Synthesis and numerical simulation of formamidinium-based perovskite solar cells: a predictable device performance at NIS-Egypt

Formamidinium lead triiodide (δ-FAPbI₃)-based perovskite solar cells showed remarkable potential as light harvesters for thin-film photovoltaics. Herein, the mechanochemical synthesis of δ-FAPbI₃, MAPbI₃, and mixed-cation FA_1-xMA_xPbI₃ with (x = 0.3, 0.5, and 0.7) perovskite materials were prepared as a novel green chemistry method for scaling up production. Crystallinity, phase identification, thermal stability, optoelectronic properties, and nanoscale composition are discussed. The results demonstrated that the prepared mixed-cation samples are enhanced in the visible absorption region and are consistent with previous works. The crystal structure of δ-FAPbI₃ was altered to a cubic structure due to the change in FA-cation. Moreover, the performance of [Formula: see text]-FA-based perovskites was investigated using the Solar Cell Capacitance Simulator (SCAPS-1D) software. The validity of the device simulation was confirmed by comparing it to real-world devices. The photovoltaic characteristics and impact of absorber thickness on device performance were explained. The [Formula: see text]-FA-based solar cell with a 50% MA-doped molar ratio shows a better performance with an efficiency of 26.22% compared to 8.43% for δ-FAPbI₃. The outcome results of this work confirm the beneficial effect of mixed cations on device operation and advance our knowledge of the numerical optimization of perovskite-based solar cells.

Molecular mechanisms and clonal lineages of colistin-resistant bacteria across the African continent: A scoping review

Colistin (also known as Polymyxin E), a polymyxin antibiotic discovered in the late 1940s, has recently reemerged as a last-line treatment option for multidrug-resistant infections. However, in recent years, colistin-resistant pathogenic bacteria have been increasingly reported worldwide. Accordingly, the presented review was undertaken to identify, integrate and synthesize current information regarding the detection and transmission of colistin-resistant bacteria across the African continent, in addition to elucidating their molecular mechanisms of resistance. PubMed, Google Scholar, and Science Direct were employed for study identification, screening and extraction. Overall, based on the developed literature review protocol and associated inclusion/exclusion criteria, 80 studies published between 2000 and 2021 were included comprising varying bacterial species and hosts. Numerous mechanisms of colistin resistance were reported, including chromosomal mutation(s) and transferable plasmid-mediated colistin resistance (encoded by mcr genes). Perhaps unexpectedly, mcr-variants have exhibited rapid emergence and spread across most African regions. The genetic variant mcr-1 is predominant in humans, animals, and the natural environment, and is primarily carried by IncHI2- type plasmid. The highest numbers of studies reporting the dissemination of colistin-resistant Gram-negative bacteria were conducted in the North African region.

New fabrication method for di-indium tri-sulfuric (In2S3) thin films

Di-indium tri-sulfuric (In₂S₃) thin films are fabricated with annealing indium thin films in a sulfur environment. The effect of both annealing temperature and pressure on the structure, morphology, Raman, and photoluminescence (PL) spectroscopy has been studied. The X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) of the prepared thin films showed different structural phases and morphology with varying annealing temperature and pressure. Energy dispersive X-ray (EDX) analysis confirmed the chemical composition and the atomic ratio of In/S for the In₂S₃ thin films. The optimum annealing conditions of In₂S₃ thin films are 550 °C and 100 Torr. The outcome results revealed a new good growth method for In₂S₃ thin films to be used for different applications.

Digestibility and rumen fermentation of a high forage diet pre-treated with a mixture of cellulase and xylanase enzymes

Forages play an important role in ruminant animal production worldwide. Unlocking the nutritional potential of poor-quality tropical forages with fibrolytic enzymes would improve forage digestibility and utilization. Using in vitro and in vivo methods this study investigated the effect of pre-treating Smutsfinger hay for 24 hours with a mixture of fibrolytic enzyme (100% cellulase; 75% cellulase: 25% xylanase; 50% cellulase: 50% xylanase; 25% cellulase: 75% xylanase; 100% xylanase and a control with no enzyme) on ruminal fermentation and digestibility of nutrients by sheep. For in vitro fermentation, dry matter, neutral detergent fibre (NDF) degradability and volatile fatty acids (VFA) were determined with standard procedures. The same treatments were used for an in vivo digestibility trial using Merino sheep in a 6 x 6 Latin square design. Feed intake and total tract digestibility were recorded. Rumen fluid samples were collected daily, preserved, and analysed for VFA. The addition of 100% cellulase enzyme to Smutsfinger hay in vitro increased (P <0.05) NDF degradability and gas production compared with the control and inclusion of 100% xylanase enzyme. Both 100% cellulase and xylanase enzymes significantly reduced in vitro end time fermentation pH. A 50:50 mixture of cellulase and xylanase plus enzyme in vivo, increased acetate, total VFA concentration, and higher NDF and ADF digestibility of the test feed compared with the control. Inclusion of a 50-75% mixture of cellulase and 50-25% xylanase enzymes treatment led to higher gas production and butyrate concentration, decreased ruminal pH and improved nutrient digestibility.

Use of essential oils in combination with fibrolytic enzymes to decrease in vitro ruminal methane production

Exogenous enzymes and essential oils (EOs) have both improved fibre digestion in ruminants, but the effect on ruminal fermentation and methane emission of combining these additives requires further evaluation. Various EOs were used in combination with an enzyme in an in vitro gas production system to measure organic matter digestibility and methane after 48 hours of incubation of Eragrostis curvula. The treatments consisted of T1) unaugmented control; T2) enzyme (cellulose-xylanase mixture, 1:1 w/w, 1.5 mL/g DM); T3) enzyme combined with Next Enhance® (cinnamaldehyde with diallyl disulfide and diallyl trisulfide, 43:3.85 w/wt); T4) enzyme and cinnamon oil; T5) enzyme and garlic oil; and T6) enzyme with cinnamon and garlic oil, 1:1 w/w). At 2, 4, 8, 12, 24, 36, and 48 hours of incubation, gas production was measured, and gas samples were analysed for methane concentration. The inclusion of additives affected cumulative gas production (P <0.05), but only slightly affected methane production (P =0.05) after 48 hours of incubation. The addition of enzymes increased both gas and methane production. T5 and T6 both reduced gas production compared with T2. Combining EOs with an enzyme reduced methane production compared with T2 after 48 hours of incubation. The additives tended to increase in vitro organic matter digestibility (P =0.09), although they showed a tendency towards reduced methane production per unit of organic matter digested (P =0.07). Further studies on these enzyme and EO combinations under different doses and substrates are required to validate their efficacy for ruminant production. Keywords: cinnamon oil, cinnamaldehyde, garlic oil, gas production, glucanase, in vitro digestibility, xylanase

Substitution of Leucaena hay for oil seed cake meal in total mixed rations for goats

This study investigated the effects of incorporating different protein sources (oil seed cakes versus Leucaena leucocephala hay) in a total mixed ration (TMR) on intake, digestibility, growth and carcass meat quality of Saanen goats. Sixteen Saanen male goats were allocated to TMR diets formulated with or without L. leucocephala hay at 25% of total dry matter (DM). The TMRs were formulated to be iso-nitrogenous, isocaloric and iso-neutral detergent fibre using two sources of crude protein from Leucaena hay or oilseed cake meal (OSCM), which is a blend of soybean, sunflower and cottonseed cake meal. Data were collected on nutrient digestibility and carcass quality parameters. The goats fed TMR with Leucaena had greater (P <0.05) dry matter intake compared with those fed the control diet. In contrast, the digestibility of DM, organic matter, crude protein, neutral detergent fibre, acid detergent fibre and feed conversion ratio did not differ (P >0.05) between the two dietary treatments. Between treatments, no differences were detected for slaughter bodyweight, empty bodyweight carcass weight, and dressing percentage. Nor were differences detected (P >0.05) for cooking loss percentage, back fat cover, and area of eye muscle (longissimus dorsi) and WarnerBratzler shear force between goats fed the two TMR diets. Replacing a portion of oilseed cake meal at 15% DM with Leucaena hay at 25% DM in TMR for Saanen goats would help rural farmers to reduce the cost of feeding.Keywords: body composition, digestibility, feed intake, growth, meat quality

Barriers to access to visceral leishmaniasis diagnosis and care among seasonal mobile workers in Western Tigray, Northern Ethiopia: A qualitative study

Background

Ethiopia bears a high burden of visceral leishmaniasis (VL). Early access to VL diagnosis and care improves clinical prognosis and reduces transmission from infected humans; however, significant obstacles exist. The approximate 250,000 seasonal mobile workers (MW) employed annually in northwestern Ethiopia may be particularly disadvantaged and at risk of VL acquisition and death. Our study aimed to assess barriers, and recommend interventions to increase access, to VL diagnosis and care among MWs.

Methodology/Principal findings

In 2017, 50 interviews and 11 focus group discussions were conducted with MWs, mobile residents, VL patients and caretakers, community leaders and healthcare workers in Kafta Humera District, Tigray. Participants reported high vulnerability to VL among MWs and residents engaged in transitory work. Multiple visits to health facilities were consistently needed to access VL diagnosis. Inadequate healthcare worker training, diagnostic test kit unavailability at the primary healthcare level, lack of VL awareness, insufficient finances for care-seeking and prioritization of income-generating activities were significant barriers to diagnosis and care. Social (decision-making and financial) support strongly and positively influenced care-seeking; workers unable to receive salary advances, compensation for partial work, or peer assistance for contract completion were particularly disadvantaged. Participants recommended the government/stakeholders intervene to ensure: MWs access to bed-nets, food, shelter, water, and healthcare at farms or sick leave; decentralization of diagnostic tests to primary healthcare facilities; surplus medications/staff during the peak season; improved referral/feedback/reporting/training within the health system; free comprehensive healthcare for all VL-related services; and community health education.

Conclusions/Significance

Contrary to what health policy for VL dictates in this endemic setting, study participants reported very poor access to diagnosis and, consequently, significantly delayed access to treatment. Interventions tailored to the socio-economic and health needs of MWs (and other persons suffering from VL) are urgently needed to reduce health disparities and the VL burden.

Ethiopia bears a high burden of visceral leishmaniasis (VL)—a neglected tropical disease transmitted through the bite of a sand fly that disproportionately affects vulnerable populations. Without treatment, VL progresses, causing increasingly severe symptoms and ultimately death within two years, in most cases. Early access to VL diagnosis and care improves clinical prognosis and reduces transmission from infected humans; however, significant obstacles exist. To our knowledge, our study is the first in Ethiopia to use qualitative methods to assess barriers to VL diagnosis and care among seasonal mobile workers. Strikingly, we found that contrary to what health policy for VL dictates in this endemic setting, study participants reported very poor access to diagnosis and, consequently, significantly delayed access to treatment. Our findings have important public health and policy implications. Specifically, our results offer strategies that may increase access to VL diagnosis and care, allowing for earlier treatment and better prognoses for VL patients, and reducing the potential health disparities and the overall burden of VL.

Feasibility of early physical therapy for dizziness after a sports-related concussion: A randomized clinical trial

The purpose of this study was to (a) assess the feasibility of recruitment/retention of participants, protocol/resource management, and participant safety, and (b) estimate the size of the effect between the experimental and control groups. This was a feasibility study conducted as a prospective pilot double-blind randomized clinical trial. Subjects aged 10-23 years old with acute concussion and dizziness were enrolled from sports medicine centers. Forty-one participants were randomized into treatment and were seen for physical therapy beginning at 10 days post-concussion. Subjects in the experimental group received individually tailored, pragmatically delivered progressive interventions. Subjects in the control received prescriptive sham to minimally progressive interventions. The two primary outcomes were medical clearance for return-to-play and symptomatic recovery. The median number of days to medical clearance for the experimental group was 15.5 and for the control was 26. The median number of days to symptomatic recovery was 13.5 for the experimental group and was 17 for the control. According to Cox proportional hazards regression for time to medical release for return-to-play, the experimental group demonstrated a hazard ratio of 2.91 (95% CI: 1.01, 8.43) compared to the control. For time-to-symptomatic recovery, those in the experimental group demonstrated a hazard ratio of 1.99 (95% CI: 0.95, 4.15) compared to the control. The results indicate that it is feasible and safe to complete this type of intervention study. The results provide strong support for the allocation of resources to conduct well-powered randomized clinical trials of this intervention.

Genetic characterization and antimicrobial resistance of Staphylococcus aureus isolated from bovine milk in Tunisia

Staphylococcus aureus is a major agent of bovine mastitis in dairy herds, causing economic losses in dairy industry worldwide. In addition, milk and milk-products contaminated by Staph. aureus can cause harmful human diseases. The aim of this study was to characterize Staph. aureus strains isolated from dairy farms in Tunisia. Bulk tank milk (n = 32) and individual cow milk (n = 130) samples were collected during the period of 2013-2014. Forty-three Staph. aureus isolates were recovered and typed by spa typing, 16S-23S rRNA intergenic spacer (RS-PCR) and multiplex PCRs for 22 virulence genes. Antimicrobial resistance was also investigated with a disc diffusion test. A selected subsample of 22 strains was additionally genotyped by multilocus sequence typing. Seventeen spa types were recovered, and t2421 (n = 10), t521 (n = 6) and t2112 (n = 5) were the most common. Fourteen different RS-PCR genotypes grouped into 11 clusters were detected in our study, with predominance of the R^VI genotype (n = 24). Eight sequence types were identified and Clonal Complex 97, corresponding to RS-PCR cluster R, was the most common (n = 10), followed by CC1 (n = 4), CC15 (n = 3) and other four accounting for one or two strains. Different combinations of virulence genes were reported, and enterotoxin genes were present in few strains (seh, n = 4; sea, n = 2; sea and seh, n = 2; sec and sel, n = 2). The majority of strains were resistant only to penicillin; only one strain was found to be multiresistant and no methicillin-resistant Staph. aureus was demonstrated. Our study reported the isolation of CC97 from bovine milk in Tunisia for the first time and confirmed the relevance of this lineage in intramammary infection in cows.

SIGNIFICANCE AND IMPACT OF THE STUDY

This paper describes the characteristics of Staphylococcus aureus isolated from bulk tank and individual cow milk in Tunisia. All strains were genotyped by spa typing and RS-PCR, a method based on the amplification of the 16S-23S rRNA intergenic spacer region, and multiplex PCRs for 22 virulence genes. A selected subsample of strains was also genotyped by multilocus sequence typing. All strains were tested for antimicrobial resistance. Our study evidences a predominance of strains belonging to Clonal Complex 97. Methicillin-resistant strains were not detected, and overall low level of antimicrobial resistance was reported.

Predicting the digestible energy of corn determined with growing swine from nutrient composition and cross-species measurements

The DE values of corn grain for pigs will differ among corn sources. More accurate prediction of DE may improve diet formulation and reduce diet cost. Corn grain sources ( = 83) were assayed with growing swine (20 kg) in DE experiments with total collection of feces, with 3-wk-old broiler chick in nitrogen-corrected apparent ME (AME) trials and with cecectomized adult roosters in nitrogen-corrected true ME (TME) studies. Additional AME data for the corn grain source set was generated based on an existing near-infrared transmittance prediction model (near-infrared transmittance-predicted AME [NIT-AME]). Corn source nutrient composition was determined by wet chemistry methods. These data were then used to 1) test the accuracy of predicting swine DE of individual corn sources based on available literature equations and nutrient composition and 2) develop models for predicting DE of sources from nutrient composition and the cross-species information gathered above (AME, NIT-AME, and TME). The overall measured DE, AME, NIT-AME, and TME values were 4,105 ± 11, 4,006 ± 10, 4,004 ± 10, and 4,086 ± 12 kcal/kg DM, respectively. Prediction models were developed using 80% of the corn grain sources; the remaining 20% was reserved for validation of the developed prediction equation. Literature equations based on nutrient composition proved imprecise for predicting corn DE; the root mean square error of prediction ranged from 105 to 331 kcal/kg, an equivalent of 2.6 to 8.8% error. Yet among the corn composition traits, 4-variable models developed in the current study provided adequate prediction of DE (model ranging from 0.76 to 0.79 and root mean square error [RMSE] of 50 kcal/kg). When prediction equations were tested using the validation set, these models had a 1 to 1.2% error of prediction. Simple linear equations from AME, NIT-AME, or TME provided an accurate prediction of DE for individual sources ( ranged from 0.65 to 0.73 and RMSE ranged from 50 to 61 kcal/kg). Percentage error of prediction based on the validation data set was greater (1.4%) for the TME model than for the NIT-AME or AME models (1 and 1.2%, respectively), indicating that swine DE values could be accurately predicted by using AME or NIT-AME. In conclusion, regression equations developed from broiler measurements or from analyzed nutrient composition proved adequate to reliably predict the DE of commercially available corn hybrids for growing pigs.

IFT88 influences chondrocyte actin organization and biomechanics

OBJECTIVES

Primary cilia are microtubule based organelles which control a variety of signalling pathways important in cartilage development, health and disease. This study examines the role of the intraflagellar transport (IFT) protein, IFT88, in regulating fundamental actin organisation and mechanics in articular chondrocytes.

METHODS

The study used an established chondrocyte cell line with and without hypomorphic mutation of IFT88 (IFT88(orpk)). Confocal microscopy was used to quantify F-actin and myosin IIB organisation. Viscoelastic cell and actin cortex mechanics were determined using micropipette aspiration with actin dynamics visualised in live cells transfected with LifeACT-GFP.

RESULTS

IFT88(orpk) cells exhibited a significant increase in acto-myosin stress fibre organisation relative to wild-type (WT) cells in monolayer and an altered response to cytochalasin D. Rounded IFT88(orpk) cells cultured in suspension exhibited reduced cortical actin expression with reduced cellular equilibrium modulus. Micropipette aspiration resulted in reduced membrane bleb formation in IFT88(orpk) cells. Following membrane blebbing, IFT88(orpk) cells exhibited slower reformation of the actin cortex. IFT88(orpk) cells showed increased actin deformability and reduced cortical tension confirming that IFT regulates actin cortex mechanics. The reduced cortical tension is also consistent with the reduced bleb formation.

CONCLUSIONS

This study demonstrates for the first time that the ciliary protein IFT88 regulates fundamental actin organisation and the stiffness of the actin cortex leading to alterations in cell deformation, mechanical properties and blebbing in an IFT88 chondrocyte cell line. This adds to the growing understanding of the role of primary cilia and IFT in regulating cartilage biology.

Effect of Tannin and Species Variation on In vitro Digestibility, Gas, and Methane Production of Tropical Browse Plants

Nineteen tanniferous browse plants were collected from South Africa to investigate their digestibility, gas production (GP) characteristics and methane production. Fresh samples were collected, dried in forced oven, and ground and analyzed for nutrient composition. In vitro GP and in vitro organic matter digestibility (IVOMD) were determined using rumen fluid collected, strained and anaerobically prepared. A semi- automated system was used to measure GP by incubating the sample in a shaking incubator at 39°C. There was significant (p<0.05) variation in chemical composition of studied browses. Crude protein (CP) content of the species ranged from 86.9 to 305.0 g/kg dry matter (DM). The neutral detergent fiber (NDF) ranged from 292.8 to 517.5 g/kg DM while acid detergent fiber (ADF) ranged from 273.3 to 495.1 g/kg DM. The ash, ether extract, non-fibrous carbohydrate, neutral detergent insoluble nitrogen, and acid detergent insoluble nitrogen and CP were negatively correlated with methane production. Methane production was positively correlated with NDF, ADF, cellulose and hemi-cellulose. Tannin decreased GP, IVOMD, total volatile fatty acid and methane production. The observed low methanogenic potential and substantial ammonia generation of some of the browses might be potentially useful as rumen manipulating agents. However, a systematic evaluation is needed to determine optimum levels of supplementation in a mixed diet in order to attain a maximal depressing effect on enteric CH4 production with a minimal detrimental effect on rumen fermentation of poor quality roughage based diet.

Nutritive Value of Grasses in Semi-arid Rangelands of Ethiopia: Local Experience Based Herbage Preference Evaluation versus Laboratory Analysis

We examined the nutritive value of common grass species in the semi-arid rangelands of Borana in southern Ethiopia using local experience based herbage preference (LEBHP) perception and laboratory techniques. Local pastoralists in the study area were asked to identify common grass species and rank them according to the species' preferences and palatability to cattle. The pastoralists listed a total of 15 common grass species which were then sampled during the main rain and cold dry seasons and analyzed for crude protein (CP), Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF) and ash content to verify pastoralists' claim regarding the quality of individual species. The relative feed value (RFV) and dry matter digestibility (DMD) were also calculated using NDF and ADF contents. Spearman's rank correlation was used to examine possible relationships between laboratory results and pastoralists' experience on grass quality. Cenchrus ciliaris, Chrysopogon aucheri, Digitaria milanjiana, Eragrostis papposa and Panicum maximum were the top five species based on LEBHP perception. There were indications of inconsistency in terms of LEBHP perception among the different pastoral communities. The chemical composition of all grass species showed significant (p<0.05) variation between sites, seasons and species. The results showed that the CP values for the Borana rangelands were in the range of 8.7% in the main rain season to 5.1% for the cold dry season. The fiber constituents were relatively low in the main rain season compared to the cold dry season. Overall, Digitaria milanjiana had the highest CP (16.5%) content, while the least was recorded with Heteropogon contortus (10.8) and Aristida adoensis (9.8%) during the main rain season. It seems that the spatial variability of landscapes within the wider geographical regions, soil properties and texture, and land-use patterns probably contributed to site differences in species quality. Generally, the RFV of individual grass species was significantly (p<0.05) varied between and within sites. The ranking of species by pastoralists according to their preferences by cattle was highly correlated with the chemical composition of laboratory results of individual grass species with 'r' values for CP (0.94), ash (0.95), NDF (-0.98), ADF (-0.93) and ADL (-0.93). We suggest the complimentary use of LEBHP and laboratory techniques in evaluating the nutritive quality of rangeland forage species for sustainable animal production.

Risky driving behaviors for road traffic accident among drivers in Mekele city, Northern Ethiopia

BACKGROUND

Due to its perception as a disease of development, road traffic accident and related injuries tend to be under recognized as a major health problem in developing countries. However, majority of the world's fatalities on the roads occur in low income and middle income countries. Since the main cause of road traffic accident is attributed to human risky behaviors, it is important to identify significant factors for risky behaviors of drivers.

METHODS

A quantitative cross-sectional study with a sample size of 350 drivers was conducted in April 2011. The study was conducted among Taxi, Bajaj (three tire vehicles) and private owned car drivers. After proportion to size allocation for Taxi (75), Baja (103) and private owned car (172) drivers, we used systematic random sampling method to identify illegible study subjects. Data was collected with face to face interview using a pretested questioner. Univariate, bivariate and multivariate analysis was done using SPSS version 16.

RESULTS

The mean age of the respondents was 28.7 (SD 9.9). Majority were 339 (96.9%) males. Significant number of the study subjects 233 (66.6%) had risky driving behaviors. More than a quarter 100 (28.6%) had less knowledge about basic traffic signs. Majority of drivers 181 (51.7%) had negative attitude towards risky driving behaviors. Significant percent of them 148 (42.3%) had a habit of using mobile phone while driving vehicle and 28 (9.7%) had experience of driving after drinking alcohol. All the Bajaj, 97(62.6%) house car and 58(37.4%) taxi unfasten their seat belt while driving. Majority 303 (86.6%) followed the recommended speed limit of driving. About 66 (18.9%) of them had experience of punishment or warning by traffic polices in the previous 1 year and 77 (22%) ever had car accident while driving.

CONCLUSIONS

Drivers of secondary education and with high average monthly income were more likely to have risky driving behavior. Having supportive attitude towards risky driving behaviors and not getting advice about risky driving from significant others increases the likelihood of developing risky driving behavior. Interventions targeted at developing negative attitude towards risky driving behaviors on drivers and significant others should be implemented to bring positive behavior change. The interventions need to be segmented with educational status and income.

A novel phenotype based on esterase electrophoretic polymorphism for the differentiation of Lactococcus lactis ssp. lactis and cremoris

AIMS

To evaluate the esterase phenotype in Lactococcus lactis strains isolated from traditional Tunisian dairy products.

METHODS AND RESULTS

A collection of 55 L. lactis strains isolated from traditional fermented milk products and three reference strains were identified at species and subspecies level using molecular methods targeted to the 16S rRNA gene and to the histidine operon. The genotypic data obtained allowed the identification of the strains as L. lactis ssp. lactis and L. lactis ssp. cremoris with the prevalence of the ssp. lactis. The phenotypic identification based on arginine hydrolysis, the growth at 40 degrees C and in presence of 4% NaCl showed several discrepancy with the identification data based on genotypic analysis. Additional experiments carried out evaluating the esterase electrophoretic patterns revealed four classes of esterases identified on the basis of their electrophoretic mobility and specific activity on alpha- and beta-naphthyl ester of acetate and propionate. Esterase profiles discriminated the strains in two main groups corresponding to the subspecies cremoris and lactis according to a DNA-based identification.

CONCLUSIONS

The evaluation of esterase activity represents a novel phenotype for the taxonomic discrimination of the L. lactis ssp. lactis and cremoris.

SIGNIFICANCE AND IMPACT OF THE STUDY

Besides the DNA-based techniques that allow the rapid and accurate species/subspecies identification, the electrophoretic esterase profiles of L. lactis strains represents: (i) a new phenotypic tool to understand the physiology and the ecology of this species; and (ii) a new test for the potential selection of flavour producing strains.

Partitioning variances of growth in ultrasound longissimus muscle area measures in Angus bulls and heifers

The objective of the study was to estimate variance components, heritability, and repeatability of ultrasound longissimus muscle area (ULMA) measures. Data included 4,653 serial ULMA measures from 882 purebred Angus bulls and heifers. Animals were born over a 4-yr period from 1998 to 2001. Each year, bulls and heifers were ultrasonically scanned four to eight times, with a 4- to 6-wk interval between scans. Initially, data were subdivided by scan session across years and were analyzed in a multitrait model (MTM). Data pooled across years and scan session were then analyzed using random regression models (RRM) to estimate trends in genetic parameter estimates. Additive direct genetic variance increased with advancing scan session ranging from 8.67 cm4 at the first scan (mean age = 35 wk) to a maximum of 19.48 cm4 at the sixth scan (mean age = 56 wk). Heritability of ULMA increased from 0.35 at first scan to a maximum of 0.48 at the fourth scan (mean age = 50 wk). Additive direct genetic variance and heritability values at about 1 yr of age (fifth scan) were 18.24 cm4 and 0.45, respectively. Estimates from RRM also showed an increase in sigma(a)2 and h2 with age. Trends in sigma(pe)2 estimates, although tending to fluctuate, also increased with age. Additive direct genetic variance at 1 yr of age ranged from 15.8 cm4 to 17.0 cm4 for the different models. Heritability of yearling ULMA measures ranged from 0.40 to 0.42 and repeatabilities ranged from 0.80 to 0.84. For the range of ages used in the current study, both MTM and RRM showed close to maximum heritability values at around 1 yr of age. Therefore, phenotypic differences in yearling ULMA between Angus cattle are better indicators of genetic differences than earlier measurements. Angus breeders could, therefore, use ULMA measures made at around 1 yr of age to select next generation parents.

Microbial and copper adsorption by smectitic clay--an experimental study

The objective of this study was to quantify copper-, bacteria- and bacteriophage-binding capacities of natural clay with the aim of predicting the adsorption of heavy metals, human pathogenic bacteria and viruses by a clayey landfill liner. X-ray diffraction analysis of six natural clays showed that the dominant phase in all deposits consists of smectites together with illite, kaolin and, sometimes, palygorskite and sepiolite. The specific surface areas of different clay substrates were very high ranging from 293 to 351 m2 g(-1), and indicating a high proportion of phyllosilicates, consisting especially of smectites. The physico-chemical identification of separated smectites showed a high potential adsorbent character indicative of a large industrial use. The Kb12 smectite substrate chosen arbitrarily among six separated substrates, appeared as an excellent copper adsorbent. Copper was adsorbed to clay in a proportion ranging from 94.6 to 96.0% with an average of 95.1% and its adsorption occurred rapidly in less than 30 min. Organic contents of the clay substrate, evaluated as 17% of dry mass, may contribute and enhance copper adsorption. Different elution protocols using distilled water, 2 and/or 5% nitric acid revealed that while nitric acid resulted in the removal of more than 59% of the metal at the lower concentration and its complete depletion with a further elution at the higher concentration, distilled water alone was unable to remove more than 1% of adsorbed copper. This finding suggested that copper ions form high-energy bonds with layer-silicate surfaces. Interestingly, the use of a regenerated substrate as copper adsorbent subsequent to abundant washings of the used substrate consecutively, with 0.1 N HNO3 and distilled water, reduced copper adsorption by approximately 14%, suggesting a slight disturbance of clay initial structure. Batch adsorption experiments with phage T7 and raw clay Kb12 showed that the tested clay substrate appeared as a relatively moderate phage adsorbent since the quantity of adsorbed phage averaged 98.2 +/- 0.88% (2 log10 retention) as measured by infectivity for Escherichia coli ATCC 11303. As shown by two types of separating procedures, natural sedimentation and a low speed centrifugation, bacteriophage particles were bound essentially to fine and not to relatively coarse particles of the clay suspension. The retention capacity of purified clay Kb12 appeared low, with average values lower than 60 and 50%, for Pseudomonas aeruginosa ATCC 15442 and Bacillus cereus ATCC 1135, respectively. A significant increase of retention, in the order of 30%, was found for both bacteria when the mixture clay-bacteria was incubated at laboratory temperature for 6 hours.

Estimation of genetic parameters for ultrasound-predicted percentage of intramuscular fat in Angus cattle using random regression models

The present study included 3,358 observations of 675 bulls and heifers from the Iowa State University beef cattle breeding project. Data were collected over a 3-yr period between 1998 and 2000. Each year, cattle were scanned four to six times for ultrasound-predicted percentage of intramuscular fat (UPFAT) and other ultrasound traits, starting at a minimum age of 28 wk. The objective of the current study was to estimate variance components, heritability, and repeatability of UPFAT in young bulls and heifers. Data were subjected to random-regression animal models that included fixed effects of contemporary group, fixed Legendre polynomial of age at measurement, and random regression coefficients on Legendre polynomial of age at measurement for animals' direct genetic and direct permanent environmental effects. Phenotypic and genetic models involving different levels of polynomial fit for the animal component were considered. A model fitting a linear effect of Legendre polynomial of age at a measurement for animal direct genetic and direct permanent environmental effects and a homogeneous error variance described the present data adequately. Heritability of UPFAT ranged from 0.32 at 28 wk of age to a maximum of 0.53 at 63 wk. Repeatability of UPFAT increased from a minimum of 0.60 at ages of 28 to 39 wk to a maximum of 0.80 at ages 61 to 63 wk. Heritability and repeatability of yearling UPFAT were 0.50 and 0.71, respectively. With the exception of minor differences at earlier ages, fitting heterogeneous error variances did not have an effect on genetic parameter estimates for most ages of measurement. The present results showed an optimal heritability and repeatability of UPFAT measures around 52 wk and through at least 63 wk of age. This suggested that differences in UPFAT measures during this period also are good measures of differences in marbling genetic potential of Angus cattle.

Microbial characterization during composting of municipal solid waste

This study investigates the prevailing physico-chemical conditions and microbial community; mesophilic bacteria, yeasts and filamentous fungi, bacterial spores, Salmonella and Shigella as well as faecal indicator bacteria: total coliforms, faecal coliforms and faecal Streptococci, present in a compost of municipal solid waste. Investigations were conducted in a semi-industrial pilot plant using a moderate aeration during the composting process. Our results showed that: (i) auto-sterilization induced by relatively high temperatures (60-55 degrees C) caused a significant change in bacterial communities. For instance, Escherichia coli and faecal Streptococci populations decreased, respectively, from 2 x 10(7) to 3.1 x 10(3) and 10(7) to 1.5 x 10(3) cells/g waste dry weight (WDW); yeasts and filamentous fungi decreased from 4.5 x 10(6) to 2.6 x 10(3) cells/g WDW and mesophilic bacteria were reduced from 5.8 x 10(9) to 1.8 x 10(7) bacteria/g WDW. On the other hand, the number of bacterial spores increased at the beginning of the composting process, but after the third week their number decreased notably; (ii) Salmonella disappeared completely from compost by the 25th day as soon as the temperature reached 60 degrees C; and (iii) the bacterial population increased gradually during the cooling phase. While Staphylococci seemed to be the dominant bacteria during the mesophilic phase and at the beginning of the thermophilic phase, bacilli predominated during the remainder of the composting cycle. The appearance of gram-negative rods (opportunistic pathogens) during the cooling phase may represent a serious risk for the sanitary quality of the finished product intended for agronomic reuse. Compost sonication for about 3 min induced the inactivation of delicate bacteria, in particular gram-negatives. By contrast, gram-positive bacteria, especially micrococcus, spores of bacilli, and fungal propagules survived, and reached high concentrations in the compost.

Impact of Heavy Metals on the Selective Phenotypical Markers of Pseudomonas aeruginosa

The aim of this study was to characterize the impact of heavy metals on phenotypical markers of Pseudomonas aeruginosa. Twenty-two isolates of P. aeruginosa, either clinical (20) or secondary treated wastewater (2), were used to inoculate micro-ecosystems of sterile distilled water or secondary waste effluent in the presence of subminimal inhibitory concentrations of a variety of heavy metals commonly encountered in the aquatic naturally habitat (Ca2+, Co2+, Cr3+, Cu2+, Hg2+, Ni2+, Zn2+). Micro-ecosystems were exposed to visible light at laboratory temperature and individual strains were reisolated after a 1-, 3-, or 6-month period. The re-isolates (129) were characterized using hierarchical classification analysis in order to define affinities among variants of P. aeruginosa. Subsequently, discriminant analysis was used to detect eventual relationships among the different phenotypical markers studied. Results of the hierarchical classification, based on qualitative or quantitative approaches, showed clearly that incubation of P. aeruginosa in the presence of heavy metals altered the studied phenotypical markers, namely serotype, phage type, MIC of metals, and pyocin type. Discriminant analysis showed that the studied phenotypical markers could be classified into four clusters: C1 (L1 and L2 phage types, Hg tolerance and/or resistance, S2 serotype), C2 (P2 pyocin type, Cd tolerance and/or resistance, S1 serotype), C3 (Co and Cr tolerance and/or resistance) and C4 (P1 pyocin type, Ni, Zn, and Cu tolerance and/or resistance).

Thuricin 7: a novel bacteriocin produced by Bacillus thuringiensis BMG1.7, a new strain isolated from soil

AIMS

Detection and identification of new antagonistic activities towards Bacillus cereus and relatives.

METHODS AND RESULTS

Twenty Bacillus thuringiensis strains were screened for their capacity to express bacteriocin-like agents. Strain BMG1.7, isolated from soil, showed an antagonistic activity called thuricin 7. Thuricin 7 was active against several species of the genus Bacillus, including three of the four known B. thuringiensis/B. cereus bacteriocin producers, as well as against Streptococcus pyogenes and Listeria monocytogenes strains. Antimicrobial activity was lost after treatment with proteinase K. The active protein had an apparent molecular weight of 11.6 kDa, and was secreted at the end of the exponential growth phase. Thuricin 7 retained 55% of the activity after incubation at 98 degrees C for 30 min. The mode of action of thuricin 7 was shown to be bactericidal and bacteriolytic.

CONCLUSION

Thuricin 7 is a novel bacteriocin produced by a newly isolated Bacillus thuringiensis strain BMG1.7.

SIGNIFICANCE AND IMPACT OF THE STUDY

The characteristics of thuricin 7 indicate that it is a new bacteriocin which may have interesting biotechnological applications due to its relatively large activity spectrum.

Thuricin 7: a novel bacteriocin produced by Bacillus thuringiensis BMG1.7, a new strain isolated from soil

AIMS

Detection and identification of new antagonistic activities towards Bacillus cereus and relatives.

METHODS AND RESULTS

Twenty Bacillus thuringiensis strains were screened for their capacity to express bacteriocin-like agents. Strain BMG1.7, isolated from soil, showed an antagonistic activity called thuricin 7. Thuricin 7 was active against several species of the genus Bacillus, including three of the four known B. thuringiensis/B. cereus bacteriocin producers, as well as against Streptococcus pyogenes and Listeria monocytogenes strains. Antimicrobial activity was lost after treatment with proteinase K. The active protein had an apparent molecular weight of 11.6 kDa, and was secreted at the end of the exponential growth phase. Thuricin 7 retained 55% of the activity after incubation at 98 degrees C for 30 min. The mode of action of thuricin 7 was shown to be bactericidal and bacteriolytic.

CONCLUSION

Thuricin 7 is a novel bacteriocin produced by a newly isolated Bacillus thuringiensis strain BMG1.7.

SIGNIFICANCE AND IMPACT OF THE STUDY

The characteristics of thuricin 7 indicate that it is a new bacteriocin which may have interesting biotechnological applications due to its relatively large activity spectrum.

Predicting percentage of intramuscular fat using two types of real-time ultrasound equipment

In the present study, 500 steers were used to develop models for predicting the percentage of intramuscular fat (PIMF) in live beef cattle. Before slaughter, steers were scanned across the 11th and 13th ribs using Aloka 500V (AL-500) and Classic Scanner 200 (CS-200) machines. Four to five images were collected per individual steer using each machine. After slaughter, a cross-sectional slice of the longissimus muscle from the 12th rib facing was used for chemical extraction to determine actual carcass percentage of intramuscular fat (CPIMF). Texture analysis software was used by two interpreters to select a region for determination of image parameters, which included Fourier, gradient, histogram, and co-occurrence parameters. Four prediction models were developed separately for each of AL-500 and CS-200 based on images captured by the respective machines. These included models developed without transformation of CPIMF (Model I), models based on logarithmic transformation of CPIMF (Model II), ridge regression procedure (Model III), and principal component regression procedure (Model IV). Model R2 and root mean square error of AL-500 Models I, II, III, and IV were 0.72, 0.84%; 0.72, 0.85%; 0.69, 0.91%; and 0.71, 0.86%; respectively. The corresponding R2 and root mean square error values of CS-200 Models I, II, III, and IV were 0.68, 0.87%; 0.70, 0.85%; 0.64, 0.94%; and 0.65, 0.91%; respectively. Initially, AL-500 and CS-200 prediction models were validated separately on an independent data set from 71 feedlot steers. The overall mean bias, standard error of prediction, and rank correlation coefficient across the four AL-500 models were 0.42%, 0.84%, and 0.88, respectively. For the four CS-200 models, the corresponding overall mean values were 0.67%, 0.81%, and 0.91, respectively. In a second validation test, only Model II of AL-500 and CS-200 was evaluated separately based on data from 24 feedlot steers. The overall mean bias, absolute difference, and standard error of prediction of AL-500 Model II were 0.71, 0.92, and 0.98%. For CS-200 Model II, the corresponding values were 0.59, 0.97, and 1.03%. Both AL-500 and CS-200 equipment can be used to accurately predict PIMF in live cattle. Further improvement in the accuracy of prediction equations could be achieved through increasing the development data set and the variation in PIMF of cattle used.

Repeatability of ultrasound-predicted percentage of intramuscular fat in feedlot cattle

We used data from 144 bulls, heifers, and steers to determine the repeatability of ultrasound-predicted percentage of intramuscular fat and to study the effect of repeated measurements on the standard error of prediction. Animals were scanned at an average age of 433 d by a certified technician. Individual bulls, heifers, and steers were scanned five to six times each with two Aloka 500-V machines, and the percentage of intramuscular fat was predicted from two regions of interest within an image. Variance components and repeatability values were computed for the overall data and by machine, region of interest, and sex. Animals were broadly divided into two groups based on mean ultrasound-predicted percentage of intramuscular fat. Variance components and repeatability values were then estimated within each group. The overall repeatability of ultrasound-predicted percentage of intramuscular fat was .63 +/- .03. Differences in the repeatability values between machines and between regions of interest were not different from zero (P > .05). Bulls showed a lower within-animal SD of .82% as compared to .97 and 1.02% for steers and heifers, respectively. However, steer ultrasound-predicted percentage of intramuscular fat measures were more repeatable (P < .05) than those of bulls and heifers. The difference in repeatability between bull and heifer measures was not important (P > .05). Animals with mean ultrasound-predicted percentage of intramuscular fat less than 4.79% showed less repeatable measures (P < .05) than those with means above 4.79%. The image variance contributed to nearly 70% of the total variance of observations within an animal. Standard error of animal mean measures showed a 50% reduction when the number of images per animal increased to four. Therefore, we concluded that increasing the number of images per animal plays a more significant role in reducing the standard error of prediction than taking multiple measurements within a single image.

Evaluation of carcass, live, and real-time ultrasound measures in feedlot cattle: I. Assessment of sex and breed effects

Carcass and live-animal measures from 1,029 cattle were collected at the Iowa State University Rhodes and McNay research farms over a 6-yr period. Data were from bull, heifer, and steer progeny of composite, Angus, and Simmental sires mated to three composite lines of dams. The objectives of this study were to estimate genetic parameters for carcass traits, to evaluate effects of sex and breed of sire on growth models (curves), and to suggest a strategy to adjust serially measured data to a constant age end point. Estimation of genetic parameters using a three-trait mixed model showed differences between bulls and steers in estimates of h2 and genetic correlations. Heritability for carcass weight, percentage of retail product, retail product weight, fat thickness, and longissimus muscle area from bull data were .43, .04, .46, .05, and .21, respectively. The corresponding values for steer data were in order of .32, .24, .40, .42, and .07, respectively. Analysis of serially measured fat thickness, longissimus muscle area, body weight, hip height, and ultrasound percentage of intramuscular fat using a repeated measures model showed a limitation in the use of growth models based on pooled data. In further evaluation of regression parameters using a linear mixed model analysis, sex and breed of sire showed an important (P < .05) effect on intercept and slope values. Regression of serially measured traits on age within animal showed a relatively larger R2 (62 to 98%) and a smaller root mean square error (RMSE, .09 to 8.85) as compared with R2 (0 to 58%) and RMSE (.31 to 67.9) values when the same model was used on pooled data. We concluded that regression parameters from a within-animal regression of a serially measured trait on age, averaged by sex and breed, are the best choice in describing growth and adjusting data to a constant age end point.

Evaluation of carcass, live, and real-time ultrasound measures in feedlot cattle: II. Effects of different age end points on the accuracy of predicting the percentage of retail product, retail product weight, and hot carcass weight

Data from 970 feedlot steers and bulls were used to evaluate effects of different age end points on the accuracy of prediction models for percentage of retail product, retail product weight, and hot carcass weight. Cattle were ultrasonically scanned three to five times for fat thickness, longissimus muscle area, and percentage of intramuscular fat. Live animal measures of body weight and hip height were also taken during some of the scan sessions. Before development of prediction equations, live and ultrasound data were adjusted to four age end points using individual animal regressions. Age end points represented mean age at slaughter (448 d), mean age at the second-to-last scan before slaughter (414 d), mean age at the third-to-last scan before slaughter (382 d), and an age end point of 365 d. Ultrasound and live animal measures accounted for a large proportion of the variation in the dependent variables regardless of the age end point considered. For all three traits, final models based on independent variables adjusted to earlier ages of 365 and 382 d showed better or at least similar model R2 and root mean square errors than those based on independent variables adjusted to a mean slaughter age of 448 d. Validation of the models using independent data from 282 steers resulted in a mean across-age rank correlation coefficient of .78, .88, and .83 between actual and predicted values of the percentage of retail product, hot carcass weight, and retail product weight, respectively. Mean across-age rank correlation of breeding values for the corresponding traits were .92, .89, and .82. The results of this study suggest that live and ultrasound traits measured as early as 365 d could be used to predict end product traits as accurately as similar measures made before slaughter at age 448 d.

Evaluation of ultrasound measurements of fat thickness and longissimus muscle area in feedlot cattle: Assessment of accuracy and repeatability

Data from two cattle feeding trials were used to estimate accuracy and repeatability of ultrasound measurements of 12–13th rib fat thickness and longissimus muscle area. In each trial, images from the last scan prior to slaughter were interpreted by two certified technicians. Each technician interpreted the image of each steer twice on two different days. Overall technician biases for ultrasound measurements of fat thickness and longissimus muscle area were −0.17 cm and 0.63 cm2, respectively. Mean bias in measurement of fat thickness by the two technicians was similar in amount and direction (−0.14 cm vs. −0.20 cm); however, bias in the measurement of longissimus muscle area by the two technicians took an opposite direction (−1.28 cm2 vs. 2.54 cm2). Repeatability of ultrasound-measured fat thickness was the same for both technicians (0.96 to 0.97). However, measurements of technician A showed a better repeatability (0.92) than technician B (0.79) for ultrasound-measured longissimus muscle area. Generally, except for minor differences, degree of experience did not show a consistent difference in the accuracy of ultrasound estimation of fat thickness and longissimus muscle area. Hence, it was concluded that technicians could easily be trained to make accurate predictions of fat thickness and longissimus muscle area. Key words: Beef cattle, carcass, ultrasound, repeatability, accuracy

[Isolation of salmonella in wastewaters and study of indicator bacteria survival in soils]

Detection of salmonella in wastewaters was done in semi-industrial pilot plant. In parallel, survival of indicator bacteria (feacal coliforms and feacal streptococci) in the soil was evaluated into a laboratory incubation device. Results revealed the isolation of 21 strains of salmonella in 7 campaigns of analysis on DCLS media, and 6 strains on lactose-green-brilliant and phenol red media in 2 campaigns. Salmonella were recovered in all the lines of wastewater treatment. The study led on the survival of coliforms and streptococci bacteria allowed the conclusion that feacal streptococci introduced by wastewaters were more qualified to survive in the soil than feacal coliforms. On the other hand, feacal coliforms appeared more sensitive to the biological factors of the soil than feacal streptococci. The ambient temperature of incubation situated between 12 and 24 degrees C seemed suitable for bacteria survival in the soils.

[Hygienic aspects of aerobic fermentation of urban waste in the Tunisian context]

The use of the aerobic fermentation (composting) as an alternative of the landfilling of the municipal solid wastes was studied in a pilot plant in the District of Tunis. The effectiveness of the composting, by the windrow turning technical, in producing sanitized compost was considered. Fecal coliforms, fecal streptococcis and E. coli were used as an indicator organism. In addition, the evolution of the process was monitored using sporogenous bacteria. Under the experimental conditions, approximately five logarithmic unit reduction of fecal indicators was noted after a 60 days composting.