X-ray properties of UV-selected star forming galaxies at z~1 in the Hubble Deep Field North

We present an analysis of the X-ray emission from a large sample of ultraviolet (UV) selected, star forming galaxies with 0.74<z<1.32 in the Hubble Deep Field North (HDF-N) region. By excluding all sources with significant detected X-ray emission in the 2 Ms Chandra observation we are able to examine the properties of galaxies for which the emission in both UV and X-ray is expected to be predominantly due to star formation. Stacking the X-ray flux from 216 galaxies in the soft and hard bands produces significant detections. The derived mean 2-10 keV rest-frame luminosity is 2.97+/-0.26x10^(40) erg/s, corresponding to an X-ray derived star formation rate (SFR) of 6.0+/-0.6 Msolar/yr. Comparing the X-ray value with the mean UV derived SFR, uncorrected for attenuation, we find that the average UV attenuation correction factor is \~3. By binning the galaxy sample according to UV magnitude and colour, correlations between UV and X-ray emission are also examined. We find a strong positive correlation between X-ray emission and rest-frame UV emission. A correlation between the ratio of X-ray-to-UV emission and UV colour is also seen, such that L(X)/L(UV) increases for redder galaxies. Given that X-ray emission offers a view of star formation regions that is relatively unaffected by extinction, results such as these can be used to evaluate the effects of dust on the UV emission from high-z galaxies. For instance we derive a relationship for estimating UV attenuation corrections as a function of colour excess. The observed relation is inconsistent with the Calzetti et al. (2000) reddening law which over predicts the range in UV attenuation corrections by a factor of ~100 for the UV selected z~1 galaxies in this sample (abridged).Comment: 10 pages, 7 figures, accepted for publication in MNRA

Studies on mechanical behavior of glass epoxy composites with induced defects and correlations with NDT characterization parameters

Degradation in mechanical properties (compression, flexural and ILS) of glass epoxy composite laminates with induced defects (simulating delaminations) was studied. The defects were characterized by using the A-scan ultrasonic pulse-echo technique. The two A-scan parameters, viz. the back wall echo amplitude and time of flight, were followed respectively, as functions of the defect size (diameter) and its location in the laminate thickness. The mechanical properties of laminates were evaluated destructively for different defect sizes and locations. An attempt has been made to express the mechanical properties in terms of the two NDT scan parameters characterizing the defects and empirical equations presente

Dynamic analysis of a pre-and-post ice impacted blade

The dynamic characteristics of an engine blade are evaluated under pre-and-post ice impact conditions using the NASA in-house computer code BLASIM. The ice impacts the leading edge of the blade causing severe local damage. The local structural response of the blade due to the ice impact is predicted via a transient response analysis by modeling only a local patch around the impact region. After ice impact, the global geometry of the blade is updated using deformations of the local patch and a free vibration analysis is performed. The effects of ice impact location, size and ice velocity on the blade mode shapes and natural frequencies are investigated. The results indicate that basic nature of the mode shapes remains unchanged after impact and that the maximum variation in natural frequencies occurs for the twisting mode of the blade

Structural tailoring of aircraft engine blade subject to ice impact constraints

Results are presented for the minimum weight design of SR2 unswept blade made of (titanium/graphite-epoxy/titanium) sub s fiber composite. The blade which is rotating at high RPM is subject to ice impact. The root chord length, blade thicknesses at five stations, and graphite-epoxy ply orientation are chosen as design variables. Design constraints are placed on the behavior variables: local leading edge strain and root damage parameter (combined stress failure criteria) as a function due to ice impact, maximum spanwise centrifugal stress at the root of the deformed blade due to local damage, first three natural frequencies, and resonance margin after impact. The method of feasible directions is employed to solve the inequality constrained minimization problem. The effect of ice speed and the ice impact location on the final design are discussed

Root damage analysis of aircraft engine blade subject to ice impact

The blade root response due to ice impact on an engine blade is simulated using the NASA in-house code BLASIM. The ice piece is modeled as an equivalent spherical object impacting on the leading edge of the blade and has the velocity opposite to that of the aircraft with direction parallel to the engine axis. The effect of ice impact is considered to be an impulse load on the blade with its amplitude computed based on the momentum transfer principle. The blade response due to the impact is carried out by modal superposition using the first three modes. The maximum dynamic stresses at the blade root are computed at the quarter cycle of the first natural frequency. A combined stress failure function based on modified distortion energy is used to study the spanwise bending damage response at the blade root. That damage function reaches maximum value for very low ice speeds and increases steeply with increases in engine speed

Farming With Flax

As Iowa\u27s praire sod was broken, sometimes the first crop on the land was flax. Since those early days Iowa has grown some flax every year. Through the war years, oil was needed and the flax average increased. We still need more flax in order to get its products-linseed oil and linseed meal

Think Piece. Learning of Environment(s) and Environment(s) of Learning

As we reflect on the 30 years that have passed since the first intergovernmental conference on environmental education that was held in Tbilisi, Georgia, it might be useful to review how learning of environment(s) has changed over time and also how environment(s) of learning have changed. And also, what challenges these changes present for contemporary societies. The Tbilisi conference took place at a crucial time in human history, following sharpened awareness in the 1960s of human activity impacting negatively on natural systems. But, also a time when humans were still optimistic that environmental destruction could be reversed and that education might play a role in achieving it. What transpired at the conference might therefore be understood as a meeting where representatives of governments proactively defined objectives, goals and principles for guiding environmental education activities, in view of an impending socio-ecological crisis (at the time) (UNESCO-UNEP, 1978). The focus of this short essay is on learning, therefore we first draw attention to some of the Tbilisi Principles pertinent to learning of environments and environments of learning. The first Tbilisi Principle suggests that environmental education should consider the environment in its totality, implying that learning about/in/for environments should involve all dimensions of environments and how these&nbsp; dimensions interact with one another. This Principle is linked to Principle 4 which states that the approach to learning should be interdisciplinary. Furthermore, Principle 2 states that learning should be a continuous lifelong process and Principle 8 states that learners should be active participants in planning their own learning experiences, and that they should make their own decisions as well as take responsibility for their decisions

Barley in Iowa

Barley yields in Iowa are higher than those for oats, but in spite of this 15 times more acres are sown to oats than to barley. During the 10 year period, 1925-34, the farms of Iowa produced average acre yields of 1,007 pounds of oats on 6,000,000 acres and 1,238 pounds of barley on 460,000 acres. Figure 1, presenting data from the Iowa Year Book of Agriculture, shows the relative acreage and acre yields of the two crops from 1900 to 1934. In order that a direct comparison may readily be made, the yields of barley have been converted into units of 32 pounds, corresponding to a standard bushel of oats. These data indicate that while the spread between the yields of the two crops was somewhat greater during the 10 year period, 1920-29, than during the preceding decade, the same general relation, in both yield and acreage, has existed for more than 30 years