Light Twin Research Articles

Birth weight and body composition in young adult men--a prospective twin study.

To evaluate the association between birth weight and adult body composition in twins, controlling for maternal and genetic influences. Twins were randomly selected from the East Flanders Prospective Twin Survey, a population-based historic twin cohort. Male members of 229 twin pairs between 18 and 34 y of age who participated in the Prenatal Programming Twin Study. Adult body mass, height, BMI, lean body mass, sum of skinfolds and waist-to-hip-ratio. Lean body mass, sum of skinfolds and waist-to-hip-ratio were also adjusted for body mass. Intra-pair difference in adult anthropometric measures between the heaviest and the lightest twin at birth. Per kg increase in birth weight, body mass (4.2 kg), height (3.3 cm), lean body mass (3.1 kg) and to a lesser extent BMI (0.49 kg/m(2)) increased, whereas waist-to-hip-ratio (-1.4%) and sum of skinfolds (-0.11 s.d.) decreased, when adjusted for body mass. In a pair-wise analysis, the heavier twin at birth was taller and heavier as an adult, but, when adjusted for body mass, he had a lower waist-to-hip-ratio, less subcutaneous fat, and more lean body mass, compared to his lighter sib. Intra-pair difference in body composition was associated with intra-pair birth weight difference in monozygotic and dizygotic twins. An adverse intra-uterine environment, as measured by birth weight, is associated with more subcutaneous and abdominal fat and less lean body mass in adulthood. This association is independent of maternal and genetic influences. However, we cannot exclude the existence of genes that act on both birth weight and adult body composition.

Modelling, Control and Simulation OD a Light Twin-Engine Aircraft

At the Aerospace Laboratories of the Forlì (FO) branch of the University of Bologna a DGNSS Instrument Approach System (called FO-DIAS) is being implemented: this work will provide the overall simulation system autopilot that will be integrated with the Navigation System on developement. The aircraft considered is a light twin engine aircraft (PIPER PA-30 B TURBO) property of the University, located in the Hangar of the Departments of Aerospace and Mechanical Engineering of Forlì.The research has been divided into three parts:a) the determination of the aircraft dynamics mathematical model;b) the aircraft autopilot project;c) the simulation of the overall system.The aircraft dynamic model is based on the linearization and decoupling of the equations system: the parameters necessary to implement the model with this approach are the aircraft stability and control derivatives, both longitudinal and lateral-directional. These values are known from a windtunnel investigation of the full-scale aircraft. An analytical approach to evaluate theese coefficients is being developed.The project of the autopilot is still limited to the approach phase and in the future it will be developed for the holding phase too. The autopilot has a PID standard structure with a parameters tuning new approach developed by our team and for the next holding phase autopilot will be implemented predictive PID with gain scheduling approach. The overall simulation system will be developed with the Matlab Simulink Toolbox of MathWorks Inc.

Recent Progress in Quantum Optics. Generation of Bright Squeezed Light and Quantum-Correlated Twin Photon Beams Using a Semimonolithic Optical Parametric Oscillator.

We have generated bright squeezed light and quantum-correlated twin photon beams by using a cw semimonolithic KTP Optical Parametric Oscillator (OPO), which exhibits a low oscillation threshold and is capable of oscillating even in the free-running (no external-feedback) condition. The pump beam reflected by the OPO, after a cascading nonlinearity process in the crystal, appears as bright squeezed light. The squeezing observed on the reflected pump beam from the semimonolithic OPO was 30% (inferred squeezing: 48%). The signal and idler beams generated by the optical parametric oscillator are highly quantum-correlated twin photon beams. Since the squeezing property of the intensity difference between the twin photonbeams is robust in the condition where the two fields are balanced, the squeezing can be observed even in the freerunning condition of the OPO. This intensity-difference squeezing observed between the twin photon beams from the free-running semimonolithic OPO was 70% (inferred squeezing: 87%).

Association between birth weight and adult blood pressure in twins: historical cohort study

Objectives: To evaluate the associations in twins between within pair differences in birth weight and subsequent blood pressures as adults thereby removing the impact of potential parental confounding variables.Design: Historical...

Analog Track Angle Error Displays Improve Simulated GPS Approach Performance

Pilots flying non-precision instrument approaches traditionally rely on a course deviation indicator (CDI) analog display of cross track error (XTE) information. The new generation of GPS based area navigation (RNAV) receivers can also compute accurate track angle error (TAE). Does display of supplementary TAE information improve intercept and tracking performance? Six pilots each flew 20 approaches in a light twin simulator to evaluate 3 different TAE/XTE display formats, in comparison to a conventional receiver CDI display and a more centrally located Horizontal Situation Indicator (HSI). Statistically significant performance improvements were seen in several phases of the approach when using the supplementary TAE information. Analog was preferred over numeric format. However, the advantage was offset by the need to widen the pilot's instrument scan to include the receiver display. Pilots found TAE helpful in establishing intercepts and the appropriate wind correction angle. Findings support the recent FAA TSO-C129 requirement that XTE be presented in the pilot's primary field of view, and the recommendation that avionics manufacturers include supplementary analog TAE display capability.

Pilot Performance and Workload Using Simulated GPS Track Angle Error Displays

The effect on simulated GPS instrument approach performance and workload resulting from the addition of Track Angle Error (TAE) information to cockpit RNAV receiver displays in explicit analog form was studied experimentally (5 display formats, 6 pilots, 20 approaches each) in a Frasca 242 light twin aircraft simulator. Inter subject differences in ability to use the displays were found, but sliding and tilting pointer TAE formats significantly improved intercept and tracking performance measures. Detennination of wind correction angle was simplified. Workload scores were not significantly influenced by display format, but depended on approach geometry and phase.

Placental pathology in discordant twins

The aim of this study was to evaluate placental abnormalities in relation to birth weight discordance in dichorionic and monochorionic twins. The maternal charts and placental abnormalities of 147 structurally normal twin pairs with cords labeled at delivery were reviewed. The placental weight belonging to each twin was determined by measuring the length, width, and thickness in each of the two placental disks. Placental weight, chorionicity, infarction, abruptio placentae, decidual vascular abnormality, villous fibrosis and hypovascularity, chronic villitis, and intraplacental thrombi were also assessed. Birth weight was discordant if > or = 20%. The data were analyzed with chi 2 and analysis of variance after log transformation of skewed discordancy values. Of the 147 twin pairs, 99 were dichorionic and 48 monochorionic. Placental weights were known for 91 dichorionic and 40 monochorionic twins. Of the lighter cotwins in dichorionic twin pairs 36.3% (33/91) belonged to the heavier placenta, 49.5% (45/91) belonged to the lighter placenta, and 14.3% (13/91) had an equal share of the placental weight with the heavier sibling (p < 0.05). In 42.4% (42/99) the lighter dichorionic twin had more placental lesions than the heavier twin, in 38.4% (38/99) the same number of lesions were present in both placentas, and in 19.2% (19/99) the heavier twin had more placental lesions. There was linear correlation between percent discordance and number of placental lesions in the lighter twin. In dichorionic twins 18 of the 99 (18.1%) were discordant. In 77.8% (14/18) the lighter twin had more placental lesions than the heavier twin, in 16.7% (3/18) the number of lesions was the same in both, and in 5.6% (1/18) the heavier twin had one more lesion than the lighter twin (p < 0.05). In monochorionic twins, regardless of birth weight discordance, no differences in placental abnormalities were observed. In dichorionic twins significant birth weight discordance was attributable not to differences in placental weight but to a greater number of placental lesions in the lighter twin than in the heavier twin (p < 0.05). This did not hold true for monochorionic twins.

The Effect of Low Blood Alcohol Levels on Pilot Performance in a Series of Simulated Approach and Landing Trials

Eight experienced pilots flew a series of approaches and landings in a simulator with the characteristics of a general aviation light twin. One half of the subjects were under the influence of low blood alcohol levels (mean = 11 mg%). Subjects in the alcohol condition showed significant deteriorations in their performance, as measured by deviations from the optimum approach speed or the optimum glideslope, when performing an instrument approach or when performing an asymmetric approach. The results are discussed with respect to the Federal Aviation Administration regulations concerning drinking and flying.

Composite Developments in Aircraft Structures — Part 3

Space limitations preclude more than a brief reference to other important developments in composites but several must be mentioned, the Bell‐Boeing V‐22 Osprey tilt‐rotor aircraft (Fig. 34), the Westland Agusta EH 101 Merlin helicopter (Fig. 35) and the MBB BO108 light twin helicopter (Fig. 36) share the need for the lowest possible structural weight and the maximum fatigue life of blades, consequently composites are widely used in these aircraft. Westland have, of course, achieved a high reputation with their advanced BERP rotor blades with an aerodynamic form said to be incapable of economic production in metal. Fitted with the new blades a Lynx helicopter established a world speed record for helicopters of over 216 knots in 1986.

Performance of Polypay, Coopworth, and crossbred ewes: I. Reproduction and lamb production1

Six ewe genotypes, generated by mating Coopworth (C), Polypay (P), and Suffolk (S) rams to Polypay and Coopworth-type (Ct) ewes, were exposed to Hampshire rams for spring lambing from 1986 through 1990. Data from 1,092 exposures and 1,044 resultant lambings were used to analyze reproductive traits and lamb growth rates. Overall conception rate averaged 95% and ranged from 93% for S x Ct ewes to 97% for P x Ct ewes. Mean litter size at birth averaged 1.63 and ranged from 1.45 for C x C ewes to 1.75 for S x P ewes. Ewes from P dams had higher mean litter size (P less than .01) than those from Ct dams (1.73 vs 1.54), but differences between sire breeds were not significant. Incidence of lambing assistance was similar for ewes producing single or multiple lambs. Lamb birth weight influenced the level of assistance rendered to single-bearing but not to multiple-bearing ewes. Lambing assistance was not related to lamb survival, probably because the high surveillance level minimized trauma before assistance was rendered. Incidence of required assistance declined over subsequent parities. Lamb birth weights were affected by ewe genotype and increased with increasing ewe age. Survival of single-born lambs averaged 94% and was not affected by dam genotype. Survival of twins averaged 85%, ranging from 79% for lambs from S x Ct ewes to 89% for lambs from P x P ewes. Suffolk-sired ewes produced the heaviest mean birth and weaning weights for both singles and twins. Coopworth-sired ewes weaned heavier single lambs but lighter twins than P-sired ewes.

MDX: New light twin is operator designed

Adjuvant chemotherapy (AC) is associated with improved survival following resection of pancreatic adenocarcinoma but is frequently delayed or deferred due to perioperative complications or patient deconditioning. The aim of this study was to assess impact of delayed AC on overall survival after pancreaticoduodenectomy for pancreatic head adenocarcinoma.Patients with stage I-III pancreatic head adenocarcinoma in the 2006–2015 National Cancer Database were grouped by timing of AC (<6-weeks, 6–12-weeks, and 12–24-weeks). Overall survival was compared using Cox proportional hazard models adjusting for patient, tumor, and hospital factors. Subgroup analyses were conducted to assess the impact of comorbidities, readmission or extended hospital stay, and receipt of single- versus multi-agent chemotherapy.Of 13438 patients, 4552 (33.9%) received no AC, 2112 (15.7%) received AC <6-weeks following resection, 5580 (41.5%) within 6–12 weeks, and 1194 (8.9%) within 12–24 weeks. AC was associated with improved overall survival (adjusted hazard ratio [HR] <6-weeks: 0.765, 6–12-weeks: 0.744, and 12–24-weeks: 0.736 (p < 0.001)). This survival advantage persisted for patients with comorbidities, those with postoperative complications, and in those receiving single- or multi-agent regimens.For patients with stage I-III pancreatic adenocarcinoma, receipt of AC is associated with improved overall survival, even if delayed up to 24-weeks.

Optimized Engine out Procedures For Multi Engine Airplanes

This investigation examined hazards associated with asymmetric thrust, engine out flying in twin engine airplanes at low speeds and low altitudes. National Transportation Safety Board (NTSB) data provided a measure of the comparative risks posed by control and performance inadequacies. Pilot training literature, as well as both pilot and instructor levels of awareness, indicated considerable misunderstanding of relevant aerodynamic principles. Virtually total emphasis has been devoted to directional control, which represents but one-third of the hazard. Regardless of circumstances, five degrees of bank is commonly believed to be the best available procedure for engine out flight. Mathematical analysis has been used to show that the optimum performance bank angle depends on several factors. In marginal rate of climb scenarios, the optimum bank is much smaller than five degrees. Wind tunnel experiments validated the analytical work and suggested substantially improved climb performance was achievable, with adequate control, by flying at zero sideslip. Flight tests in three light twin airplane models verified that angle of bank strongly influences rate of climb. Best climb resulted at the small angles of bank corresponding to zero sideslip. Increasing bank to five degrees degraded climb performance approximately 75-90 feet per minute from optimum. This penalty was equivalent to a weight addition of up to nine percent or a density altitude increase of as much as 1900 feet.

Term twins with discordant birth weights: observations at birth and one year.

Sixteen pairs of term discordant twins (weight discrepancy of more than 20% when the lighter twin was compared to the heavier) were evaluated at birth. Weight, length, head circumference, anterior fontanel area, and combined ossification of the knee epiphyses were measured, and ponderal index (weight/length ratio) calculated. The most severely growth retarded infants had markedly decreased ossification and larger anterior fontanels. Eleven pairs had physical measurements at one year of age. With individual exceptions, the lighter twins at birth remained smaller in all dimensions. Despite these persistent differences between twin pairs, the values for length at one year of age were within normal limits for both the heavier and lighter twins. Infants without ossification at birth had a greater incremental linear growth by one year than those infants with ossification.

Engine Failure in Light Twin‐Engine Aircraft

A study of accidents following engine failure in light twin engine aircraft showed that the most common factor in the accidents over a five‐year period was the apparent lack of crew proficiency in response to the emergencies, the National Transportation Safety Board said today.

Field Observations of the Persistence of AgI-NH4I-Acetone Ice Nuclei in Daylight

Abstract A field method of estimating the persistence of a commonly used silver iodide seeding agent is described. The method involved measurement of the AgI plume structure at two downwind distances from the ground generator(s). Distances between the nine available pairs of downwind measurement planes ranged from approximately 10 to 100 km. An NCAR acoustical ice nucleus counter in a light twin aircraft was used to sample the AgI plumes. A series of passes was made through the entire vertical and horizontal extent of the plume at each downwind distance. These measurements, together with pilot balloon observations, permitted calculation of the flux of AgI through each vertical cross-sectional plane. The difference in flux measurements yielded an estimate of the persistence of the seeding agent over the period of transport between the two vertical planes. This method was applied at three separate locations, during different seasons, and with various degrees of cloudiness. Resulting estimates of deactivatio...

Fontanel size and epiphyseal ossification in neonatal twins discordant by weight.

Size of the anterior fontanel and ossification of the epiphyseal centers at the knee were measured in 13 "discordant" twin pairs. There was a highly significant (p smaller than 0.01) negative correlation between fontanel size and epiphyseal ossification. Severe intrauterine growth retardation (demonstrated by the lighter twin) may result in retardation of membranous as well as enchondral ossification.

Instrumenting Light Aircraft for Air Pollution Research

Light aircraft and helicopters have been occasionally used to conduct aerial traverses for a single pollutant or atmospheric tracer. The continuous analyzer or sample collector is temporarily tied down with a seat belt or hand held. Flight variables are visually observed and written on the recorder chart, a notebook or possibly voice-recorded on a portable tape recorder. The versatile airborne instrumentation package described can measure and record up to 27 pollutant and flight variables from a Cessna Skymaster center-line thrust, light twin. Real-time analysis instrumentation include non-dispersive infrared analyzers for CO2, CO, and hydrocarbons, conductivity and coulometric analyzers for sulfur dioxide and sulfur-containing gases, and Charlson-Ahlquist visual range nephelometer. A Battelle “bulk sampler” is used to collect particulates for weighing and microscopic examination. Indicated air speed, altitude, rate of climb, magnetic heading, temperature, and relative humidity are continuously measured. ...

Apron Design for Light Airplanes

Design of parking aprons for single engine and light twin engine aircraft; standard dimensions are suggested for laying out tie-downs, and various geometric configurations are analyzed; tables give number and dimensions of single engine and twin engine aircraft; requirements for based aircraft and fixed base operator’s aprons, and for transient, fueling, and unloading aprons.