Porous silicon in solar cells: A review and a description of its application as an AR coating

In this paper, we first review the potential applications of porous Si in solar cell structures. Then we describe the fabrication of this material by both electrochemical and chemical etching methods, providing some guidelines for a better comprehension of the influence of each process parameter. After that, the properties of porous Si in terms of morphology, structure, photoluminescence, and electroluminescence emissions are summarized together with their actual photovoltaic applications.The results of our study specifically address the creation of an antireflection (AR) coating for polycrystalline Si based solar cells. We have demonstrated the feasibility of a very efficient porous Si AR layer, prepared by a simple, cost effective, chemical etching method. The formation of a porous Si layer about 0.5 μm thick on the polycrystalline wafer results in an effective reflectance coefficient R_eff lower than 5% in the wavelength region from 350 to 1150 nm. The drastic reduction of the optical losses is controllable by the process parameters and is almost independent of the starting substrate.     

Experimental verification of fox and Li patterns in open resonators

An experiment with a microwave open resonator of the Fabry?Pérot type is described. The field distribution of the fundamental mode has been accurately determined. A very good agreement has been found with the distributions computed by Fox and Li. It has been verified that flatness and alignment requirements are extremely critical and can explain the well known difficulty of obtaining in practice the Fox and Li patterns.     

The role of wall deposition and re‐entrainment in swirl spray dryers

A new experimental method is outlined to study fouling in spray dryers and similar devices. In essence, it makes the deposits traceable so that one can quantify the material that comes off the walls, how long it remains there and how the deposits agglomerate with particles in the air. This paper investigates a countercurrent swirl spray dryer of detergent and provides sound evidence that fouling is a dynamic process: clusters form and break at the walls renewing an active layer of deposits. Remarkably, the wall generates >20% of the product and most of the large granules, and increases drastically the residence time of the powder. The assumptions of current numerical models are clearly invalid (i.e. particles rebound at the wall or deposit indefinitely). Several re‐entrainment mechanisms and their times scales are identified in this work, and accordingly, a new general framework to describe fouling in spray dryers is proposed. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1804–1821, 2015     

Fatty acid and sensory profiles of Caciocavallo cheese as affected by management system

The effect of season of the year associated with changes in feeding and management system (pasture-based vs. confinement) on milk and cheese fatty acid profile and on sensory properties of Caciocavallo cheese was evaluated on 3 mountain dairy farms. Each farm used a pasture-based feeding system from April to June and from September to October (PS), and a confinement system for the rest of the year (CS). As a consequence of grazing, PS milk showed higher percentages of C18:3, cis-9,trans-11 conjugated linoleic acid, and trans-11 C18:1, and a reduced percentage of C16:0. The fatty acid profile of cheese largely reflected that of the corresponding raw milk from which cheese was made. This led to a significant decrease of atherogenic index in cheeses produced from cows on pasture. Based on sensory analysis, cheese from animals kept on pasture was more yellow and had a lower intensity of butter and smoked odors than did CS cheese. In addition, grazing induced a lower intensity of bitter and a higher intensity of spicy flavors compared with cheese from CS animals. In regard to texture, pasture feeding resulted in higher intensity of friability and graininess. All cheeses performed well in consumer tests; the panel found all samples more than acceptable for overall liking, and for liking according to appearance, taste/flavor, and texture. Overall liking of Caciocavallo cheese, as assessed by slope analysis, was affected primarily by taste/flavor (raw slope k = 0.88) and texture (k = 0.97), whereas appearance had a lesser effect (k = 0.72). The acidic and sensory profiles of cheese were well discriminated, with healthier cheeses produced by grazing cows. Therefore, wider use of pasture should be promoted to accentuate this favorable feature. Based on the specific nutritional and sensory characteristics of mountain Caciocavallo cheese, particularly that obtained from grazing animals, efforts should be made to indicate the quality of this cheese to the consumer and improve product recognition.     

Redox thermodynamics of the native and alkaline forms of eukaryotic and bacterial class I cytochromes c

The reduction potentials of beef heart cytochrome c and cytochromes c2 from Rhodopseudomonas palustris, Rhodobacter sphaeroides, and Rhodobacter capsulatus were measured through direct electrochemistry at a surface-modified gold electrode as a function of temperature in nonisothermal experiments carried out at neutral and alkaline pH values. The thermodynamic parameters for protein reduction (DeltaS degrees rc and DeltaH degrees rc) were determined for the native and alkaline conformers. Enthalpy and entropy terms underlying species-dependent differences in E degrees and pH- and temperature-induced E degrees changes for a given cytochrome were analyzed. The difference of about +0.1 V in E degrees between cytochromes c2 and the eukaryotic species can be separated into an enthalpic term (-DeltaDeltaH degrees rc/F) of +0.130 V and an entropic term (TDeltaDeltaS degrees rc/F) of -0.040 V. Hence, the higher potential of the bacterial species appears to be determined entirely by a greater enthalpic stabilization of the reduced state. Analogously, the much lower potential of the alkaline conformer(s) as compared to the native species is by far enthalpic in origin for both protein families, and is largely determined by the substitution of Met for Lys in axial heme ligation. Instead, the biphasic E degrees /temperature profile for the native cytochromes is due to a difference in reduction entropy between the conformers at low and high temperatures. Temperature-dependent 1H NMR experiments suggest that the temperature-induced transition also involves a change in orientation of the axial methionine ligand with respect to the heme plane.     

Mesoporous carbons as low temperature fuel cell platinum catalyst supports

Platinum catalysts supported on ordered mesoporous carbons (OMC) are described. The mesoporous carbon support, CMK3 type, was synthesised as an inverse replica of a SBA-15 silica template. The platinum catalysts (i.e. Pt 20 wt% and Pt 10 wt%, respectively), obtained through a conventional wet impregnation method, have been investigated to determine their structural characteristics and electrochemical behaviour. The electro-catalytic performance towards the oxygen reduction reaction (ORR) was compared to those of commercial Pt/C-Vulcan XTC72R (E-Tek) catalysts with the same Pt wt%, under the same experimental conditions. The two catalyst samples have allowed the effect of the variation of both the Pt to Nafion and Pt to the supporting carbon ratios to be studied. Electrochemical tests have been carried out in three different systems: a catalyst ink deposited on a glassy carbon rotating disk electrode (RDE), a gas diffusion electrode (GDE) in a three-electrode cell with H₂SO₄ as the electrolyte and a complete PEM single fuel cell. The first results indicate that the OMC performs slightly less well than commercial carbon supports, mainly in the complete fuel cell system. The data from the cell tests indicate a less effective distribution of Nafion on the OMC surface which, probably, decreases the platinum utilisation and the proton conductivity.     

Comparison of xeroradiography and photographic radiography in the study of breast pathology

The peculiar characteristics of xeroradiography make it respond fully to the requirements of the radiographic represenattion of the breast. All the anatomical components of the breast are virtually identical as far as atomic number and low density are concerned. Xeroradiography has proved to be particularly suitable for highlighting the little difference in contrast between the various anatomical components of the breast. Pictures show the quality differences between traditional photographic mammography and xeromammography. The latter differs by its high power of resolution at all contrast levels thus making for easier identification of details and clearer outline, and by its broader exposure latitude making it possible to focus on a wider range of tissues. Visualization of dense, compact, youthful breasts [so-called opaque breasts] is also more reliable. Density differences can be exploited more effectively in cases of concomittance of two or more pathological situations such as: association of two mastopathic pictures, the presence of a small benignant formation or of a heteroplasia within an intensely dysplasic region. Thanks to a more smaller than immediate greater than interpretation of the picture, xeromammography also provides clearer evidence of the radiographic signs typical of benign neoformations and those typical of malignant forms.     

Prospects and utilization of xeroradiography in the osteoarticular diagnosis and study of soft parts

Xeroradiography and its physical phenomena are briefly described and attention is drawn to its offer of marked contrast and hence greater perception of details than conventional radiography. A comparison is made between ordinary and xero pictures of the spine, mediastinum and lungs with regard to the definition and identification of individual parts. The literature dealing with results obtained in areas where xeroradiography is best employed (joints and accompanying soft parts) is reviewed and personal experience in this field, based on a nosographic criterion and specific diagnostic choice, is presented. Cases illustrated cover ligamentous microcalcifications, knee meniscus calcifications, shoulder periarticular calcifications, and partial fractures. A comparison is made between conventional and xero pictures of joint changes in rheumatoid and uraemic arthritis, and bone changes in osteomyelitis and specific forms of arthritis. Diagnosis in osteo-necrosis and prosthesis complications is also examined. The results are such as to encourage further use of the method in the gathering of a fuller series of selected cases.     

Behavior and milk production of buffalo cows as affected by housing system

To verify the effect of 2 housing systems (with and without a pool and an ample outdoor lot) on behavior and milk yield, 45 lactating buffalo cows were group-housed in a free stall open-sided barn with concrete floor where they received 10 m²/head as space allowance (group NP); 43 cows were group-housed in a similar barn, but had access to an outdoor yard (36 m²/head) and a concrete pool of 208 m² (group WP). Animals were subjected to 8 sessions of instantaneous scan sampling at approximately 10-d intervals. Behavioral variables were expressed as proportions of subjects observed in each category of posture and activity. In addition, rapid behaviors such as agonistic, social, and reproductive interactions, social licking, and self-grooming were recorded continuously. These variables were expressed as number of interactions per animal. At the end of each hour of observation, temperature and relative humidity were recorded. In WP the proportion of animals observed wallowing was 0.476 ± 0.034, whereas lower proportions were observed standing (0.389 ± 0.029) or lying (0.141 ± 0.021) outside the pool. In NP the proportions of animals observed standing and lying were 0.452 ± 0.042 and 0.548 ± 0.042, respectively. A significant relationship between mean temperatures recorded on observation days and proportion of animals in the pool was observed (r_s = 0.41). Fewer animals from group WP were observed idling compared with buffaloes from group NP (0.44 ± 0.024 vs. 0.509 ± 0.024, respectively), whereas more WP animals were involved in investigative activities than NP cows (0.099 ± 0.009 vs. 0.042 ± 0.009, respectively). A greater number of social interactions (sniffing and nuzzling) and social lickings were observed in group WP than in group NP (0.120 ± 0.010 vs. 0.067 ± 0.010, and 0.151 ± 0.018 vs. 0.090 ± 0.018, respectively). The WP buffalo cows had a greater milk yield than NP cows (11.73 ± 0.31 vs. 10.78 ± 0.28 kg/d, respectively), whereas no differences between groups were observed for protein (4.86 ± 0.04 vs. 4.80 ± 0.03% for WP and NP, respectively) and fat contents (8.49 ± 0.14 vs. 8.38 ± 0.13% for WP and NP, respectively). We conclude that the provision of a pool and an ample outdoor paddock can have beneficial effects on welfare and milk production of buffaloes.