•Lunar impact monitoring has been used to determine the flux of meteoroids in the 30g to a few kilograms size range.•A catalog of 126 photometrically calibrated impact flashes is presented.•A ...rigorous approach for photometric calibration of impact flash observations and calculation of flash energy is described.•Rates of observed flashes are correlated with meteor showers.•A large impact flash in March 2013 gave crater size estimates consistent with the crater measured by LRO.
The flashes from meteoroid impacts on the Moon are useful in determining the flux of impactors with masses as low as a few tens of grams. A routine monitoring program at NASA’s Marshall Space Flight Center has recorded over 300 impacts since 2006. A selection of 126 flashes recorded during periods of photometric skies was analyzed, creating the largest and most homogeneous dataset of lunar impact flashes to date. Standard CCD photometric techniques were applied to the video and the luminous energy, kinetic energy, and mass are estimated for each impactor. Shower associations were determined for most of the impactors and a range of luminous efficiencies was considered. The flux to a limiting energy of 2.5×10−6kT TNT or 1.05×107J is 1.03×10−7km−2h−1 and the flux to a limiting mass of 30g is 6.14×10−10m−2yr−1 at the Moon. Comparisons made with measurements and models of the meteoroid population indicate that the flux of objects in this size range is slightly lower (but within the error bars) than flux at this size from the power law distribution determined for the near Earth object and fireball population by Brown et al. (Brown, P.G., Spalding, R., ReVelle, D., Tagliaferri, E., Worden, S. 2002. Nature 420, 294–296). Size estimates for the crater detected by Lunar Reconnaissance Orbiter from a large impact observed on March 17, 2013 are also briefly discussed.
Video observations of lunar impact flashes have been made by a number of researchers since the late 1990's and the problem of determination of the impact energies has been approached in different ...ways Bellot Rubio et al. (2000a, b), Yanagisawa et al. (2008), Bouley et al. (2012), Suggs et al. (2014), Rembold and Ryan (2015), Ortiz et al. (2015), Madiedo et al. (2015). The wide spectral response of the unfiltered video cameras in use for all published measurements necessitates color correction for the standard filter magnitudes available for the comparison stars but this is not typically considered. In our approach, the published color of the comparison star and an estimate of the color of the impact flash is used to correct it to the chosen filter bandpass. Magnitudes corrected to standard filters are then used to determine the luminous energy in the filter bandpass according to the stellar atmosphere calibrations of Bessell et al. (1998). In this paper we compare the various photometric calibration techniques and calculation of luminous energy (radiometry) of impact flashes. This issue has significant implications for determination of luminous efficiency, predictions of impact crater sizes for observed flashes, and the determination of the flux of meteoroids in the 10s of grams to kilograms mass range.
•Radiometric calibration of video recordings of lunar impact flashes has been accomplished by a variety of techniques.•The use of unfiltered video cameras adds complexity to calibration and determination of luminous energy.•Color corrections for the comparison stars and the impact flashes are necessary.•Comparison of luminous energies from various researchers demonstrates differences due to calibration techniques.
We observed the Lunar Crater Observation and Sensing Satellite (LCROSS) lunar impact on 9 October 2009 using three telescope and instrument combinations in southern New Mexico: the Agile camera with ...a V filter on the Astrophysical Research Consortium 3.5 m telescope at Apache Point Observatory (APO), a StellaCam video camera with an R filter on the New Mexico State University (NMSU) 1 m telescope at APO, and a Goodrich near‐IR (J and H band) video camera on the NMSU 0.6 m telescope at Tortugas Mountain Observatory. The three data sets were analyzed to search for evidence of the debris plume that rose above the Cabeus crater shortly after the LCROSS impact. Although we saw no evidence of the plume in any of our data sets, we constrained its surface brightness through analysis of our photometrically calibrated data. The minimum surface brightness that we could have detected in our Agile data was 9.69 magnitudes arc sec−2, which is 177 times fainter than the brightest part of the foreground ridge of Cabeus. In our near‐IR data, our minimum detectable surface brightness was 8.58 magnitudes arc sec−2, which is 370 times fainter than the brightest part of the foreground ridge in the J and H bands. The debris plume was detected by the LCROSS shepherding spacecraft and the Diviner radiometer on the Lunar Reconnaissance Orbiter. Given the plume radiance observed by LCROSS, we cannot distinguish between a conical or cylindrical plume geometry because when seen from Earth, both are below our detection thresholds.
Key Points
We did not detect the debris plume caused by the LCROSS impact
We placed limits on the surface brightness of the plume as seen from Earth
We cannot distinguish between conical and cylindrical plume geometries
Purpose: There are excellent arguments in favor of the preferential use of prosthetic grafts above the knee for the treatment of infrainguinal occlusive disease. This approach has been popularized on ...the basis of the seemingly acceptable results when using polytetrafluoroethylene (PTFE). However, in many centers, knitted Dacron polyester has been used in these patients, and there are several studies that show equivalent and, in some, superior results with Dacron when compared with PTFE. The purpose of this study was to examine these results in a definitive way.
Methods: A randomized prospective trial in eight clinical academic centers in the United States and Canada was initiated in 1991. Two hundred forty-four patients eligible for such a study, by virtue of criteria extant in each institution at the time, were centrally randomized. They underwent placement of either a knitted Dacron polyester graft impregnated with collagen or a thin-wall expanded reenforced PTFE graft to the above-knee popliteal artery, usually from the common femoral artery. They were frequently observed by protocol for as long as 5 years by a physical examination noninvasive hemodynamic study, including duplex scanning in many instances. Continuing patency was noted, as were other potential adverse outcome events. The data were analyzed by the log-rank test for cumulative patency and expressed as Kaplan-Meier curves. Data were further analyzed with a Cox proportional hazards model.
Results: There were no differences in graft groups in demographic or comorbid factors. The procedural mortality rate was zero, and the morbidity rate was low (6.5%). The long-term patient survival rate was excellent (77% at 3 years). At the end of these years, no statistical significance in primary or secondary patency rates was observed between the two grafts (primary patency rate, 62% ± 14.4% for Dacron; 57% ± 15.5% for PTFE). No unexpected adverse outcomes on limb status were noted. Patency rates in both graft groups were inferior in patients who received small grafts (5 to 6 mm vs 7 to 8 mm; hazards ratio, 4.15) and younger (<65 years) smoking patients.
Conclusions: The fact that these two prosthetic grafts performed in equivalent fashion in a controlled, well-conducted prospective study is not surprising in spite of the previous work that suggested differences. If the preferential use of synthetic bypass grafts above the knee is to be used, it should be restricted to older nonsmokers with favorable anatomy. In that instance, the choice of graft material will depend on handling characteristics and cost. Above-knee prostheses should be only selectively used in younger, smoking patients, and graft size should be carefully considered in patients who undergo this operation. (J Vasc Surg 1997;25:19-28.)
We investigated the importance of the myosin head in thick filament formation and myofibrillogenesis by generating transgenic Drosophila lines expressing either an embryonic or an adult isoform of ...the myosin rod in their indirect flight muscles. The headless myosin molecules retain the regulatory light‐chain binding site, the α‐helical rod and the C‐terminal tailpiece. Both isoforms of headless myosin co‐assemble with endogenous full‐length myosin in wild‐type muscle cells. However, rod polypeptides interfere with muscle function and cause a flightless phenotype. Electron microscopy demonstrates that this results from an antimorphic effect upon myofibril assembly. Thick filaments assemble when the myosin rod is expressed in mutant indirect flight muscles where no full‐length myosin heavy chain is produced. These filaments show the characteristic hollow cross‐section observed in wild type. The headless thick filaments can assemble with thin filaments into hexagonally packed arrays resembling normal myofibrils. However, thick filament length as well as sarcomere length and myofibril shape are abnormal. Therefore, thick filament assembly and many aspects of myofibrillogenesis are independent of the myosin head and these processes are regulated by the myosin rod and tailpiece. However, interaction of the myosin head with other myofibrillar components is necessary for defining filament length and myofibril dimensions.
The persistence of drug resistant cell populations following chemotherapeutic treatment is a significant challenge in the clinical management of cancer. Resistant subpopulations arise via both cell ...intrinsic and extrinsic mechanisms. Extrinsic factors in the microenvironment, including neighboring cells, glycosaminoglycans, and fibrous proteins impact therapy response. Elevated levels of extracellular fibrous proteins are associated with tumor progression and cause the surrounding tissue to stiffen through changes in structure and composition of the extracellular matrix (ECM). We sought to determine how this progressively stiffening microenvironment affects the sensitivity of breast cancer cells to chemotherapeutic treatment. MDA-MB-231 triple negative breast carcinoma cells cultured in a 3D alginate-based hydrogel system displayed a stiffness-dependent response to the chemotherapeutic doxorubicin. MCF7 breast carcinoma cells cultured in the same conditions did not exhibit this stiffness-dependent resistance to the drug. This differential therapeutic response was coordinated with nuclear translocation of YAP, a marker of mesenchymal differentiation. The stiffness-dependent response was lost when cells were transferred from 3D to monolayer cultures, suggesting that endpoint ECM conditions largely govern the response to doxorubicin. To further examine this response, we utilized a platform capable of dynamic ECM stiffness modulation to allow for a change in matrix stiffness over time. We found that MDA-MB-231 cells have a stiffness-dependent resistance to doxorubicin and that duration of exposure to ECM stiffness is sufficient to modulate this response. These results indicate the need for additional tools to integrate mechanical stiffness with therapeutic response and inform decisions for more effective use of chemotherapeutics in the clinic.
Purpose: Arteriography is the diagnostic test of choice before lower extremity revascularization, because it is a means of pinpointing stenotic or occluded arteries and defining optimal sites for the ...origin and termination of bypass grafts. We evaluated whether a duplex ultrasound scan, used as an alternative to arteriography, could be used as a means of accurately predicting the proximal and distal anastomotic sites in patients requiring peripheral bypass grafts and, therefore, replace standard preoperative arteriography.
Methods: Forty-one patients who required infrainguinal bypass grafts underwent preoperative duplex arterial mapping (DAM). Based on these studies, an observer blinded to the operation performed predicted what operation the patient required and the best site for the proximal and distal anastomoses. These predictions were compared with the actual anastomotic sites chosen by the surgeon.
Results: Whether a femoropopliteal or an infrapopliteal bypass graft was required was predicted correctly by means of DAM in 37 patients (90%). In addition, both anastomotic sites in 18 of 20 patients (90%) who had femoropopliteal bypass grafts and 5 of 21 patients (24%) who had infrapopliteal procedures were correctly predicted by means of DAM.
Conclusion: DAM is a reliable means of predicting whether patients will require femoropopliteal or infrapopliteal bypass grafts, and, when a patient requires a femoropopliteal bypass graft, the actual location of both anastomoses can also be accurately predicted. Therefore, DAM appears able to replace conventional preoperative arteriography in most patients found to require femoropopliteal reconstruction. Patients who are predicted by means of DAM to require crural or pedal bypass grafts should still undergo preoperative contrast studies to confirm these results and to more precisely locate the anastomotic sites. (J Vasc Surg 1999;29:100-9.)
A partially saturated linear polyester based on poly(propylene fumarate) (PPF) was synthesized for potential application in filling skeletal defects. The synthesis was carried out according to a ...two-step reaction scheme. Propylene glycol and fumaryl chloride were first combined to form
an intermediate fumaric diester. The intermediate was then subjected to a transesterification to form the PPF-based polymer. This method allowed for production of a polymer with a number average molecular weight up to 1500 and a polydispersity index of 2.8 and below. The polymeric backbone
structure was investigated through the use of FTIR and NMR. Kinetic studies of the transesterification allowed mapping of the molecular weight increase with reaction time. The final product was also characterized by thermal and solubility analysis.
Skeletal muscle injury resulting in tissue loss poses unique challenges for surgical repair. Despite the regenerative potential of skeletal muscle, if a significant amount of tissue is lost, skeletal ...myofibers will not grow to fill the injured area completely. Prior work in our lab has shown the potential to fill the void with an extracellular matrix (ECM) scaffold, resulting in restoration of morphology, but not functional recovery. To improve the functional outcome of the injured muscle, a muscle-derived ECM was implanted into a 1 x 1 cm(2), full-thickness defect in the lateral gastrocnemius (LGAS) of Lewis rats. Seven days later, bone-marrow-derived mesenchymal stem cells (MSCs) were injected directly into the implanted ECM. Partial functional recovery occurred over the course of 42 days when the LGAS was repaired with an MSC-seeded ECM producing 85.4 +/- 3.6% of the contralateral LGAS. This was significantly higher than earlier recovery time points (p < 0.05). The specific tension returned to 94 +/- 9% of the contralateral limb. The implanted MSC-seeded ECM had more blood vessels and regenerating skeletal myofibers than the ECM without cells (p < 0.05). The data suggest that the repair of a skeletal muscle defect injury by the implantation of a muscle-derived ECM seeded with MSCs can improve functional recovery after 42 days.
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