Evidence for the presence of turbulent attenuation on low-elevationangle Earth-space paths. 2. Frequency scaling of scintillation intensityon a 10° path

For pt.1 see ibid., vol.45, no.1, p.73-84 (1997). This paper presents the results of and conclusions drawn from two experimental studies of low-elevation, slant-path scintillation. Part I related to 11.2-GHz measurements at an elevation angle of 3.3°. Part II describes 14- and 11-GHz observations made on a (nominal) 10° path over a four year period. The resulting time-series data have enabled frequency scaling to be investigated in some depth. Scintillation occurring during periods unassociated with fading is found to be well modeled in its frequency scaling behavior by classical theories of clear air turbulence (CAT). This is not the case, however, for scintillation that occurs during, just before, or just after rain-induced fading. A rapidly fluctuating attenuation mechanism, not separable from CAT-induced scintillation on the basis of its spectrum alone, is thought to be responsible for this anomalous frequency-scaling result     

Comparison between thallium-201 and technetium-99m-tetrofosmin uptake with sustained low flow and profound systolic dysfunction

Technetium-99m-tetrofosmin uptake was compared to that of 201Tl in the setting of low flow and systolic dysfunction. METHODS: In nine open-chested dogs, a severe left anterior descending (LAD) coronary artery stenosis resulted in a 54.3% mean flow reduction and decreased left ventricular thickening from 21% +/- 1% to -3 +/- 2%. After 30 min, 37 MBq (1 mCi) of 201Tl and microspheres were injected and initial and 2-hr redistribution images acquired. Two hours later, 370 MBq (10 mCi) of 99mTc-tetrofosmin and microspheres were injected and an image was obtained. LAD: left circumflex (LCX) count ratios for both tracers and flows were calculated by well counting postmortem, and 201Tl and 99mTc-tetrofosmin defect magnitudes were determined by quantitative image analysis. RESULTS: LAD:LCx flow ratios were similar during 201Tl and 99mTc-tetrofosmin injections (0.48 +/- 0.04 versus 0.49 +/- 0.05, p = n.s.). Final 201Tl activity (0.66 +/- 0.04) was significantly higher than 99mTc-tetrofosmin (0.55 +/- 0.05; p < 0.05). LAD/LCx 99mTc-tetrofosmin image defect count ratio was similar to 201Tl defect count ratio on the initial rest 201Tl scan (0.57 +/- 0.03 versus 0.56 +/- 0.02, p = ns), but significantly less than 201Tl defect count ratio at 2 hr (0.57 +/- 0.03 versus 0.65 +/- 0.02, p < 0.05). CONCLUSION: In a low-flow model with profound systolic dysfunction, myocardial 99mTc-tetrofosmin uptake ( > 50%) reflective of viability was observed in the asynergic zone perfused by the stenotic LAD.     

Adult-only exposure of male rats to a diet of high phytoestrogen content increases apoptosis of meiotic and post-meiotic germ cells

Apoptosis plays a critical role in regulating sperm production. Removal of androgens and gonadotropins, or estrogen administration induces germ cell apoptosis. It is hypothesized that dietary phytoestrogens increase apoptosis of developing germ cells, decreasing sperm production. This study aimed to test this in rats fed a high phytoestrogen diet only during adulthood. Male Wistar rats used in this study were offspring of females maintained on a low phytoestrogen diet prior to conception through to weaning. After weaning, juveniles were fed the same low phytoestrogen diet into adulthood. A cohort of males were transferred to a high phytoestrogen diet for 24 days and subsequently testes were collected from all animals. In the high phytoestrogen fed group, homogenization-resistant sperm counts were significantly decreased, as were epididymal sperm counts. Morphometric analysis determined round and elongated spermatid volumes to be significantly decreased, but seminiferous tubule lumen diameters to be significantly increased. TUNEL analysis determined that apoptosis of spermatocytes and round spermatids was significantly greater in the high phytoestrogen fed rats. Neither plasma gonadotropin concentrations nor testicular testosterone were altered. In conclusion, exposure of the adult male rat to a high phytoestrogen diet disrupts spermatogenesis, increasing germ cell apoptosis. This effect is independent of the hypothalamo-pituitary-testicular axis and is likely due to disruption of estrogen's actions in the testis.     

Ultra-high-precision alignment of the elastomerically mounted elements of the science camera lenses for the Mars Science Laboratory (MSL) rover

Cameras built for space exploration are required to meet stringent environmental conditions, such as thermal and dynamic loads for both the optics (camera lens) and imaging electronics. On a multitude of spaceborne imaging instruments, optical elements are supported in their mounts via an elastomeric bonding approach using a room temperature vulcanizing silicone as the bonding agent. Employing this integration method, we achieved element-to-element alignment, measured as the total indicated runout, using a high-precision contact probe to be on the order of half a wavelength of He-Ne laser light, or 0.3?μm, on the Malin Space Science Systems lenses for the Mars Science Laboratory (MSL) cameras. This is a higher precision than the current industry state-of-the-art, and it was achieved for the very challenging small diameter lens elements. This paper describes the design philosophy, implementation, and integration method that resulted in achieving this level of precision for interelement alignment. The results are based on actual measurements that were made during the process of building the MSL rover's science camera lenses, namely Mastcams, the Mars Hand Lens Imager, and the Mars Descent Imager. The optical designs of these cameras lenses are described in detail in [Opt. Eng.48, 103002 (2009)], while further information on the four science cameras can be found at http://www.msss.com.     

Microwave dielectric properties of alkaline earth orthosilicates M2SiO4 (M=Ba, Sr, Ca)

Alkaline earth orthosilicates M₂SiO₄ (M=Ba, Sr, Ca) ceramics were prepared by solid state ceramic route and their microwave dielectric properties were investigated. M₂SiO₄ ceramics have ε_r in the range 8.5-13. At microwave frequencies, the Q_u × f obtained were 17,900 GHz, 19,100 GHz and 26,100 GHz for Ba₂SiO₄, Sr₂SiO₄ and Ca₂SiO₄ respectively. The τ_f of Ba₂SiO₄ was − 17 ppm/°C, whereas Sr₂SiO₄ and Ca₂SiO₄ exhibited high values of τ_f, − 205 ppm/°C and − 89 ppm/°C respectively. The coefficient of thermal expansion (α_l) of the orthosilicates was also studied.     

Nutrient and trace-metal removal by Bauxsol pellets in wastewater treatment

In this study, Bauxsol pellets packed in PVC columns were used to remove nutrients and trace-metals from municipal wastewater during a 6 months field trial. Bauxsol pellet columns showed a high phosphate removal rate via precipitation of PO(4)(3-) with Ca(2+) and Mg(2+) ions: at 90% in the 1st month; at 80% from the second to fifth months; and at 60% in the sixth month. Pellet bound total phosphorus and Colwell phosphorus were 7.3 g/kg and 2 g/kg and are about 20 times the concentrations found in most fertile soils. Trace-metals in effluents were bound, probably irreversibly under the columns' environmental conditions, to the Bauxsol minerals that have high surface area to volume ratios and high charge to mass ratios. Experimental results showed a complex nitrogen cycle operating within the Bauxsol pellet columns including anoxic nitrification, denitrification, and anammox processes. Although a transient pH spike, associated with the release of unreacted CaO from the cement binder used in the pellets, was observed, this may be readily corrected through post-treatment pH adjustment. Hence, the geochemistry of Bauxsol pellets can effectively remove and bind nutrients and trace-metals during wastewater treatment, and further research may show that saturated spent pellets can be used as fertilizer.     

Nanotribology Application in the Coining Industry (I)—Turn off Stamping Oil Sprayer during Coining

The most common tribological cases involve two solid surfaces repeatedly contacting each other. During coining, however, a pair of dies strikes each blank that has been stamped only once. The requirements of the surface physical and chemical properties for coining are different compared to the common tribological conditions. For example, a low-viscosity stamping oil is used during coining in the United States Mint, as well as other industries. Under coining tonnage this small amount of liquid on die surfaces may promote microcrack propagation. In this case, lubrication does not prolong die life but shortens it.

In this work, the lubrication mechanism during coining was studied. A lubricant layer was applied on blank surfaces before coining. Based on the special stamping condition, blank surfaces must meet several tribological requirements. According to these requirements, a new technology was employed and the use of a new lubricant was implemented. As a result, fatigue die life was increased almost three times on high-volume production lines and coin surface quality was improved.     

Detection and diagnosis of bearing and cutting tool faults using hidden Markov models

Over the last few decades, the research for new fault detection and diagnosis techniques in machining processes and rotating machinery has attracted increasing interest worldwide. This development was mainly stimulated by the rapid advance in industrial technologies and the increase in complexity of machining and machinery systems. In this study, the discrete hidden Markov model (HMM) is applied to detect and diagnose mechanical faults. The technique is tested and validated successfully using two scenarios: tool wear/fracture and bearing faults. In the first case the model correctly detected the state of the tool (i.e., sharp, worn, or broken) whereas in the second application, the model classified the severity of the fault seeded in two different engine bearings. The success rate obtained in our tests for fault severity classification was above 95%. In addition to the fault severity, a location index was developed to determine the fault location. This index has been applied to determine the location (inner race, ball, or outer race) of a bearing fault with an average success rate of 96%. The training time required to develop the HMMs was less than 5 s in both the monitoring cases.     

Influence of Proportion of Skin Present During Malaxing on Pigment Composition of Cold Pressed Avocado Oil

The effect of the proportion of ‘Hass’ avocado skin tissue present during aqueous cold pressed avocado oil extraction on the pigment concentration and oil quality was determined. Increasing amounts of skin (i.e., from 0 to 100% of available skin) were included with the flesh before grinding and malaxing in a laboratory-scale cold pressed extraction process. The recovered oils were analyzed for oil quality and color. The pigment concentrations in the oil were determined by high performance liquid chromatography (HPLC). With increasing amounts of skin addition, there was an increase in the green color, as indicated by hue angle, of the avocado oils. There were also increased concentrations of carotenoids and chlorophylls in the oil as the proportion of skin during malaxing was increased. The lutein concentration in the oils increased from 1.13 to 3.21 μg g⁻¹ as the amount of skin added to the malaxer increased from 0 to 100% skin, and the total chlorophyll concentration in the same oils increased from 7.3 to 27.5 μg g⁻¹. The green color of cold pressed avocado oil and the pigment concentrations can be increased by adding more skin to the malaxer during oil extraction.