Spacecraft launch depressurization loads

The pressure variation inside the launch vehicle fairing during climb through the atmosphere induces structural loads on the walls of closed-type spacecrafts or equipment boxes. If the evacuation of the air is not fast enough, excessive pressure loading can result in damage of elements exposed to the rising pressure jump, which depends mainly on the geometry of venting holes, the effective volume of air to be evacuated, and the characteristic time of pressure variation under the fairing. A theoretical study of the reservoir discharge forced by the fairing time-dependent pressure variation is presented. The basic mathematical model developed can yield both a numerical solution for the pressure jump and an asymptotic solution for the most relevant case, the small-prcssurc-jump limit, showing the dependence on a single nondimensional parameter: the ratio of the reservoir discharge to the fairing pressure profile characteristic times. The asymptotic solution validity range upper limit, obtained by comparison with the numerical solution, is determined by the starting of choked operation. Very high sensitivity of the maximum pressure jump to the ratio of characteristic times has been observed. Another relevant finding is that the pressure profiles for different launchers can be considered similar when rewritten in appropriate form and only their characteristic times are required for the analysis. The simple expressions of the asymptotic solution are a useful tool for preliminarily sizing the reservoir discharge geometry and estimating depressurization load

Vehicle induced loads on pedestrian barriers

This paper is a continuation of a previous one, Sanz-Andrés, Santiago-Prowald, Baker and Quinn (J. Wind Eng. Ind. Aerodyn. 91 (2003) 925) concerning the loads generated on a structural panel (traffic sign) by vehicle running along the road, although obviously, the results are also applicable to the effects of other moving vehicles such as trains. The structural panel was modelized as a large plate whose largest dimension is perpendicular to the vehicle motion direction. In this paper a similar approach is used to develop a mathematical model for the vehicle-induced load on pedestrian barriers, modelized as a large plate whose largest dimension is parallel to the vehicle motion direction. The purpose of the work is to develop a model simple enough to give analytical results, although with the physical phenomena correctly accounted for, such as to be able to explain, at least qualitatively, the main characteristics of the phenomenon, as observed in the experiments performed by Quinn et al. (J. Wind Eng. Ind. Aerodyn. 89 (2001) 831). Actually, in spite of the model simplicity, results of the theoretical model show a reasonable good quantitative agreement with the experimental results. The aim of this and previous publications is to provide to the transport infrastructure community with some simple tools that can help to explain, and in some cases also to compute, the unsteady loading produced by moving vehicles on persons and installations placed close to the roads or tracks

Vehicle-induced loads on traffic sign panels

The determination of the loads on traffic sign panels in the current standards does not, in general, take into account the vehicle-induced loads, as explained by Quinn, Baker and Wright (QBW in what follows) (J. Wind Eng. Ind. Aerodyn. 89 (2001) 831). On the other hand, a report from Cali and Covert (CC) (J. Wind Eng. Ind. Aerodyn. 84 (2000) 87) indicates that in highway sign support structures, vehicle-induced loads have led to premature failures in some cases. The aim of this paper is to present a mathematical model for the vehicle-induced load on a flat sign panel, simple enough to give analytical results, but able to explain the main characteristics of the phenomenon. The results of the theoretical model help to explain the behaviour observed in the experiments performed in previous studies

Energy harvesting from transverse galloping

Some elastic bluff bodies under the action of a fluid flow can experience transverse galloping and lose stability if the flow velocity exceeds a critical value. For flow velocities higher than this critical value, there is an energy transfer from the flow to the body and the body develops an oscillatory motion. Usually, it is considered as an undesirable effect for civil or marine structures but here we will show that if the vibration is substantial, it can be used to extract useful energy from the surrounding flow. This paper explores analytically the potential use of transverse galloping in order to obtain energy. To this end, transverse galloping is described by a one-degree-of-freedom model where fluid forces obey the quasi-steady hypothesis. The influence of cross-section geometry and mechanical properties in the energy conversion factor is investigated

Effect of Gadolinium Chloride on Liver Regeneration Following Thioacetamide-Induced Necrosis in Rats

Gadolinium chloride (GD) attenuates drug-induced hepatotoxicity by selectively inactivating Kupffer cells. The effect of GD was studied in reference to postnecrotic liver regeneration induced in rats by thioacetamide (TA). Rats, intravenously pretreated with a single dose of GD (0.1 mmol/Kg), were intraperitoneally injected with TA (6.6 mmol/Kg). Hepatocytes were isolated from rats at 0, 12, 24, 48, 72 and 96 h following TA intoxication, and samples of blood and liver were obtained. Parameters related to liver damage were determined in blood. In order to evaluate the mechanisms involved in the post-necrotic regenerative state, the time course of DNA distribution and ploidy were assayed in isolated hepatocytes. The levels of circulating cytokine TNFα was assayed in serum samples. TNFα was also determined by RT-PCR in liver extracts. The results showed that GD significantly reduced the extent of necrosis. The effect of GD induced noticeable changes in the post-necrotic regeneration, causing an increased percentage of hepatocytes in S phase of the cell cycle. Hepatocytes increased their proliferation as a result of these changes. TNFα expression and serum level were diminished in rats pretreated with GD. Thus, GD pre-treatment reduced TA-induced liver injury and accelerated postnecrotic liver regeneration. No evidence of TNFα implication in this enhancement of hepatocyte proliferation and liver regeneration was found. These results demonstrate that Kupffer cells are involved in TA-induced liver damage, as well as and also in the postnecrotic proliferative liver states

Evaluation of the performance of message routing protocols in delay tolerant networks (DTN) in Colombian scenario

Certain vehicles need to send information to their monitoring stations constantly, this information is usually sent by the vehicles, through the cellular network. The use of these wireless networks depends on coverage that it is not usually available in all geographic areas. This is the case of road segments where the coverage of data service of cellular networks is partial or zero, making transmission impossible. A particular case is the roads between the municipality of Juan de Acosta and the city of Barranquilla in Atlántico department (Colombia). As a solution, Delay-Tolerant Networks (DTN) emerge, which allow the transmission of data to the monitoring stations when there is no cellular network coverage. In this work, a simulated evaluation of the performance of some message routing protocols for DTN is performed, in the Juan de Acosta – Barranquilla scenario. Using “The Opportunistic Networking Environment”, we determined the performance of these message routing protocols. The results show that the first contact message routing protocol, presents the highest rate of delivery messages (delivery rate) and the lowest delivery latency (delivery latency). In addition, the Spray and Wait protocol presents better results in System message overload (overhead) than the first one. The Opportunistic Networking Environment simulator, the performance of these message routing protocols was determined in this scenario. The results show that the Firstcontact message routing protocol presents the highest rate of delivery (deliveryrate) and the lowest delivery delay (deliverylatency). In addition, the Spray and Wait protocol has a better result in system overhead than the first one

The pharmaceutical solvent N-methyl-2-pyrollidone (NMP) attenuates inflammation through Krüppel-like factor 2 activation to reduce atherogenesis.

N-methyl-2-pyrrolidone (NMP) is a versatile water-miscible polar aprotic solvent. It is used as a drug solubilizer and penetration enhancer in human and animal, yet its bioactivity properties remain elusive. Here, we report that NMP is a bioactive anti-inflammatory compound well tolerated in vivo, that shows efficacy in reducing disease in a mouse model of atherosclerosis. Mechanistically, NMP increases the expression of the transcription factor Kruppel-like factor 2 (KLF2). Monocytes and endothelial cells treated with NMP express increased levels of KLF2, produce less pro-inflammatory cytokines and adhesion molecules. We found that NMP attenuates monocyte adhesion to endothelial cells inflamed with tumor necrosis factor alpha (TNF-α) by reducing expression of adhesion molecules. We further show using KLF2 shRNA that the inhibitory effect of NMP on endothelial inflammation and subsequent monocyte adhesion is KLF2 dependent. Enhancing KLF2 expression and activity improves endothelial function, controls multiple genes critical for inflammation, and prevents atherosclerosis. Our findings demonstrate a consistent effect of NMP upon KLF2 activation and inflammation, biological processes central to atherogenesis. Our data suggest that inclusion of bioactive solvent NMP in pharmaceutical compositions to treat inflammatory disorders might be beneficial and safe, in particular to treat diseases of the vascular system, such as atherosclerosis

Epigenetics modifications and Subclinical Atherosclerosis in Obstructive Sleep Apnea: The EPIOSA study.

Background Obstructive sleep apnea (OSA) is associated with increased risk for cardiovascular morbidity and mortality. Epidemiological and animal models studies generate hypotheses for innovative strategies in OSA management by interferig intermediates mechanisms associated with cardiovascular complications. We have thus initiated the Epigenetics modification in Obstructive Sleep Apnea (EPIOSA) study (ClinicalTrials.gov identifier: NCT02131610). Methods/design EPIOSA is a prospective cohort study aiming to recruit 350 participants of caucasian ethnicity and free of other chronic or inflammatory diseases: 300 patients with prevalent OSA and 50 non-OSA subjects. All of them will be follow-up for at least 5 years. Recruitment and study visits are performed in single University-based sleep clinic using standard operating procedures. At baseline and at each one year follow-up examination, patients are subjected to a core phenotyping protocol. This includes a standardized questionnaire and physical examination to determine incident comorbidities and health resources utilization, with a primary focus on cardiovascular events. Confirmatory outcomes information is requested from patient records and the regional Department of Health Services. Every year, OSA status will be assessed by full sleep study and blood samples will be obtained for immediate standard biochemistry, hematology, inflammatory cytokines and cytometry analysis. For biobanking, aliquots of serum, plasma, urine, mRNA and DNA are also obtained. Bilateral carotid echography will be performed to assess subclinical atherosclerosis and atherosclerosis progression. OSA patients are treated according with national guidelines. Discussion EPIOSA will enable the prospective evaluation of inflammatory and epigenetics mechanism involved in cardiovascular complication of treated and non-treated patients with OSA compared with non OSA subjects