Validation of the Reveal® 3-D for Gluten Assay for Detection of Gluten in Clean-in-Place Rinses and Stainless Steel Environmental Surfaces: AOAC Performance Tested MethodSM 122201

BACKGROUND

Reveal® 3-D for Gluten is an immunochromatographic assay for the qualitative detection of gluten in environmental samples. The test uses monoclonal antibodies reactive to prolamins in wheat.

OBJECTIVE

The objective of the study was to validate the Reveal 3-D test for detection of gluten in clean-in-place rinse and swabs from a stainless steel surface.

METHODS

Elements of the study included food selectivity and interference testing, matrix testing, an assay robustness study, and reagent stability/lot-to-lot consistency testing. Wheat flour was used as the spiking material for all matrixes.

RESULTS

In selectivity and interference testing, nine target matrixes all tested positive and 36 of 39 non-target matrixes tested negative. Almond flour, sesame flour, and cornstarch produced positive results as 100% commodities; reactivity can be eliminated with dilution or by testing without use of food extraction buffer, which is not a standard part of the environmental testing method. With a gluten spike at 9.3 mg/kg, chestnut flour, guar gum, and xanthan gum as 100% commodities inhibited the ability of the assay to detect gluten when tested without dilution. In quaternary ammonium clean-in-place rinse and swabs from stainless steel, 100% positive results were obtained at levels of 2.8 mg/kg and 4.7 µg/100 cm2, respectively. Results of independent laboratory testing of swabs from stainless steel supported those of internal trials. Robustness testing showed that introducing variations to three operating parameters simultaneously had no adverse effect on assay performance. In the reagent stability study, data supported kit expiration dating of 11 months.

CONCLUSIONS

Results of the current study show that the Reveal test is an accurate and reliable method for qualitative detection of gluten in select clean-in-place rinse and environmental samples.

HIGHLIGHTS

The Reveal test was able to detect gluten at levels of 2.8 ppm in clean-in-place rinse and 4.7 µg/100 cm2 in swabs from stainless steel.

Validation of the Soleris® NF-TVC Method for Detection of Aerobic, Mesophilic Microorganisms in Dried Cannabis Flower: AOAC Performance Tested MethodSM 071203

Background

Soleris® Non-Fermenting Total Viable Count (NF-TVC) is a growth-based, automated method for semiquantitative detection of aerobic, mesophilic microorganisms in foods and other consumer products such as nutraceuticals and cosmetics. The method was granted AOAC Performance Tested MethodSM status for select foods after successful completion of a validation study.

Objective

The objective of the current study was to validate the Soleris NF-TVC method for use with dried cannabis flower [>0.3% delta 9-tetrahydrocannabinol (THC)].

Methods

The validation consisted of a comparative matrix study in which naturally contaminated dried cannabis flower was tested with the Soleris NF-TVC method and with the AOAC Official Methods of AnalysisSM  966.23 dilution plating method. Multiple lots of dried cannabis flower were obtained, pre-screened for total aerobic, mesophilic viable count levels, and blended to produce test materials at four different levels of contamination ranging from 1.0 × 103 to 2.2 × 105 CFU/g. Each material was tested at three different Soleris detection threshold levels determined by the dilution used to inoculate the Soleris vials. Probability of detection analysis was performed to determine if differences in the number of positive results obtained with the two methods were significant.

Results

For all four dried cannabis flower materials, at all three Soleris test thresholds, there were no significant differences in performance comparing the Soleris and reference dilution plating methods as determined by probability of detection analysis at P < 0.05.

Conclusions

It is concluded that the Soleris NF-TVC method is an accurate and effective method for detection of aerobic, mesophilic microorganisms in dried cannabis flower.

Highlights

The Soleris NF-TVC method provides cannabis industry quality control personnel with an effective method for analysis of dried cannabis flower and produces results in 24–48 h.

Validation of the Soleris® Coliform Method for Detection of Coliform Bacteria in Dried Cannabis Flower: AOAC Performance Tested MethodSM 010302

Background

The Soleris® Coliform Vial is a growth-based, automated method for detection of coliform bacteria in foods and other consumer products such as nutraceuticals and cosmetics. The method was granted AOAC Performance Tested MethodSM certification for select foods after successful completion of a validation study.

Objective

The objective of the current study was to validate the Soleris coliform method for use with dried cannabis flower (>0.3% delta 9-tetrahydrocannabinol).

Methods

A comparative matrix study was performed in which naturally contaminated dried cannabis flower was tested with the Soleris coliform method and with the U.S. Food and Drug Administration Bacteriological Analytical Manual solid medium method. Multiple lots of dried cannabis flower were obtained, pre-screened for coliforms, and blended to produce test materials at four different contamination levels ranging from 4.5 to 1600 CFU/g. Each material was tested at three different Soleris detection threshold levels determined by the dilution used to inoculate the Soleris vials. Probability of detection analysis was performed to determine if differences in the number of positive results obtained with the two methods were significant.

Results

For all four dried cannabis flower materials, at all three Soleris test thresholds, there were no significant differences in the number of positive results obtained with the Soleris and cultural plating methods as determined by probability of detection analysis at P < 0.05.

Conclusion

The Soleris coliform test is an accurate method for detection of coliform bacteria in dried cannabis flower.

Highlights

The Soleris coliform method provides cannabis industry QC personnel with an effective method for analysis of dried cannabis flower and produces results in 18–24 h.

Validation of the Soleris®Enterobacteriaceae Method for Detection of Enterobacteriaceae in Dried Cannabis Flower: AOAC Performance Tested MethodSM 121901

Background

The Soleris®Enterobacteriaceae vial is a growth-based, automated method for detection of bacteria of the family Enterobacteriaceae in foods and other sample types including nutraceuticals and cosmetics. The Soleris method is used in a “dilute-to-specification” or threshold manner, in which a result is scored as positive or negative around a predetermined cutoff (in CFU/g) established by the dilution and volume of sample homogenate tested. The Soleris method was granted AOAC Performance Tested MethodSM (PTM) status for select foods after successful completion of a validation study (PTM 121901).

Objective

The objective of this study was to validate the method for the detection of Enterobacteriaceae in dried cannabis flower [>0.3% delta-9-tetrahydrocannabinol (THC)].

Methods

The matrix study included comparison of Soleris method presumptive results to confirmation from the Soleris vials, and comparison of the Soleris confirmed results to those of the ISO 21528-2:2017 colony count method. Test materials at four different levels of contamination ranging from 7.8 to 3500 CFU/g were tested at three dilutions, corresponding to test thresholds.

Results

Probability of detection analysis at P < 0.05 showed there were no significant differences between Soleris presumptive and confirmed results, and no significant differences between Soleris confirmed and ISO 21528-2:2017 results.

Conclusion

The results provided evidence that the Soleris Enterobacteriaceae test is an accurate method for detection of Enterobacteriaceae in dried cannabis flower.

Highlights

The Soleris Enterobacteriaceae method provides cannabis industry QC personnel with an effective method for analysis of dried cannabis flower and produces results in 20–24 h.

Emergency Response Validation of the Soleris® Direct Yeast and Mold Method for Detection of Yeast and Mold in Dried Cannabis Flower: AOAC Performance Tested MethodSM 051301

BACKGROUND

Soleris® Direct Yeast and Mold is a growth-based, automated method for detection of yeast and mold in select foods and other sample types including nutraceuticals and cosmetics. The Soleris method is used in a "dilute-to-specification" or threshold manner in which a result is scored as positive or negative around a predetermined cutoff (in CFU/g) established by the dilution and volume of sample homogenate tested.

OBJECTIVE

The objective of this study was to validate the method for testing of dried cannabis flower. The validation was conducted under the Emergency Response Validation program of the AOAC Research Institute.

METHODS

The study included inclusivity and exclusivity testing, in particular testing of yeast and mold species associated with cannabis, and a matrix study in which Soleris method presumptive results were compared to Soleris confirmed results using Dichloran Rose Bengal Chloramphenicol agar for confirmation. Samples at four different levels of natural yeast and mold contamination were tested at two test thresholds.

RESULTS

In inclusivity testing, all 63 yeast and mold strains tested produced positive results within the specified test duration of 72 h. In exclusivity testing, 36 of 37 strains tested produced no detection within 72 h. In matrix testing, there were no significant differences between Soleris presumptive and confirmed results for any contamination level or test threshold as determined by probability of detection analysis.

CONCLUSIONS AND HIGHLIGHTS

Results indicate that the Soleris method is an effective procedure for detection of yeast and mold in dried cannabis flower. Results are available within 72 h compared with the 5-7 days required for microbiological culture methods.

Validation of Modifications to the Soleris® E. coli Method for Detection and Threshold Determination of Escherichia coli in Select Foods: Level 3 Modification AOAC Performance Tested MethodSM 101101

BACKGROUND

Soleris® E. coli is an automated, growth-based method for detection and semi-quantitative determination of Escherichia coli in foods. The method can be used in dilute-to-specification (threshold) or presence/absence modes.

OBJECTIVE

The objective of the study was to validate four modifications to the method: 1) a change in the vial detection window plug composition from agar to agarose to improve plug consistency and robustness, 2) a change in pre-enrichment incubation time for presence/absence testing from 6 h to 18-24 h, 3) a change in vial incubation temperature from 44.5 °C to 43.5 °C, and 4) incorporation of a simple direct-from-vial confirmation test as an alternative to traditional procedures.

METHODS

Elements of the study included inclusivity/exclusivity testing, matrix testing in comparison to the ISO 7251:2005 reference method, reagent stability/lot-to-lot consistency testing, and an independent laboratory study.

RESULTS

In inclusivity testing, all 55 E. coli strains tested produced positive results. In exclusivity testing, 30 of 31 strains of other bacterial species produced negative results, the sole exception being a strain of Enterobacter cloacae. In internal and independent laboratory matrix testing of mozzarella cheese, condensed milk, pasteurized liquid egg, and frozen green beans, results showed no significant differences in performance of the Soleris and reference methods with two exceptions, one in which the Soleris method produced more positive results, and one in which the reference method produced more positive results.

CONCLUSIONS AND HIGHLIGHTS

Performance characteristics of the modified Soleris E. coli method are consistent with those of the original validated method, while offering improvements in ease of use and reagent robustness.

Coupling ecological wastewater treatment with the production of livestock feed and irrigation water provides net benefits to human health and the environment: A life cycle assessment

Ecologically designed wastewater treatment systems (ex., Eco-Machines™) utilize a diverse ecosystem to treat wastewater to the same extent as conventional treatment, but require less energy and chemical inputs. The environmental benefits of Eco-Machines™ can be theoretically maximized by incorporating hyperaccumulating aquatic plants (ex., duckweed) to facilitate nutrient recovery and conversion into protein-rich biomass, which can then be harvested for a range of agricultural and bioenergy applications. Although it has been established that ecological wastewater treatment systems are more cost- and energy-efficient than conventional wastewater treatment systems, a systematic life cycle assessment (LCA) of an Eco-Machine™ coupled with its beneficial by-products has not been conducted. In this study, a series of LCAs were performed on different operational scenarios for a 1000 gallon per day, pilot-scale Eco-Machine™ that, in addition to producing irrigation-quality water, also produces duckweed biomass for aquaculture. The analysis revealed that Eco-Machines™ located in warm climates, which do not require a greenhouse or supplemental heating, use approximately a third of the energy and produce half of the greenhouse gas emissions compared to conventional wastewater treatment systems in similar locations, while also providing benefits to human health, ecosystem quality, climate change, and resources. In addition, increasing the growth area for duckweed using vertical farming techniques improves the overall impact of the system. This study suggests that with proper management, ecological wastewater treatment systems that upcycle nutrients and water into beneficial products can provide a net benefit to human health and the environment.

Validation of the One Broth One Plate for Salmonella Method for Detection of Salmonella Spp. in Select Food and Environmental Samples: AOAC Performance Tested MethodSM 102002

Background

One Broth One Plate for Salmonella (OBOP Salmonella) is a rapid and simple method for detection of Salmonella spp. in food and environmental samples using traditional culture methodology. The method utilizes single-step enrichment followed by plating to a selective/differential, chromogenic agar.

Objective

The purpose of the validation study was to measure the effectiveness of the OBOP Salmonella method in comparison to reference culture procedures.

Method

Performance of the OBOP Salmonella method was compared to that of the U.S. Food and Drug Administration Bacteriological Analytical Manual Chapter 5 reference method for queso fresco, smoked salmon, cantaloupe, chocolate, black pepper, chili powder, dry pet food, and sponge samples from a stainless steel surface, or to that of the U.S. Department of Agriculture Microbiology Laboratory Guidebook Chapter 4.10 method for raw ground turkey, chicken carcass rinse, and pasteurized liquid egg. Inclusivity/exclusivity, robustness, and stability/lot-to-lot consistency testing was also performed.

Results

In the matrix study, there were no statistically significant differences in performance between the OBOP Salmonella and reference methods, as determined by probability of detection analysis (P < 0.05), for any of the matrixes examined. All 104 Salmonella spp. strains produced positive results in inclusivity testing, and all 33 non-salmonellae exclusivity strains tested negative with the OBOP Salmonella method.

Conclusions

Results of the validation study show that the OBOP Salmonella method is a reliable procedure for detection of Salmonella spp. in select matrixes. The method is simple to perform, requires no specialized equipment, and produces results in as little as 37 h.

Highlights

The OBOP Salmonella method was awarded AOAC PTM^SM (#102002) for detection of Salmonella in queso fresco, smoked salmon, cantaloupe, chocolate, black pepper, chili powder, dry pet food, sponge samples on a stainless steel surface, raw ground turkey, chicken carcass rinse, and pasteurized liquid egg. The method is also approved by MicroVal^® for a broad range of foods under certification number 2019LR88.

Duckweed protein supports the growth and organ development of mice: A feeding study comparison to conventional casein protein

As global population growth and meat consumption increases, sustainable alternatives to conventional protein-rich fodder crops for livestock are needed to reduce negative environmental impacts. Duckweed, a small floating aquatic plant, can generate 5 to 10 times higher protein yields than conventional land-grown crops. Although some in vivo feeding trials with duckweed have been conducted, those measuring animal weight are limited, and those examining organ development are nonexistent. To secure broad acceptance of new protein sources, such controlled studies are critical. This study measured the food intake, growth, and final organ and adipose tissue mass of male CF-1 mice fed a semi-purified diet containing casein or diets in which 10% or 25% of the casein was replaced with duckweed protein (DWP). Proximate analysis showed that the DWP preparation used contained 39.9% protein (w/w), and contained all of the essential amino acids with Met as the limiting amino acid. The average growth rates were not significantly different among the treatment groups: 0.21 g/day; 0.24 g/day; and 0.25 g/day for the control, 10%, and 25% DWP protein diets, respectively. The daily food intake of both DWP diets was 6.5% to 8.0% higher than the control diet, but feeding efficiency did not differ among diets. The relative weight of the liver, spleen, kidneys, heart, and epidydimal fat, and colon length were not significantly different between treatment groups. The results from this study show that replacement of up to 25% dietary casein with DWP has no adverse effects on the growth rate and final organ and adipose tissue weights of laboratory mice. PRACTICAL APPLICATION: Duckweed can produce 5 to 10 times more protein per area than land-grown crops such as soybean. In this study, up to a 25% replacement of casein with duckweed protein had no observable effect on the growth or organ development of laboratory mice. Thus, duckweed has the potential to be used as a protein supplement for livestock, poultry, and fish, thereby decreasing environmental impacts from land-grown crops used for animal feed.

Validation of the Reveal® 3-D for Peanut Lateral Flow Test: AOAC Performance Tested MethodSM 111901

Background

Reveal^® 3-D for Peanut is an immunochromatographic, lateral flow test for qualitative detection of peanut residue in food manufacturing and food preparation settings. The test can detect low ppm levels of peanut in clean-in-place (CIP) rinses and in swabs from environmental surfaces and can serve as a tool in managing allergen risk.

Objective

The objective of the study was to validate the lateral flow method for detection of peanut in CIP rinses, specifically water, peroxyacetic acid/hydrogen peroxide, and quaternary ammonium compound rinses, and in swabs taken from stainless steel and plastic surfaces.

Methods

CIP rinses spiked with low levels of peanut were tested, as were surfaces inoculated with peanut. Specificity and assay interference were assessed in testing of food commodities with and without added peanut. Assay robustness and test kit stability and consistency testing were also performed.

Results

Results demonstrated that the lateral flow test can detect peanut in CIP rinses in the range of 2–4 ppm and in environmental surface swabs in the range of 3–4 µg/100 cm². Results of specificity testing with 29 common food items showed lack of cross-reactivity, and potential assay interference only from walnut. Data from stability trials supports expiration dating for the kit of up to 23 months post-manufacture.

Conclusions and Highlights

The lateral flow test is a sensitive, specific, and rapid method for detection of low levels of peanut residue in CIP rinses and environmental samples and can be an important component in a comprehensive allergen risk management program.

Soleris®Enterobacteriaceae for the Detection of Enterobacteriaceae in Select Foods: AOAC Performance Tested MethodSM 121901

Background

Soleris^®Enterobacteriaceae is a growth-based, automated method for detection of Enterobacteriaceae in food.

Objective

A study was conducted to validate the Soleris method for detection of Enterobacteriaceae in select foods (pasteurized milk, yogurt, mozzarella cheese, ice cream, dried milk, pasteurized liquid egg, frozen cooked chicken, deli ham, lettuce, and dry dog food) at a threshold of ≥ 10 CFU/g of product.

Methods

Inclusivity and exclusivity of the Soleris method were assessed by testing 55 and 38 target and non-target bacterial strains, respectively. Matrix testing was performed with one naturally contaminated and nine inoculated foods. Efficacy of the Soleris method was compared to that of the ISO 21528-2:2017 direct plating reference method using probability of detection analysis. Independent laboratory testing was conducted to verify method performance in two matrixes (yogurt and deli ham). Method robustness, stability, and lot-to-lot consistency of the Soleris reagents were also assessed.

Results

Inclusivity of the Soleris test was 91% and exclusivity was 100%. In matrix testing, there were no significant differences in the number of positive results obtained with the Soleris and reference methods for any of the matrixes examined. Overall, of 370 test portions, there were 176 positive results by the Soleris method and 177 positive results by the reference procedure.

Conclusions

Soleris Enterobacteriaceae is an effective method for detection of Enterobacteriaceae in the foods evaluated, with performance equivalent to that of the ISO 21528-2:2017 reference method.

Highlights

The Soleris method offers the advantages of labor savings and results within 18 h.

Elastocapillary adhesion of a soft cap on a rigid sphere

We study the capillary adhesion of a spherical elastic cap on a rigid sphere of a different radius. Caps of small area accommodate the combination of flexural and in-plane strains induced by the mismatch in curvature, and fully adhere to the sphere. Conversely, wider caps delaminate and exhibit only partial contact. We determine the maximum size of the cap enabling full adhesion and describe its dependence on experimental parameters through a balance of stretching and adhesion energies. Beyond the maximum size, complex adhesion patterns such as blisters, bubbles or star shapes are observed. We rationalize these different states in configuration diagrams where stretching, bending and adhesion energies are compared through two dimensionless parameters.

Matrix Extension Study: Listeria Right Now™ Test for Detection of Listeria spp. from Selected Environmental Surfaces Without Enrichment: AOAC Performance Tested MethodSM 081802

BACKGROUND

Listeria Right Now™ is a novel, enrichment-free test for the detection of Listeria spp. in swab samples taken from environmental surfaces. Results are available in less than 1 h. In a previous Performance Tested MethodSM (PTM) study, the test was validated for swab samples from stainless-steel and sealed concrete surfaces.

OBJECTIVE

A PTM matrix extension study was conducted to validate the method for the detection of Listeria spp. in swab samples from ceramic tile, plastic, and rubber surfaces.

METHODS

Performance of the Listeria Right Now method was compared to that of the U.S. Food and Drug Administration Bacteriological Analytical Manual reference culture procedure for the detection of Listeria spp. in swab samples taken from inoculated ceramic tile, plastic, and rubber surfaces. Data were analyzed using a probability of detection model.

RESULTS

There were no significant differences in performance between the Listeria Right Now and reference culture methods for any of the three surfaces tested, as determined by probability of detection analysis.

CONCLUSIONS

The Listeria Right Now method is an effective procedure for the detection of Listeria spp. from a variety of environmental surfaces.

HIGHLIGHTS

Listeria Right Now provides accurate results, without enrichment, in real time. This enables food industry personnel to react swiftly to suspected Listeria contamination incidents.

Predicting tearing paths in thin sheets

This study investigates the tearing of a thin notched sheet when two points on the sheet are pulled apart. The concepts that determine the crack trajectory are reviewed in the general anisotropic case, in which the energy of the fracture depends on the fracture direction. When observed as a flat sheet a purely geometric "tearing vector" is defined through the location of the crack tip and the pulling points. Both Griffiths's criterion and the maximum energy release rate criterion (MERR) predict a fracture path that is parallel to the tearing vector in the isotropic case. However, for the anisotropic case, the application of the MERR leads to a crack path that deviates from the tearing vector, following a propagation direction that tends to minimize the fracture energy. In the case of strong anisotropy, it is more difficult to obtain an analytical prediction of the tearing trajectory. Thus, simple geometrical arguments are provided to give a derivation of a differential equation accounting for crack trajectory, according to the natural coordinates of the pulling, and in the case that the anisotropy is sufficiently weak. The solution derived from this analysis is in good agreement with previous experimental observations.

Reveal Q+ MAX® for Detection of Total Af latoxin in Corn, Almonds, Pistachios, Walnuts, and Peanuts

Background: The Reveal Q+ MAX for Aflatoxin is a lateral flow immunochromatographic test intended for quantitative analysis within 6 min after aqueous extraction. Objective: Work was conducted to validate the performance of the Reveal Q+ MAX for Aflatoxin method in selected corn and nut matrixes. Methods: This method was validated under the requirements of the AOAC Research Institute Performance Tested Method^SM program. Five matrixes, including corn naturally contaminated with aflatoxin at 0, 5.2, 21.0, 51.6, 103.6, and 282 ppb as well as peanuts, pistachios, walnuts, and almonds spiked at 0, 5, 20, 50, and 300 ppb were analyzed. Results: Average percentage recoveries of the added aflatoxin from the matrixes ranged from 80.8 to 116.9%. Average LOD for all matrixes is 2 ppb and LOQ is 7 ppb. With the exception of sample size for almonds, robustness trials demonstrated that deliberate changes to the assay parameters minimally affected the Reveal Q+ MAX assay performance. Finally, stability results from three independently manufactured lots support Reveal Q+ MAX for Aflatoxin performance consistency and shelf-life of 18 months when stored at room temperature. Conclusions: This study appropriately validates the Performance Tested MethodSM claim for corn and selected nut matrixes on Reveal Q+ MAX for Aflatoxin, an aqueous lateral flow test kit. Highlights: Aqueous lateral flow test kit detects total aflatoxin between 80 to 120% yield with an LOD of 2 ppb.

Validation of a Modified ANSR® for E. coli O157:H7 Method for Detection of E. coli O157:H7 in Select Foods

Background: The ANSR method is based on isothermal nucleic acid amplification technology. The modifications to assay components improve sensitivity of the assay and robustness of the internal positive control. Objective: A Performance Tested MethodSM validation study was conducted to assess performance of a modified version of the ANSR® for Escherichia coli O157:H7 method. Methods: The validation study included inclusivity/exclusivity, matrix, robustness, accelerated stability, and independent laboratory testing. Results: In inclusivity testing of 55 strains of E. coli O157:H7 and E. coli O157:NM variants, all strains produced positive results. In exclusivity testing of 41 strains including E. coli of other serotypes and bacteria of closely related genera, all strains produced negative results. In matrix testing of beef trim, raw ground beef, spinach, and sprout-irrigation water, ANSR method performance was compared with that of the U.S. Department of Agriculture Food Safety and Inspection Service Microbiology Laboratory Guidebook or the U.S. Food and Drug Administration Bacteriological Analytical Manual reference culture procedures. Conclusions: all trials, ANSR method performance was not statistically different from that of the reference methods. Results of independent laboratory testing of ground beef corroborated those of internal testing. Introducing modest changes to three assay operating parameters did not materially affect ANSR method performance. Finally, accelerated stability testing results of three independently manufactured lots of ANSR reagents support a shelf-life of 1 year when stored at 2-8°C.

Stress defocusing in anisotropic compaction of thin sheets

We address the crumpling of thin sheets in between large scale curved cylinders. In contrast with the usual crushing of a paper ball, one curvature of the sheet is fixed here by the cylinders radius, yielding an anisotropic compaction. As compaction proceeds, it is found that sheets first develop singular folds involving ridges or developable cones, but eventually turn to regular folds free of any geometrical singularities, without ever having entered the plastic regime. This surprising uncrumpling transition corresponds to a stress defocusing. It is understood from a balance between bending and stretching energies on regular states.

Elasto-capillarity: deforming an elastic structure with a liquid droplet

Although negligible at macroscopic scales, capillary forces become dominant as the sub-millimetric scales of micro-electro-mechanical systems (MEMS) are considered. We review various situations, not limited to micro-technologies, where capillary forces are able to deform elastic structures. In particular, we define the different length scales that are relevant for 'elasto-capillary' problems. We focus on the case of slender structures (lamellae, rods and sheets) and describe the size of a bundle of wet hair, the condition for a flexible rod to pierce a liquid interface or the fate of a liquid droplet deposited on a flexible thin sheet. These results can be generalized to similar situations involving adhesion or fracture energy, which widens the scope of possible applications from biological systems, to stiction issues in micro-fabrication processes, the manufacturing of 3D microstructures or the formation of blisters in thin film coatings.

Localization through surface folding in solid foams under compression

We report a combined experimental and theoretical study of the compression of a solid foam coated with a thin elastic film. Past a critical compression threshold, a pattern of localized folds emerges with a characteristic size that is imposed by an instability of the thin surface film. We perform optical surface measurements of the statistical properties of these localization zones and find that they are characterized by robust exponential tails in the strain distributions. Following a hybrid continuum and statistical approach, we develop a theory that accurately describes the nucleation and length scale of these structures and predicts the characteristic strains associated with the localized regions.

How many children and adolescents in Spain comply with the recommendations on physical activity?

AIM

Physical inactivity is likely one of the main causes of obesity and other chronic diseases. This study shows descriptive data on physical activity and compliance with the health enhancing physical activity recommendations for children and adolescents and the determining factors among the Spanish population.

METHODS

The population of the study was enrolled for the enKid study, a cross-sectional study carried out on a representative sample of Spanish children, adolescents and youth to evaluate nutritional status and food intake. A subsample of the enKid study including individuals from 6 to 18 years was evaluated for compliance with the recommendation for health enhancing physical activity.

RESULTS

The results showed that only 48% of individuals from 6 to 18 years did at least 60 minutes of physical activity daily. Forty nine percent of girls and 37% of boys did not practice any sports during their leisure time. The percentage of active people diminishes as they get older, especially with reference to girls. Social status and mother's educational level act positively on the level of physical activity of the population.

CONCLUSION

Exercise is not a widespread leisure time activity in Spanish children and youth and few individuals did enough exercise for health promotion. Public health campaigns should take into account socio-economic variables and improve the access to sports facilities.

Cracks in thin sheets: when geometry rules the fracture path

We study the propagation of brittle fractures coupled to large out-of-plane bending, as when a brittle elastic thin sheet is cut by a moving object. Taking into account the separation of the film's bending and stretching energies and using fracture theory we show that such cracks propagate according to a simple set of geometrical rules in the limit of small thickness. In particular, this provides some insight into the geometrical origin of the oscillatory fracture patterns reported in two recent experiments. Numerical integration of our geometrical rules accurately reproduces both the shape of the fracture pattern and the detailed time evolution of the propagation of the crack tip, for various geometries of the cutting object.

Noise induced bistability of parametric surface waves

We report an experimental study on the effect of an external multiplicative noise on a subcritical bifurcation leading to the parametric amplification of surface waves. We show that the probability density function of the wave amplitude in the presence of noise has two maxima that do not correspond to any of the deterministic states. When the deterministic forcing is varied in the presence of noise, these most probable values give two new branches in the bifurcation diagram that involve a much larger difference in oscillation amplitude. The bistable region is also strongly enlarged. This noise induced bistability can be understood in the general framework of noise induced transitions.

Incentives for teaching psychiatry

A questionnaire was sent to chairs and faculty in 137 academic departments of psychiatry regarding the methods used to promote teaching and their perceived value. The incentives most often used included promotion and retention, nomination to committees, and peer recognition. Least often used were bonuses and a designated teachers' career track. Chairs and their faculty often disagreed as to whether some incentives were being used at all Recognition of teaching excellence was generally most highly valued as a useful incentive. Clarification of the nature and purpose of teaching incentives would likely improve their effectiveness.

[Neonatal choledocholithiasis: a case report]

Cholelithiasis as cause of jaundice in newborn is rare. Usually is associated with known predisposing factors as hemolysis, congenital anomalies of biliary tree, total parenteral nutrition, prolonged fasting. However there are recent signals in literature about idiopathic neonatal cholelithiasis, that seems to be more common than previously suspected. We describe a case of idiopathic neonatal choledochal lithiasis with spontaneous resolution in few days from jaundice beginning. The importance of ultrasonographic investigation for diagnosis and follow-up is confirmed. However, because it is often a self limiting phenomenon, an aggressive approach is not warranted in the asymptomatic infant.

Liver disease in cystic fibrosis

Liver disease associated with cystic fibrosis (CF) is considered a secondary effect of the basic defect of the disease, leading to obstruction of bile ductules by abnormal mucoid secretions; additional factors have been involved in the pathogenesis, such as abnormalities in bile acid metabolism, nutritional deficiencies, drug hepatotoxicity, stenosis of the common bile duct by the fibrotic pancreas. Clinical presentation of liver disease in CF is rare during the first few years of life, although neonatal cholestasis can be occasionally the first manifestation of the disease. Isolated massive steatosis has been reported in less than 5% of cases as a consequence of malnutrition. Focal biliary cirrhosis is the pathognomonic hepatic lesion and is present in 25-30% of CF patients, most of whom are asymptomatic. The focally distributed lesions can extend leading to multi-lobular biliary cirrhosis with occurrence of signs and symptoms of cirrhosis and portal hypertension. Early diagnosis of CF-associated liver disease is difficult since liver function tests may be normal even in cases of overt cirrhosis: no test has proved to be sufficiently sensitive and specific and even liver biopsy is of questionable relevance due to the focal distribution of hepatic lesions. Clinical examination is of major importance, since the presence of hepatomegaly seems to correlate well with the histologic finding of fibrosis. The rationale for the use of the choleretic non-toxic bile acid ursodeoxycholic acid in CF-associated liver disease is to reduce the viscosity of bile and to replace toxic bile acids which accumulate in the hepatocyte.(ABSTRACT TRUNCATED AT 250 WORDS)

A Case of Carcinoma of the Colon Associated with Schistosomiasis (Bilharziosis) in a Young Woman

Images