The mechanical properties of lettuce: A comparison of some agronomic and postharvest effects

Mechanical properties data of Iceberg lettuce leaves are described in relation to the applied agronomic variables and post-harvest treatment. Leaf tissue strength and stiffness were both reduced significantly in plants grown with 120 kg/ha applied nitrogen compared with plants grown with 0 kg/ha applied nitrogen. Leaf tissue strength and stiffness were increased significantly in plants grown with added calcium at 80 kg/ha. Significant reductions in stiffness and increases in failure strain were associated with reduced hydration. These findings show that agronomy changes in mechanical properties are as large as maturity and post harvest induced turgor changes, which has implications for both quality and damage of cut salads.     

Thermal resistance between powdered cerium magnesium nitrate and liquid helium at very low temperatures

Experiments have been performed from magnetic temperatures of 2–20 mK on the effect of minute⁴He impurities and a magnetic field on the thermal resistance between powdered cerium magnesium nitrate (CMN) and liquid³He. The thermal resistance decreases with decreasingT and increasing small field but is increased dramatically at a givenT by the addition of roughly a monolayer of⁴He. The resistance is interpreted as resulting from a surface magnetic coupling between CMN and liquid³He.This work has been supported by the U.S. Atomic Energy Commission under Contract No. AT(04-3)-34, P.A. 143, and by the Air Force Office of Scientific Research, Office of Aerospace Research, United States Air Force, under Grant No. AF-AFOSR-631-67A.     

Alleged acceptance of the occupational role of teaching.

At the beginning of graduate training, 122 inexperienced liberal arts graduates took a questionnaire dealing with acceptance of teaching as an occupation. They were studied 2 years later after having had a year in teaching. An Index was determined for 3 groups according to degree of permanancy in teaching. "The Index has a small predictive validity, but only for the women in the sample." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Video-assisted thoracoscopic placement of paravertebral catheters: a technique for postoperative analgesia for bilateral thoracoscopic surgery

Paravertebral catheters were placed bilaterally through a Tuohy needle under direct video control in a patient undergoing video-assisted thoracoscopic (VAT) surgery for recurrent, bilateral pneumothoraces. Postoperative analgesia was produced by infusing bupivacaine through the catheters. This provided good analgesia. VAT placement of paravertebral catheters is easily accomplished and may be a part of the surgical procedure.     

Ultrasonic assisted enzymatic digestion (USAED) coupled with high performance liquid chromatography and electrothermal atomic absorption spectrometry as a powerful tool for total selenium and selenium species control in Se-enriched food supplements

The suitability of hyphenated USAED with HPLC separation and ET-AAS determination as a new rapid methodology for Se control in Se-enriched food supplements is demonstrated. Total Se determination and Se speciation are accomplished in a single sample treatment using low sample amounts (ca. 10 mg), and low extracting volume (1 mL). The total Se content in seven of the 10 Se-enriched supplements studied was in agreement with the values obtained after microwave pressurized acid digestion, MW, (test t, p = 0.05). The Se species studied were Se(IV), Se(VI), SeMet, SeMeSeCys, and SeCys₂, being some of the most common found in the 10 supplements studied. Although SeMet was the Se species expected to be present at the highest concentration in most Se-enriched food supplements, we detected it in only three of the 10 samples studied. In the other seven samples, two of them had Se(IV) as the main Se species. The other five supplements had Se species that did not match with any of the five standards selected by us. We have also systematically demonstrated that ultrasonication does not alter the following Se species: Se(IV), Se(VI), SeMet, SeMeSeCys, and SeCys₂. The new procedure can be easily adapted to more Se species and can be routinely used for Se control in Se-enriched food supplements. Concerning the supplements studied, our results suggest that stricter control on the Se content in enriched food supplements in terms of Se species will need to become mandatory.     

The effects of temperature,chlorine and acids on the survival of Listeria and Salmonella strains associated with uncooked shrimp carapace and cooked shrimp flesh

The purpose of this study was to assess the influence of the association of Listeria and Salmonella with shrimp surfaces on the effects of temperature, chlorine and acids on their survival. Planktonic, attached and colonized cells of Listeria monocytogenes Scott A, L. monocytogenes V7, Salmonella Senftenberg 1734b and S. Typhimurium ATCC 14028 were challenged with high (50°, 60° and 70 °C) and low (4 °C) temperature, 100 ppm sodium hypochlorite solution, and acetic, hydrochloric and lactic acids (pH 4.0). Attached and colonized Listeria and Salmonella showed significantly greater (p < 0.05) resistance to heat (∼1.3–2.6 fold increase in D-values), hypochlorite (∼6.6 ≥ 40.0 fold) and acids (∼4.0–9.0 fold) than their planktonic counterparts. There were no significant differences (p > 0.05) in the survival of planktonic, attached or colonized cells of Listeria and Salmonella stored under refrigerated conditions. The association of Listeria and Salmonella with shrimp surfaces enhances their resistance to heat, chlorine and acids. Both attachment to, and subsequent colonization of, shrimp surfaces by pathogens may reduce the efficacy of methods used in their control. Strategies to reduce attachment of these pathogens to shrimp are required to assure safety of this product.     

Solution blow spun titania nanofibers from solutions of high inorganic/organic precursor ratio

In this work titania nanofibers were produced from different precursor solutions by solution blow spinning. Hydrophilic polyvinylpyrrolidone, hydrophobic poly(vinyl acetate) and amorphous and semi-crystalline poly(lactic acid) polymers were used with green-solvents and titanium isopropoxide as the inorganic precursor. Hybrid nanofibers with high inorganic loading content were successfully produced from all precursor solutions. The fibers were calcined at different annealing temperatures for evaluation of phase transitions. The minimum temperature to obtain pure titania fiber was found to be 500 °C, as assessed by thermal characterization. Anatase was the unique polymorph formed at this annealing temperature. This is of paramount importance due to its photocatalytic character. Calcination at high temperatures showed that rutile slightly appeared at 600 °C for the polyvinylpyrrolidone-based system and showed a strong peak at 700 °C for all systems, co-existing with anatase as minor phase. The use of amorphous and semicrystalline poly(lactic acid) polymers did not influence the anatase crystal size and phase conversion. This was found to be dependent on the annealing temperature and medium acidity, as currently found in powder synthesis.