Periodic Exposure of Plasma-Activated Medium Alters Fibroblast Cellular Homoeostasis

Excess amounts of redox stress and failure to regulate homeostatic levels of reactive species are associated with several skin pathophysiologic conditions. Nonmalignant cells are assumed to cope better with higher reactive oxygen and nitrogen species (RONS) levels. However, the effect of periodic stress on this balance has not been investigated in fibroblasts in the field of plasma medicine. In this study, we aimed to investigate intrinsic changes with respect to cellular proliferation, cell cycle, and ability to neutralize the redox stress inside fibroblast cells following periodic redox stress in vitro. Soft jet plasma with air as feeding gas was used to generate plasma-activated medium (PAM) for inducing redox stress conditions. We assessed cellular viability, energetics, and cell cycle machinery under oxidative stress conditions at weeks 3, 6, 9, and 12. Fibroblasts retained their usual physiological properties until 6 weeks. Fibroblasts failed to overcome the redox stress induced by periodic PAM exposure after 6 weeks, indicating its threshold potential. Periodic stress above the threshold level led to alterations in fibroblast cellular processes. These include consistent increases in apoptosis, while RONS accumulation and cell cycle arrest were observed at the final stages. Currently, the use of NTP in clinical settings is limited due to a lack of knowledge about fibroblasts’ behavior in wound healing, scar formation, and other fibrotic disorders. Understanding fibroblasts’ physiology could help to utilize nonthermal plasma in redox-related skin diseases. Furthermore, these results provide new information about the threshold capacity of fibroblasts and an insight into the adaptation mechanism against periodic oxidative stress conditions in fibroblasts.     

Considering the fault dependency concept with debugging time lag in software reliability growth modeling using a power function of testing time

Since the early 1970s tremendous growth has been seen in the research of software reliability growth modeling.In general, software reliability growth models (SRGMs) are applicable to the late stages of testing in software development and they can provide useful information about how to improve the reliability of software products.A number of SRGMs have been proposed in the literature to represent time-dependent fault identification/removal phenomenon;still new models are being proposed that could fit a greater number of reliability growth curves.Often,it is assumed that detected faults axe immediately corrected when mathematical models are developed.This assumption may not be realistic in practice because the time to remove a detected fault depends on the complexity of the fault,the skill and experience of the personnel,the size of the debugging team,the technique,and so on.Thus,the detected fault need not be immediately removed,and it may lag the fault detection process by a delay effect factor.In this paper,we first review how different software reliability growth models have been developed,where fault detection process is dependent not only on the number of residual fault content but also on the testing time,and see how these models can be reinterpreted as the delayed fault detection model by using a delay effect factor.Based on the power function of the testing time concept,we propose four new SRGMs that assume the presence of two types of faults in the software:leading and dependent faults.Leading faults are those that can be removed upon a failure being observed.However,dependent faults are masked by leading faults and can only be removed after the corresponding leading fault has been removed with a debugging time lag.These models have been tested on real software error data to show its goodness of fit,predictive validity and applicability.     

Revamp study of crude distillation unit heat exchanger network: Energy integration potential of delayed coking unit free hot streams

This work addresses the revamp study of the crude distillation unit (CDU) heat exchanger network (HEN) of a typical refinery with and without the consideration of the free hot streams available in the delayed coking unit (DCU). Based on pinch design method, two sub-cases of revamp study have been considered namely (a) installation of new heat exchangers for the entire network and (b) reutilization of existing heat exchangers. Based on the study, it has been evaluated that the revamp design of existing CDU HEN without considering the DCU free hot streams allows the enhancement of heat integration by 4.73% with respect to that available for the base case. On the other hand, the heat integration potential of DCU free hot streams is evaluated to enhance energy integration by 15.66% (with respect to the base case) with a simultaneous reduction of furnace duty by 37.1% and cooling water duties by 89.8%. Of various cases considered, the most attractive option corresponds to the partial revamp of CDU HEN along with DCU free hot streams that involve the reutilization of existing heat exchangers. The profitability analysis of this option concludes that the revamp design needs an additional investment of 2.68 M$ to enhance annual profit by 1.58 M$ with a payback period of 1.9 years. Thereby, the heat integration potential of DCU free hot streams is inferred to be significant and marks an important choice amongst different key revamp parameters associated to heat exchanger networks.     

Financing energy efficiency in developing countries—lessons learned and remaining challenges

Although energy efficiency implementation is increasingly being recognized by policymakers worldwide as one of the most effective means to mitigating rising energy prices, tackling potential environmental risks, and enhancing energy security, mainstreaming its financing in developing country markets continues to be a challenge. Experience shows that converting cost-effective energy savings potential, particularly the demand-side improvement opportunities across sectors, into investments face many barriers and unforeseen transaction costs. This paper draws upon selected experiences with financing energy efficiency in developing countries to explore the key factors of various programmatic approaches and financing instruments that have been applied successfully for delivering energy efficiency solutions. Through case studies, a diverse range of institutional issues are examined related to the identification, packaging, designing, and monitoring approaches that have been used to catalyze traditional and innovative financing of energy efficiency projects. With adequate liquidity in major developing country markets and availability of modern energy savings technologies, it is often the institutional issues that become a key challenge to address in order to finance and implement robust programs. As further operational experience is gained, increased knowledge sharing can lead to scaling-up of such energy efficiency investments. The paper concludes with some ideas for accelerating implementation.     

Engine knock and combustion characteristics of a spark ignition engine operating with varying hydrogen and carbon monoxide proportions

Varying proportions of hydrogen and carbon monoxide (synthesis gas) have been investigated as a spark ignition (SI) engine fuel in this paper. It is important to understand how various synthesis gas compositions effect important SI combustion fundamentals, such as knock and burn duration, because in synthesis gas production applications, the compositions can vary significantly depending on the feedstock and production method.A single cylinder cooperative fuels research (CFR) engine was used to investigate the knock and combustion characteristics of three blends of synthesis gas (H₂/CO ratio); 1) 100/0, 2) 75/25, and 3) 50/50, by volume. These blends were tested at three compression ratios (6:1, 8:1, and 10:1), and three equivalence ratios (0.6, 0.7, and 0.8).It was revealed that the knock limited compression ratio (KLCR) of a H₂/CO mixture increases with increasing CO fraction, for a given spark timing. For a given equivalence ratio and spark timing, a 50%/50% H₂/CO mixture produced a KLCR of 8:1 compared to a 100% H₂ condition, which produced a KLCR of 6:1. The burn duration and ignition lag is also increased with increasing CO fraction. The results from this work are important for those considering using synthesis gas as a fuel in SI engines. It reveals that although CO is a slow burning fuel, higher CO fractions in synthesis gas can be beneficial, because of its increased resistance to knock, which gives it the potential of producing higher indicated efficiencies through the utilization of an engine with a higher compression ratio.     

Turbulent natural convection in an enclosure with localized heating from below

This study reports the results of a numerical investigation of turbulent natural convection in a square enclosure with localized heating from below and symmetrical cooling from the vertical side walls. The present study simulates the case of an accidental heat generation due to fire in a typical isolated building of a nuclear reactor or electronic components cabin. The source of fire is considered to be centrally located at the bottom wall with different heated widths, which is assumed to be either isothermal or with isoflux. For the purpose of the analysis, the source length is varied from 20 to 80% of the total width of the bottom wall. The top wall and the unheated portion of the bottom wall are considered to be adiabatic, whereas sidewalls are isothermal. Steady as well as transient forms of two-dimensional Reynolds–Averaged-Navier–Stokes equations and conservation equations of mass and energy, coupled with the Boussinesq approximation, are solved by the control volume based discretisation method employing the SIMPLE algorithm for pressure–velocity coupling. Turbulence is modeled using the standard k–ε model. Rayleigh number, Ra, based on the enclosure height is varied from 10⁸ to 10¹². Stream lines and isotherms are presented for various combinations of Ra and the heated width. A double cell flow pattern is observed with marginal loss in symmetry as Ra increases. The results are reported in the form of local and average Nusselt number on the heated floor. Correlations are developed to predict the heat transfer rates from the enclosure as a function of dimensionless heated width of the bottom wall and Ra, by least square linear regression analysis.     

A new method of determination of series and shunt resistances of silicon solar cells

A new method of measurement of series resistance R_s and shunt resistance R_sh of a silicon solar cell is presented. The method is based on the single exponential model and utilizes the steady state illuminated I–V characteristics in third and fourth quadrants and the V_oc–I_sc characteristics of the cell. It enables determination of values of R_sh and R_s with the intensity of illumination. For determination of R_s it does not require R_sh to be assumed infinite and realistic values of R_sh can be used. The method is very convenient to use and in the present study it has been applied to silicon solar cells having finite values of R_sh. We have found that R_sh is independent of intensity but the R_s decreases with both the intensity of illumination and the junction voltage.     

Palladium dispersed multiwalled carbon nanotube based hydrogen sensor for fuel cell applications

Palladium nanocatalysts supported on surface-oxidized multiwalled carbon nanotubes (MWNT) were prepared by the aqueous solution reduction of _PdCl2${\mathrm{PdCl}}_2$. MWNT have been synthesized by catalytic chemical vapor deposition (CCVD) technique. Pyrolysis of acetylene using a fixed-bed catalytic reactor over rare earth (RE) based _AB2${\mathrm{AB}}_2$ alloy hydride catalyst, obtained through hydrogen decrepitation technique, has been performed to synthesize MWNT. Structural, morphological and vibrational characterizations have been carried out using XRD, SEM, TEM and Raman spectroscopy, respectively. In situ electrical resistance measurements for thin films of MWNT obtained by spin coating samples were carried out by two-probe technique in a chamber with provision to introduce known concentration of hydrogen in constant air flow. Investigations of hydrogen sensing properties of Pd–MWNT ensembles have been carried out. The stability of Pd–MWNT thin films after several cycles of adsorption and desorption was studied. The change in electrical resistance due to hydrogen adsorption is reversible, with increase to saturation on exposure to hydrogen gas. The results demonstrate that chemically treated MWNT functionalized with nanostructured Pd show good _H2${\mathrm{H}}_2$ sensing response at room temperature.     

Experimental and simulation studies on the effect of suction opening orientation on solar vertical chimney

The zero energy building considered is a single storey building in Tiruchirappalli city retrofitted with various green features. This study investigated the effect of a suction opening orientation on a vertical solar chimney (VSC), integrated into a one-storey building. It was designed, manufactured and tested through selection of different suction openings for the entry of air, including right, left, front, back, both right and left and both front and back sides. Genetic algorithm (GA) calculates maximum air flow rate for a building with VSC for better suction opening, in Tiruchirappalli's dry, environmental conditions. GA is a useful technique for finding an improved suction opening specifically in the presence of a host of independent parameters which are large. The obtained results are related to fluid flow temperature distribution along the chimney, mass flow rate and air change per hour. The findings between the GA and the experimental results show sound agreement.