Combustion of Gaseous Fuels Under Reduced-Gravity Conditions

The need for an improved understanding of fires is becoming critically important with increased space travel and utilization. While the control of fires in low-gravity environments is not well understood, it is known that buoyancy significantly affects flame behavior and characteristics. The objective of this research is to gain a more fundamental understanding of fires, and to quantify flame behavior under reduced-gravity levels. Non-premixed flames of gaseous fuels are considered in this study because they are relatively simple and easy to control, yet embody mechanisms found in all types of combustion processes ranging from uncontrolled fires to practical combustion systems. This paper presents some recent results from microgravity studies of these flames. In addition, the potential usefulness of lunar- and Martian-based laboratories is discussed in order to understand the characteristics and behavior of fires in reduced-gravity environments

Effects of buoyancy on gas jet diffusion flames

The objective of this effort was to gain a better understanding of the fundamental phenomena involved in laminar gas jet diffusion flames in the absence of buoyancy by studying the transient phenomena of ignition and flame development, (quasi-) steady-state flame characteristics, soot effects, radiation, and, if any, extinction phenomena. This involved measurements of flame size and development, as well as temperature and radiation. Additionally, flame behavior, color, and luminosity were observed and recorded. The tests quantified the effects of Reynolds number, nozzle size, fuel reactivity and type, oxygen concentration, and pressure on flame characteristics. Analytical and numerical modeling efforts were also performed. Methane and propane flames were studied in the 2.2 Second Drop Tower and the 5.18-Second Zero-Gravity Facility of NASA LeRC. In addition, a preliminary series of tests were conducted in the KC-135 research aircraft. Both micro-gravity and normal-gravity flames were studied in this program. The results have provided unique and new information on the behavior and characteristics of gas jet diffusion flames in micro-gravity environments

Effects of Buoyancy on Laminar, Transitional, and Turbulent Gas Jet Diffusion Flames

Gas jet diffusion flames have been a subject of research for many years. However, a better understanding of the physical and chemical phenomena occurring in these flames is still needed, and, while the effects of gravity on the burning process have been observed, the basic mechanisms responsible for these changes have yet to be determined. The fundamental mechanisms that control the combustion process are in general coupled and quite complicated. These include mixing, radiation, kinetics, soot formation and disposition, inertia, diffusion, and viscous effects. In order to understand the mechanisms controlling a fire, laboratory-scale laminar and turbulent gas-jet diffusion flames have been extensively studied, which have provided important information in relation to the physico-chemical processes occurring in flames. However, turbulent flames are not fully understood and their understanding requires more fundamental studies of laminar diffusion flames in which the interplay of transport phenomena and chemical kinetics is more tractable. But even this basic, relatively simple flame is not completely characterized in relation to soot formation, radiation, diffusion, and kinetics. Therefore, gaining an understanding of laminar flames is essential to the understanding of turbulent flames, and particularly fires, in which the same basic phenomena occur. In order to improve and verify the theoretical models essential to the interpretation of data, the complexity and degree of coupling of the controlling mechanisms must be reduced. If gravity is isolated, the complication of buoyancy-induced convection would be removed from the problem. In addition, buoyant convection in normal gravity masks the effects of other controlling parameters on the flame. Therefore, the combination of normal-gravity and microgravity data would provide the information, both theoretical and experimental, to improve our understanding of diffusion flames in general, and the effects of gravity on the burning process in particular

Estimation of Nursing Staff in Selected Hospitals of Ilam and Ahvaz Provinces, Western Iran

Background: The nurses as the largest group among different groups of hospital workforce play a crucial role in success of the hospital activities and promotion of community health. Objectives: This study aimed to obtain an estimation of the necessary nursing workforce status in educational hospitals affiliated to Ilam and Ahvaz University of Medical Sciences based on the scientific formula. Materials and Methods: This research was a cross sectional-descriptive study, which was done in hospitals affiliated to Ilam and Ahvaz University of Medical Sciences during 2010. Using three researcher-made forms, data was collected from all clinical, para-clinical, financial, administrative and support departments of hospitals. Data was analyzed in accordance to the standards of Iran's Ministry of Health and Medical Education using the Excel software. Results: The results showed that the nursing staffs in the 42 wards (89.5 %) were lower than the standards, only one ward (2 %) matched the standards and the rest of the wards (8.5%) were higher than the standards. The organizational dislocation (utilization of nurses in non-related jobs) of nursing staffs obtained for Imam Khomeini of Ilam, Mostafa Khomeini, Taleghani, Razi and Imam Khomeini of Ahvaz Hospitals were 8, 5, 3, 8 and 21, respectively. Conclusion: Generally, the studied hospitals were faced with a lack of nursing manpower and distribution of manpower was not appropriate. Proper planning and management of manpower in accordance with the lack of personnel, compensates and achieves the standards required for hospital’s nursing manpower and this would lead to an increase in the efficiency of hospitals activities and can provide satisfaction for the nursing staff

Stabilization of Sand with Colloidal Nano-Silica Hydrosols

Colloidal nano-silica (NS) hydrosols are electrochemically stabilized, polymerized amorphous silica in low viscosity solutions, and in the form of hydrated gels, silica globules or pellicles. Compared to applications in concrete technology, the use of silica-based binders for groundwork applications has received little attention. Silica-based hydrosols impose no known direct risks to humans and are generally courteous to the soil health and ecosystem service functions. Their localized impact on microorganisms however needs to be further investigated. To this end, NS hydrosols have a scope for use as an alternative low-viscose material in groundworks. The current understanding of interactions between NS hydrosols and soil (sand) is, however, confused by the limited availability of experimental evidence concerning undrained static flow and large strain behavior. The contributions, presented in this paper, advance the knowledge through experimental testing, molecular modelling, and micro-analytical measurements. Four grades of colloidal NS (1–15 wt.%) were synthesized for grouting medium-dense sub-angular fine siliceous sand specimens. Consolidated-undrained triaxial compression testing was performed on the base and treated sand for isotropic consolidation over the effective stress range 100–400 kPa. Overall, silica impregnation produced improvements in yield and residual undrained shear strengths, restricted unwelcomed impacts of excess pore water pressure, and led to the formation of generally more dilative, strain-hardening behavior. Steady states and static flow potential indices are also studied as functions of confinement level and viscosity of the NS grout

research article

During embryonic development and tissue homeostasis, reproducible proportions of differentiated cell types are specified from populations of multipotent precursor cells. Molecular mechanisms that enable both robust cell-type proportioning despite variable initial conditions in the precursor cells, and the re-establishment of these proportions upon perturbations in a developing tissue remain to be characterized. Here, we report that the differentiation of robust proportions of epiblast-like and primitive endoderm-like cells in mouse embryonic stem cell cultures emerges at the population level through cell-cell communication via a short-range fibroblast growth factor 4 (FGF4) signal. We characterize the molecular and dynamical properties of the communication mechanism and show how it controls both robust cell-type proportioning from a wide range of experimentally controlled initial conditions, as well as the autonomous re-establishment of these proportions following the isolation of one cell type. The generation and maintenance of reproducible proportions of discrete cell types is a new function for FGF signaling that might operate in a range of developing tissues

Psychometric properties and measurement invariance across gender of the Compulsive Online Shopping Scale (COSS) among Iranians.

The present study aimed to investigate the psychometric properties and measurement invariance of the Compulsive Online Shopping Scale (COSS) in an Iranian population. The total sample of 802 participants (257 females; Mean age = 22.27, SD = 2.83) were selected via convenience sampling from Tehran, Iran. Confirmatory Factor Analysis supported the 7-factor structure of the COSS as proposed in the original study. The measurement invariance found in this study suggests that the COSS provides sufficiently unbiased use among males and females. The current findings also support the concurrent validity of the Persian COSS, which exhibited positive and significant associations with loneliness, impulsivity, obsession, internalized symptoms, and Internet use. Furthermore, results confirm the convergent validity of the Persian COSS and showcased acceptable internal consistency for all factors, and the total score. The findings of the present study indicate that compulsive online shopping could be assessed adequately in Iranian samples using the COSS. [Abstract copyright: Crown Copyright © 2023 Published by Elsevier Ltd.

All-optical switching using a new photonic crystal directional coupler

In this paper all-optical switching in a new photonic crystal directional coupler is performed.  The structure of the switch consists of a directional coupler and a separate path for a control signal called “control waveguide”. In contrast to the former reported structures in which the directional couplers are made by removing a row of rods entirely, the directional coupler in our optical switch is constructed by two reduced-radius line-defect waveguides separated by the control waveguide. Furthermore, in our case the background material has the nonlinear Kerr property. Therefore, in the structure of this work, no frequency overlap occurs between the control waveguide mode and the directional coupler modes. It is shown that such a condition provides a very good isolation between the control and the probe signals at the output ports. In the control waveguide, nonlinear Kerr effect causes the required refractive index change by the presence of a high power control (pump) signal. Even and odd modes of the coupler are investigated by applying the distribution of the refractive index change in the nonlinear region of a super-cell so that a switching length of about 94 µm is obtained at the wavelength of 1.55 µm. Finally, all-optical switching of the 1.55 µm probe signal using a control signal at the wavelength of 1.3 µm, is simulated through the finite-difference time-domain method, where both signals are desirable in optical communication systems. A very high extinction ratio of 67 dB is achieved and the temporal characteristics of the switch are demonstrated

Epidemiological Aspects of Canine Dirofilariasis in the North of Iran

Background: Dirofilaria immitis is an important parasite in dog and other carnivores. Our objec­tive was study on incidence and periodicity of heartworm in north of Iran and using other meth­ods for its diagnosis in addition to Parasitology exam.Methods: This survey spanned two years, between 2006 and 2008. Blood samples were collected from 431 stray dogs distributed along north of Iran, the coastal areas of the Caspian Sea. The Knott's modified test was used for diagnosis of D. immitis and other filariae. Meanwhile, the periodic­ity of microfilaria in peripheral blood circulation was calculated and the imaging diagno­sis techniques of four dogs that had positive results were done.Result: Diagnostic parasitology results indicated that 16.01% of stray dogs were microfilaremic. Two different microfilariae were diagnosed: D. immitis in 13.69%, Dipetalonema reconditum in 1.86% and in 0.46% both of them. There was no statistically significant between infection to fiariae with sex and age of dogs. Also study on the periodicity of the presence of microfilaria in peripheral circulation showed that the highest rate of those was at 1 am and the lowest rate at 12 pm. Radiographic study showed distinctive signs with varied degrees of severity included: Tortu­ous and enlargement of main and lobar pulmonary artery, pulmonary parenchymal lesions and Right side heart enlargement that confirmed in electrocardiography. Also in echocardiographic images observed short parallel-sided images with the appearance of equal signs that indicated the pres­ence of the heartworm.Conclusion: These results showed that to obtain a reliable diagnosis of heartworm infection, imag­ing tests could support parasitological exams