Self-aligned locally diffused emitter (SALDE) silicon solar cell

This paper presents, for the first time, a low-cost, high-throughput manufacturing approach for fabricating n-base dendritic web silicon solar cells with selectively doped emitters and self-aligned aluminum contacts using rapid thermal processing (RTP) and screen printing. The self-aligned locally diffused emitter (SALDE) structure is p⁺ nn⁺⁺ where aluminum is screen-printed on a boron-doped emitter and fired in a belt furnace to form a deep self-doped p⁺-layer and a self-aligned positive contact to the emitter according to the well-known aluminum-silicon (Al---Si) alloying process. The SALDE structure preserves the shallow emitter (20.2 μm) everywhere except directly beneath the emitter contact. There the junction depth is greater than 5 μm, as desired, in order to shield carriers in the bulk silicon from that part of the silicon surface covered by metal where the recombination rate is high. This structure is realized by using n-base (rather than p-base) substrates and by utilizing screen-printed aluminum (rather than silver) emitter contacts. Prototype dendritic web silicon (web) cells (25 cm² area) with efficiencies up to 13.2% have been produced.     

Biodegradation of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by Phanerochaete chrysosporium: new insight into the degradation pathway

Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is a recalcitrant energetic chemical that tends to accumulate in soil, close to the surface. The present study describes the aerobic biodegradability of HMX using Phanerochaete chrysosporium. When added to 7 day old static P. chrysosporium liquid cultures, HMX (600 nmol) degraded within 25 days of incubation. The removal of HMX was concomitant with the formation of transient amounts of its mono-nitroso derivative (1-NO-HMX). The latter apparently degraded via two potential routes: the first involved N-denitration followed by hydrolytic ring cleavage, and the second involved alpha-hydroxylation prior to ring cleavage. The degradation of 1-NO-HMX gave the ring-cleavage product 4-nitro-2,4-diazabutanal (NDAB), nitrite (NO2 -), nitrous oxide (N2O), and formaldehyde (HCHO). Using [14C]-HMX, we obtained 14CO2 (70% in 50 days), representing three C atoms of HMX. Incubation of real soils, contaminated with either HMX (403 micromol kg(-1)) (military base soil) or HMX (3057 micromol kg(-1)), and RDX (342 micromol kg(-1)) (ammunition soil) with the fungus led to 75 and 19.8% mineralization of HMX (liberated 14CO2), respectively, also via the intermediary formation of 1-NO-HMX. Mineralization in the latter soil increased to 35% after the addition of glucose, indicating that a fungus-based remediation process for heavily contaminated soils is promising. The present findings improve our understanding about the degradation pathway of HMX and demonstrate the utility of using the robust and versatile fungus P. chrysosporium to develop effective remediation processes for the removal of HMX.     

Dynamics of chromosome spreading

Consistency of optimum chromosome spreading during harvest of cytogenetic specimens remains a major concern. We have tested the idea that a precise control of the drying rate (the time with which metaphase cells dry), as fixed cell suspension is placed on a slide or an in situ culture in last fixation, may be the answer. Amniocyte and lymphocyte cultures were allowed to dry at defined combinations of relative humidity (RH) and temperature (T) in a modified Thermotron environmental control unit. We were able to demonstrate, based on 2,250 amniocytes and 1,650 lymphocytes, that the metaphase area after drying was a function of RH and T for both in situ and non-in situ culture systems. As the RH and T increase, the metaphase area increases until a threshold is reached. Also, as RH increases, the slide drying time increases. Data obtained using a response surface regression, proportional hazards regression analysis and slide drying time studies are consistent with our model of chromosome spreading. Optimum metaphase areas can be achieved at various combinations of RH and T. We propose that the use of an environmental control unit is a practical way of achieving optimum chromosome spreading routinely and in a highly consistent manner.     

Biodegradation of RDX and MNX with Rhodococcus sp. strain DN22: new insights into the degradation pathway

Previously we demonstrated that Rhodococcus sp. strain DN22 can degrade RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) aerobically via initial denitration. The present study describes the role of oxygen and water in the key denitration step leading to RDX decomposition using (18)O(2) and H(2)(18)O labeling experiments. We also investigated degradation of MNX (hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine) with DN22 under similar conditions. DN22 degraded RDX and MNX giving NO(2)(-), NO(3)(-), NDAB (4-nitro-diazabutanal), NH(3), N(2)O, and HCHO with NO(2)(-)/NO(3)(-) molar ratio reaching 17 and ca. 2, respectively. In the presence of (18)O(2), DN22 degraded RDX and produced NO(2)(-) with m/z at 46 Da that subsequently oxidized to NO(3)(-) containing one (18)O atom, but in the presence of H(2)(18)O we detected NO(3)(-) without (18)O. A control containing NO(2)(-), DN22, and (18)O(2) gave NO(3)(-) with one (18)O, confirming biotic oxidation of NO(2)(-) to NO(3)(-). Treatment of MNX with DN22 and (18)O(2) produced NO(3)(-) with two mass ions, one (66 Da) incorporating two (18)O atoms and another (64 Da) incorporating only one (18)O atom and we attributed their formation to bio-oxidation of the initially formed NO and NO(2)(-), respectively. In the presence of H(2)(18)O we detected NO(2)(-) with two different masses, one representing NO(2)(-) (46 Da) and another representing NO(2)(-) (48 Da) with the inclusion of one (18)O atom suggesting auto-oxidation of NO to NO(2)(-). Results indicated that denitration of either RDX or MNX and denitrosation of MNX by DN22 did not involve direct participation of either oxygen or water, but both played major roles in subsequent secondary chemical and biochemical reactions of NO and NO(2)(-).     

The effect of nanoparticles on wettability alteration for enhanced oil recovery: micromodel experimental studies and CFD simulation

The applications of nanotechnology in oilfields have attracted the attention of researchers to nanofluid injection as a novel approach for enhanced oil recovery. To better understand the prevailing mechanisms in such new displacement scenarios, micromodel experiments provide powerful tools to visually observe the way that nanoparticles may mobilize the trapped oil. In this work, the effect of silicon oxide nanoparticles on the alteration of wettability of glass micromodels was investigated in both experimental and numerical simulation approaches. The displacement experiments were performed on the original water-wet and imposed oil-wet (after aging in stearic acid/n-heptane solution) glass micromodels. The results of injection of nanofluids into the oil-saturated micromodels were then compared with those of the water injection scenarios. The flooding scenarios in the micromodels were also simulated numerically with the computational fluid dynamics (CFD) method. A good agreement between the experimental and simulation results was observed. An increase of 9% and 13% in the oil recovery was obtained by nanofluid flooding in experimental tests and CFD calculations, respectively.     

Self-healing semi-IPN materials from epoxy resin by solvent-free furan–maleimide Diels–Alder polymerization

Novel self-healing Diels–Alder (DA) polymer and the corresponding semi-interpenetrated polymer networks (semi-IPNs) were synthesized and characterized. Initially, a furan-functionalized resin (FFR) was synthesized through the ring-opening reaction of a conventional epoxy resin [diglycidyl ether bisphenol A (DGEBA)] with furfuryl alcohol as a bio-based compound. Subsequently, semi-IPNs with different compositions were obtained through the blending of DGEBA, FFR, 4,4′-diaminodiphenylmethane, and 1,1′-(methylenedi-1,4-phenylene) bismaleimide in the molten state by following a predetermined time–temperature program. Fourier transform infrared and nuclear magnetic resonance analyses confirmed the successful synthesis of the materials. Thermoreversibility via retro-DA (rDA) reaction was evidenced by differential scanning calorimetry (DSC) and sol–gel transition tests. Repeated DSC cycle was successfully performed thrice on the DA polyadduct which corroborated repeatability of the DA/rDA association/dissociation. Self-healing and mechanical properties were preliminarily evaluated by scanning electronic microscopy and flexural testing analyses, respectively. The self-healing efficiencies were around 80 and 95% for semi-IPN and DA polyadduct, respectively, based on flexural strength. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48015.     

Image captioning improved visual question answering

Multimedia Tools and Applications - Both Visual Question Answering (VQA) and image captioning are the problems which involve Computer Vision (CV) and Natural Language Processing (NLP) domains. In...     

Reflecting on the preparation of guidelines for strategic environmental assessment (SEA) of nuclear power programmes

In this paper, the ‘guidelines for strategic environmental assessment (SEA) of nuclear power programmes’ by the International Atomic Energy Agency are introduced. This includes a reflection on their preparation process and contents as well as consultation feedback. The preparation process started with two meetings of international nuclear and SEA experts and the creation of a writing team which prepared an initial set of draft guidelines. This was followed by various consultation exercises. The guidelines are organised along an allocation of tasks within a tiered system of energy related policies, plans, programmes and projects. Whilst consultation showed that there was agreement on the approach to most issues, no consensus was present on the extent to which economic and social issues should be fully integrated with environmental considerations. Strong support was given to the way quality review is designed, going beyond focusing on the main SEA reports to cover procedural and participatory aspects next to elements of a comprehensively tiered decision making framework, the ability to influence decisions as well as the quality (expertise and experience) of those involved in conducting the SEA.

Abbreviation: SEA: Strategic Environmental Assessment; EIA: Environmental Impact Assessment; IAEA: International Atomic Energy Agency     

Tweet and user validation with supervised feature ranking and rumor classification

Multimedia Tools and Applications - Filtering fake news from social network posts and detecting social network users who are responsible for generating and propagating these rumors have become two...