with BD secondaries comprise 18% of the total, present-day ZACV population. In addition, we find that 80% of ZACVs with BD secondaries have orbital periods < 78 minutes. This implies that 15% of the present-day ZACV population should have orbital periods shorter than the observed orbital period minimum for CVs. We also investigate the dependence of the present-day formation rate of CVs with BD secondaries on the assumed value of the common envelope efficiency parameter, alpha_CE, for three different assumed mass ratio distributions in ZAMS binaries. Surprisingly, we find that the common envelope process must be extremely inefficient (alpha_CE < 0.1) in order for CVs with BD secondaries not to be formed. Finally, we find that the progenitor binaries of ZACVs with BD secondaries have ZAMS orbital separations < 3 AU and ZAMS primary masses between ~1-10 M_sun, with ~75% of the primary masses less than ~1.6 M_sun. Interestingly, these ranges in orbital separation and primary mass place the majority of the progenitor binaries within the so-called ``brown dwarf desert.''Comment: preprint 27 pages 4 figures; to appear in ApJ April 1, 200