A study of ignition phenomena of bulk metals by radiant heating

Early research on combustion of metals was motivated by the knowledge of the large heat release and corresponding high temperatures associated with metal-oxygen reactions. The advent of space flight brought about an increased interest in the ignition and combustion of metallic particles as additives in solid rocket propellants. More recently, attention has been given to the flammability properties of bulk, structural metals due to the number of accidental explosions of metal components in high-pressure oxygen systems. The following work represents a preliminary study that is part of a broader research effort aimed at providing further insight into the phenomena of bulk metal combustion by looking at the effects of gravity on the ignition behavior of metals. The scope of this preliminary experimental study includes the use of a non-coherent, continuous radiation ignition source, the measurement of temperature profiles of a variety of metals and a qualitative observation of the ignition phenomena at normal gravity. The specific objectives of the investigation include: (1) a feasibility study of the use of a continuous radiation source for metal ignition; (2) testing and characterization of the ignition behavior of a variety of metals; and (3) building a preliminary experimental database on ignition of metals under normal gravity conditions

Ectopic pregnancy after assisted reproductive technology: a retrospective study

In this study from 2006 to 2010,1628 IVF-ET cycles were performed in our unit. Long protocol with GnRH agonist plus recombinant FSH, short protocol with GnRH antagonist, short protocol with microdoses of GnRH agonist (flare up), natural modified cycle with GnRH antagonist and hCG were applied. The serum level of the P-hCG was measured 12 days after embryotransfer (ET). When positive, the P-hCG level was determined every 4 days until the ultrasound examination 22 days after the ET. From 1628 IVF - ET cycles, we had 10 tubal pregnancies (0,61%) and one heterotopic pregnancy (HP). Salpingectomy was performed in all patients, 7 had laparoscopy, and 3 underwent emergent laparotomy due to hemorrhagic shock. Regarding the HP patient, an ultrasound scan confirmed a viable intrauterine 8-weeks gestation and an ectopic pregnancy (EP) in the left tube with fetal heartbeat corresponding to gestational age of 7-8 weeks. Laparoscopy with left salpingectomy was performed the following day. The intrauterine pregnancy proceeded uneventfully. The patient delivered by elective Cesarean section at 39 weeks of gestation due to breech presentation. Patients undergoing IVF-ET must be informed of the risk of EP and the possibility of HP should not be ignored

Ignition and Combustion of Bulk Metals in a Microgravity Environment

This annual report summarizes the latest results obtained in a NASA-supported project to investigate the effect of gravity on the ignition and combustion of bulk metals. The experimental arrangement used for this purpose consists of a 1000-W xenon lamp that irradiates the top surface of cylindrical titanium and magnesium specimens, 4 mm in diameter and 4 mm in height, in a quiescent, pure-oxygen environment at 1 atm. Reduced gravity is obtained from the NASA LeRC DC-9 aircraft flying parabolic trajectories. Values of critical and ignition temperatures are obtained from thermocouple records. Qualitative observations and propagation rates are extracted from high-speed cinematography. Emission spectra of gas-phase reactions are obtained with an imaging spectrograph/diode array system. It was found that high applied heating rates and large internal conduction losses generate critical and ignition temperatures that are several hundred degrees above the values obtained from isothermal experiments. Because of high conduction and radiation heat losses, no appreciable effect on ignition temperatures with reduced convection in low gravity is detected. Lower propagation rates of the molten interface on titanium and of ignition waves on magnesium are obtained at reduced gravity. These rates are compared to theoretical results from heat conduction analyses with a diffusion/convection controlled reaction. The close agreement found between experimental and theoretical values indicates the importance of the influence of natural convection-enhanced oxygen transport on combustion rates. Lower oxygen flux and lack of oxide product removal in the absence of convective currents appear to be responsible for longer burning times of magnesium diffusion flames at reduced gravity. The accumulation of condensed oxide particles in the flame front at low gravity produces a previously unreported unsteady explosion phenomenon in bulk magnesium flames. This spherically symmetric explosion phenomenon seems to be driven by increased radiation heat transfer from the flame front to an evaporating metal core covered by a porous, flexible oxide coating. These important results have revealed the significant role of gravity on the burning of metals, and are now being used as the database for future experiments to be conducted with different metals at various pressures, oxygen concentrations and gravity levels

Attentional requirements of walking according to the gait phase and onset of auditory stimuli

The influence of an attention demanding cognitive task on each phase of gait was analyzed, using a dual-task paradigm. Electromyography (iEMG) from eight muscles from the dominant leg was collected from 23 participants (age 18-27) while walking on a treadmill at a 20% increase of their self-selected speed and while walking and performing a cognitive task. The cognitive task consisted of subtracting one (EASY) or seven (HARD) from numbers aurally presented. Reaction time (RT) and accurate responses of the cognitive task were recorded. iEMG events were selected according to stimuli onset (0-150 ms, 150-300 ms and 300-450 ms) prior to the phases of gait (double-leg, single- leg and swing). There was a decrease in iEMG amplitude of fibularis longus (p = .013) and vastus lateralis (p = .065) while walking and performing the cognitive task. When stimulus onset was considered, iEMG of medial gastrocnemius (p = .021) and lateral gastrocnemius (p = .004) were reduced during single-leg stance, when stimuli occurred between 300-450 ms prior to this phase. Participants committed more errors and had longer RT on the HARD task. RT was longer when subtracting while walking in comparison to subtracting alone. Young adults expressed dual-task cost in the motor and the cognitive tasks, suggesting that walking requires attention. There was a specific moment (300 ms after stimulus onset) during single-leg stance that dual-task cost occurred. Reasons for this interference and the implications of a reduction in iEMG while walking and performing an attention demanding cognitive task are discussed

Ignition and Combustion Characteristics of Pure Bulk Metals: Normal-Gravity Test Results

An experimental apparatus has been designed for the study of bulk metal ignition under elevated, normal and reduced gravity environments. The present work describes the technical characteristics of the system, the analytical techniques employed, the results obtained from the ignition of a variety of metals subjected to normal gravity conditions and the first results obtained from experiments under elevated gravity. A 1000 W xenon short-arc lamp is used to irradiate the top surface of a cylindrical metal specimen 4 mm in diameter and 4 mm high in a quiescent pure-oxygen environment at 0.1 MPa. Iron, titanium, zirconium, magnesium, zinc, tin, and copper specimens are investigated. All these metals exhibit ignition and combustion behavior varying in strength and speed. Values of ignition temperatures below, above or in the range of the metal melting point are obtained from the temperature records. The emission spectra from the magnesium-oxygen gas-phase reaction reveals the dynamic evolution of the ignition event. Scanning electron microscope and x-ray spectroscopic analysis provide the sequence of oxide formation on the burning of copper samples. Preliminary results on the effect of higher-than-normal gravity levels on the ignition of titanium specimens is presented

Spectroscopic ellipsometry studies of HF treated Si (100) surfaces

Both ex situ and in situ spectroscopic ellipsometry (SE) measurements were employed to investigate the effects of HF cleaning on Si surfaces. The hydrogen-terminated (H-terminated) Si surface was modeled as an equivalent dielectric layer, and monitored in real time by SE measurements. The SE analyses indicate that after a 20-s 9:1 HF dip without rinse, the Si(100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si(100) surface was observed, in an ultrahigh vacuum (UHV) chamber, and analyzed by the in situ SE. Evidence for desorption of the H-terminated Si surface-layer, after being heated to approximately 550 C in the UHV chamber, is presented and discussed. This is the first use of an ex situ and in situ real-time, nondestructive technique capable of showing state of passivation, the rate of reoxidation, and the surface roughness of the H-terminated Si surfaces

Cholesteryl Hemiazelate Present in Cardiovascular Disease Patients Causes Lysosome Dysfunction in Murine Fibroblasts

Funding Information: This work was financially supported by the FCT (Foundation for Science and Technology of the Portuguese Ministry of Science and Higher Education), Refs. 2022.01305.PTDC and 2022.03249.PTDC. The Coimbra Chemistry Centre (CQC) is supported by the FCT through projects UIDB/00313/2020 and UIDP/00313/2020. E.L. is the holder of a PhD fellowship from the FCT (2021.06265.BD). A.R.A.M. was funded by the FCT Stimulus of Scientific Employment Individual Support Call 2017 (CEECIND/01006/2017). R.P. was funded by the NHLBI Division of Intramural Research (ZIA HL006151-10). Publisher Copyright: © 2023 by the authors.There is growing evidence supporting the role of fibroblasts in all stages of atherosclerosis, from the initial phase to fibrous cap and plaque formation. In the arterial wall, as with macrophages and vascular smooth muscle cells, fibroblasts are exposed to a myriad of LDL lipids, including the lipid species formed during the oxidation of their polyunsaturated fatty acids of cholesteryl esters (PUFA-CEs). Recently, our group identified the final oxidation products of the PUFA-CEs, cholesteryl hemiesters (ChE), in tissues from cardiovascular disease patients. Cholesteryl hemiazelate (ChA), the most prevalent lipid of this family, is sufficient to impact lysosome function in macrophages and vascular smooth muscle cells, with consequences for their homeostasis. Here, we show that the lysosomal compartment of ChA-treated fibroblasts also becomes dysfunctional. Indeed, fibroblasts exposed to ChA exhibited a perinuclear accumulation of enlarged lysosomes full of neutral lipids. However, this outcome did not trigger de novo lysosome biogenesis, and only the lysosomal transcription factor E3 (TFE3) was slightly transcriptionally upregulated. As a consequence, autophagy was inhibited, probably via mTORC1 activation, culminating in fibroblasts’ apoptosis. Our findings suggest that the impairment of lysosome function and autophagy and the induction of apoptosis in fibroblasts may represent an additional mechanism by which ChA can contribute to the progression of atherosclerosis.publishersversionpublishe

Autoimmune/inflammatory syndrome induced by adjuvants: a review

The autoimmune/inflammatory syndrome induced by adjuvants (ASIA) includes several autoimmune conditions and phenomena that occur after exposure to substances with adjuvant activity. The spectrum of the disease is heterogeneous with respect to the clinical presentation as well as the severity of the clinical manifestations. Different substances and medical devices with adjuvant activity are currently known, such as vaccines, oils, silicones, mineral salts, lipopolysaccharides, peptidoglycans, among others. These adjuvants are immunological molecules that function through potentiation of antigen-specific immune responses. Thus, the etiopathogenesis of ASIA syndrome involves a multifactorial interaction between environmental factors and genetic predisposition, and secondary activation of the adaptive and innate arms of the immune system through various mechanisms. Although in some reported cases the ASIA syndrome improves considerably when removing the implants, there are no conclusive results for the clinical benefit of removing the implants, so it is necessary to carry out further basic, clinical and surgical investigations in order to determine the best therapeutic decision