Improving high-altitude UV–Vis resistance of PBO braided tendons of NASA’s super pressure balloons

Super pressure balloons (SPBs) are used by the National Aeronautics and Space Administration (NASA) for ultra-long duration ballooning (ULDB) missions which carry various scientific explorations to support space and earth sciences research activities. The resistance to photo-degradation of load-bearing braided tendons of SPBs is critical to the success of ULDB missions. Recognizing the critical need to improve UV and visible light (UV–Vis) protective performance of p-phenylene-2, 6-benzobisoxazole (PBO) braids, North Carolina State University and NASA’s Balloon Program collaborated to investigate the effectiveness of sheath extrusion method in improving the UV–Vis resistance of tendons. This study included two PBO tendon types – 48,000 (48k) denier tendons and 72,000 (72k) denier tendons. Using a sheath extrusion method, the tendons were covered with UV protective sheath of low-density polyethylene containing two types of UV inhibitors – TiO2 rutile nanoparticles and PolyOne PE White CC®. Bare and sheathed tendons were subjected to artificial UVB exposure in the lab as well as to both high altitude and ground exposure during flight missions conducted by NASA. Protection against radiation exposure was evaluated by determining the loss of tensile strength after exposure. UV–Vis protection of tendons improved with an increase in sheath thickness as well as UV inhibitor content in the sheath. The results also showed that 72k denier braids had higher resistance against UV degradation compared to 48k denier braids. In-flight exposure results confirmed the comparative UV protective performance of tendons exposed to accelerated artificial UVB exposure in lab. 72k denier tendon covered with sheath containing 10% PE White CC® (sheath thickness of 0.37 mm) experienced the lowest strength loss among all tendon samples to high-altitude exposure during flight missions. The study has also utilized UV–Vis transmittance of the sheath covering the braids as a method of evaluating the performance of the protective sheaths

The Risks of Renal Angiomyolipoma: Reviewing the Evidence

Renal angiomyolipoma (RAML), though a rare benign tumor, may impose a significant morbidity or even mortality due to its unique characteristics and the complications subsequent to its treatment. The classic tumor variant is composed of smooth muscular, vascular, and fatty components. The most straightforward diagnosis is when the fat component is abundant and gives a characteristic appearance on different imaging studies. In fat-poor lesions, however, the diagnosis is difficult and presumed a renal cell carcinoma. Yet, some variants of RAML, though rare, express an aggressive behavior leading to metastasis and mortality. The challenge lies in the early detection of benign variants and identifying aggressive lesions for proper management. Another challenge is when the vascular tissue component predominates and poses a risk of hemorrhage that may extend to the retroperitoneum in a massive life-threatening condition. The predicament here is to identify the characteristics of tumors at risk of bleeding and provide a prophylactic treatment. According to the clinical presentation, different treatment modalities, prophylactic or therapeutic, are available that span the spectrum of observation, embolization, or surgery. Renal impairment may result from extensive tumor burden or as a complication of the management itself. Improvement of diagnostic techniques, super-selective embolization, nephron-sparing surgery, and late treatment with the mammalian target of rapamycin inhibitors have provided more effective and safe management strategies. In this review, we examine the evidence pertaining to the risks imposed by RAML to the patients and identify merits and hazards associated with different treatment modalities

AC conductivity and dielectric properties of In

Stoichiometric In2S3 films were prepared by thermal evaporation technique onto clean glass substrates. According to X-ray investigations, the as-deposited films were in amorphous state. Both the ac conductivity and dielectric constants were measured in the frequency range 100 Hz−100 kHz at different temperatures. Different parameters such as the frequency exponent parameter s, the density of states near the Fermi level $N(E_{\rm F})$, the activation energy $(\Delta E)$ and the optical band gap Eg of In2S3 amorphous thin films were estimated. The hopping conduction was recognized as the conduction mechanism for the investigated films

Effect of structural parameters on the impact properties of multilayer composites from Tururi palm ( Manicaria saccifera

Tururi (Manicaria saccifera Gaertn.) is a natural fibrous mesh which protects the fruits of the Amazon Ubuçu palm tree. This research targets developing natural fiber composites from Tururi fibers and characterizing their impact properties. A set of composites from Tururi fiber with different construction parameters (number of layers, fiber orientation, and fiber volume fraction) were manufactured. The results indicated that increasing the number of layers significantly increased the impact resistance up to a limit after which the resin penetration is impaired; moreover, stretching the preform significantly reduced the fiber volume fraction, and hence the impact properties. Finally, the fiber orientation had a negligible effect on the impact energy; yet, it had a significant effect on the failure mechanism

Optical properties of CdI

The transmittance (T) of thin films of CdI2, prepared by thermal evaporation technique on quartz substrates, have been measured over the wavelength range 200−900 nm. From analysis of the transmittance data, the optical constants, the refractive index (n) and the extinction coefficient (k), have been studied. Analysis of the refractive index (n) yields a low frequency dielectric constant, average oscillator strength and average oscillator energy. From analysis of the absorption coefficient (α), the fundamental absorption edge can be determined. Both allowed direct transitions and allowed indirect transitions are observed. The composition of films is checked using energy dispersive X-ray (EDX) spectroscopy technique. X-ray diffraction (XRD) measurements showed that the CdI2 films evaporated at room temperature substrates were characterized by a polycrystalline form. At large thicknesses the films indicated the inhomogeneity. The effect of annealing temperature (up to 523 K) on the film properties has been studied

Effect of film thickness and deposition rate on the AC electrical conductivity and dielectric properties of Sb

Measurements were carried out in the temperature range 293–453 K over the frequency range 100 Hz–100 kHz on the ac electrical properties of vacuum deposited SbxS1−x thin films of different thicknesses prepared with different deposition rates. The obtained experimental data have been analyzed with reference to various theoretical models. The ac conductivity increases with frequency according to the relation σac(ω) α ωs. The analysis shows that the correlated barrier-hopping (CBH) model is the most appropriate mechanism for the ac conduction in these films. The value of the dielectric constant slightly changed for higher frequencies irrespective of temperature change, whereas its value increases at higher temperature with the decrease in frequency. The dielectric loss has been found to increase with increase in temperature and decrease in frequency. The deposition rate and film thickness have a remarkable effect on ac conductivity and dielectric properties. The maximum barrier height wm is calculated from dielectric measurements according to Guintini et al. equation based on Elliott (CBH) model; which suggested the hopping of charge carriers over a potential barrier between charged defect states. The density of states was also calculated using Elliott model