Gas chromatography–mass spectrometry analyses of encapsulated stable perovskite solar cells

Although perovskite solar cells have produced remarkable energy conversion efficiencies, they cannot become commercially viable without improvements in durability. We used gas chromatography–mass spectrometry (GC-MS) to reveal signature volatile products of the decomposition of organic hybrid perovskites under thermal stress. In addition, we were able to use GC-MS to confirm that a low-cost polymer/glass stack encapsulation is effective in suppressing such outgassing. Using such an encapsulation scheme, we produced multi-cation, multi-halide perovskite solar cells containing methylammonium that exceed the requirements of the International Electrotechnical Commission 61215:2016 standard by surviving more than 1800 hours of the Damp Heat test and 75 cycles of the Humidity Freeze test.

Study of Tensile Bond Strength for Structural Silicone Sealants after Artificial Accelerated Aging

Tensile bond strength is one of the most significant properties for structural silicone sealants used in the glass curtain walls. During the service process, aging of the silicone sealants shall be involved in comprehensive actions of environment factors, e.g. temperature, humidity, and ultraviolet light etc. In this study, artificial accelerated aging test was conducted to make clear the development of tensile bond strength, Shore hardness and elongation. The test results show that: (i) the specimens under damp-heat test have more degeneration than specimens under humidity-freeze test; (ii) the environment of high temperature and high humidity leads to the change of tensile bond, Shore hardness, elongation, and results in interfacial failure of samples.

Freezability of Andalusian donkey (Equus asinus) spermatozoa: effect of extenders and permeating cryoprotectants

The aim of this study was to compare the effect of two semen extenders and four permeating cryoprotectants on post-thaw sperm quality of Andalusian donkeys. First, 32 ejaculates were pooled, split and frozen in either Gent B or INRA 96 with egg yolk and glycerol. Second, 12 pooled semen samples were simultaneously frozen in Gent B (glycerol) or Gent A containing ethylene glycol (EG; 1 or 1.5%) or dimethyl sulfoxide (DMSO; 1.5 or 2%). Finally, nine pooled samples were simultaneously cryopreserved in Gent A containing 1% EG (as control), dimethylformamide (DMFA; 1 or 2.5%) or a combination of 1% EG and 1.5% DMFA. Gent B yielded a higher (P < 0.01) post-thaw sperm motility than modified INRA96. EG 1% increased the sperm membrane integrity (P < 0.001), whereas DMSO affected sperm motility and membrane integrity (P < 0.001). DMFA 2.5% yielded higher (P < 0.001) values for sperm motility and membrane integrity. We concluded that Gent B improves in vitro post-thaw sperm quality of donkey spermatozoa, but the replacement of glycerol with 1% EG or 2.5% DMFA increased sperm protection against cryodamage. The use of DMSO for freezing donkey semen was unsuccessful and a toxic effect is suspected. These extenders should be included in the pre-freeze test for each donkey.

An evaluation of freezing tolerance of winter chickpea (Cicer arietinum L.) using controlled freeze tests

Nezami, A., Bandara, M. S. and Gusta, L. V. 2012. An evaluation of freezing tolerance of winter chickpea ( Cicer arietinum L.) using controlled freeze tests. Can. J. Plant Sci. 92: 155–161. Chickpeas (Cicer arietinum L.) are subject to freezing injury and/or winter kill. Field testing for freezing tolerance evaluation is slow, unreliable, and highly variable; thus an artificial freeze test that correlates with field survival is required. Our objective was to develop a reliable and simple artificial freeze test to evaluate the freezing tolerance of winter chickpeas. Four cultivars with varying levels of freezing tolerance were grown and cold acclimated under low irradiance (150 µmol m−2 s−1) and high irradiance (400 µmol m−2 s−1). Acclimated whole plants or excised leaflets were subjected to six tests to determine the LT50 temperature (lowest temperature to kill 50% of the plants). In two tests, following the freeze test, whole plants were held at 20°C/15°C (day/night) for 3 wk for re-growth analysis. LT50 was estimated from both axillary buds and foliage re-growth and from foliage re-growth. The LT50 was also assessed on excised plantlets from whole plants frozen to a series of test temperatures. LT50 was determined by re-growth of plantlets held for 1 wk at 20°C in test tubes or by electrolyte leakage following thawing at 20°C. Excised plantlets were frozen to the same temperatures used for the whole plants. LT50 was determined by re-growth in test tubes for 1 wk or by electrolyte leakage. Results from excised plant parts from frozen intact plants or plantlets excised prior to the freeze test were similar to those estimates derived from re-growth analysis of plants frozen whole. Freeze test employing excised plantlets offers high precision and the ability to screen large populations. Plants grown and cold acclimated under an irradiance of 150 µmol m−2 s−1 were not as freezing tolerant as those grown and cold acclimated under an irradiance of 400 µmol m−2 s−1.

Evaluation of Deciduous Azaleas for Cold Hardiness Potential in the Southeastern United States

Twelve taxa of deciduous azalea were evaluated using laboratory procedures to determine hardiness of stems and flower buds. Rhododendron atlanticum, ‘My Mary’, ‘Nacoochee’, and ‘TNLV1’ exhibited the greatest stem cold hardiness, surviving to at least −29C ± 1 (−20F ± 2) in February 1996. Rhododendron oblongifolium exhibited the least stem cold hardiness, surviving to only −11C ± 1 (10F ± 2). All results were consistent with previous field studies. Except for R. viscosum and R. serrulatum, lowest survival temperatures for stems were analogous to reports available in the literature. Rhododendron viscosum and ‘My Mary’ had the lowest survival temperature recorded for flower buds, −23C ± 1 (−9F ± 2), in February 1998 and February 1999, respectively, though not significantly different than most other taxa examined. Lowest survival temperatures for flower buds varied from published accounts, with buds in the present study being less hardy than previously reported. Differences from published reports in the lowest survival temperatures of stems and flower buds are attributed to provenance, temperature fluctuations, cultural effects on the plants, and differences among freeze test protocols.

Screening lentil (Lens culinaris) for cold hardiness under controlled conditions

This study describes the development of a highly repeatable cold screening procedure for lentil (Lens culinaris Medik.) using controlled conditions which involve first, acclimation of the plants at the vegetative stage in a growth chamber and second, freeze testing in a freeze chamber. The seeds were first germinated in Petri dishes and then planted in styrofoam trays with individual cells. Initial growing temperatures in the growth chamber for two weeks were 25 °C day and 10 °C night with a 12 h photoperiod. In the third week the photoperiod was changed to 10 h and in the fourth the temperatures were changed to 10 °C day and 0 °C night to acclimate the plants. Using a modified freeze chamber (household deep freezer), a freeze test temperature of −15 °C, following a 6–8 weeks acclimation period (because both acclimation times had the same effect for cold tolerance of the genotypes), at 2 and 3 °C/h cooling rate, and an exposure time of 3 h at −15 °C were appropriate to detect significant (P<0·01) differences among several lines at a comparatively low degree of injury for the most cold-hardy genotypes.

The selection of superior winter-hardy genotypes using a prolonged freeze test

Methods of assessing the freezing tolerance of winter cereals must be improved in order to distinguish small differences due to genotype or environment. Seed of eight winter wheat (Triticum aestivum L. em Thell) cultivars, ranging in winter hardiness, were sown either in mid-August, the first week of September or mid-September. Individual plants of each were collected in late October and stored at either −4° or −8 °C. In December controlled freeze tests, employing a cooling rate of 2 °C h−1, could not distinguish the less freezing-tolerant cultivars stored at −4 °C. However, by March the less winter-hardy cultivars from the third seeding date stored at −4 °C could be distinguished. Seedlings stored at −8 °C declined in freezing tolerance more rapidly than seedlings stored at −4 °C. In December, the less hardy winter wheat cultivars, Rose, Rita and Siouxland, were less freezing tolerant than the hardy cultivars (e.g. Norstar). Seedlings of Rita and Siouxland from the second and third seeding date died by February when stored at −8 °C. Seedlings of all winter wheat cultivars were dead by March, except Norstar and Alabaskaja, the most winter-hardy cultivars. Storage of seedlings of wheat, triticale (× Triticosecale Rimpani Wit.) and rye (Secale cereale L.) at either −12° or −15 °C readily identified the superior winter-hardy genotypes. For example, in mid-winter both Siouxland and Norstar winter wheat had a similar LT50 (temperature at which 50% of the plants are killed). However, Siouxland could not tolerate storage at either −12° or −15 °C for the same length of time as Norstar. These results support the theory that winter kill in nature is more a function of duration of exposure to sub-lethal temperatures rather than exposure to a minimum low temperature for a short duration as programmed in a conventional freeze test. A more realistic and precise freeze test would be to determine the ability of genotypes to survive lengthy exposure to sub-lethal low temperatures. Key words: Winter cereals, freezing tolerance, winter injury, duration effects, screening method

Evaluation of Frost Resistance Tests for Carbonate Aggregates

D-cracking is a progressive distress associated primarily with the use of coarse aggregates that deteriorate when they are critically saturated and subjected to repeated cycles of freezing and thawing. The present study was undertaken to consider better acceptance criteria for concrete aggregates and to allow for the use of more local Minnesota aggregates through selected aggregate beneficiation techniques. Condition surveys of concrete highway pavements were performed to document the field freeze-thaw performance of selected aggregate sources representing a range of frost resistance. Cores were obtained from these sections for laboratory testing and evaluation, and coarse aggregates were obtained from the original sources for use in performing environmental simulation tests [i.e., variations of ASTM C666 and the Virginia Polytechnic Institute (VPI) single-cycle slow-freeze test] and correlative tests (i.e., absorption and bulk specific gravity, Portland Cement Association absorption and adsorption tests, Iowa pore index test, acid insoluble residue test, X-ray diffraction analysis, X-ray fluorescence analysis, thermogravimetric analysis, and the Washington hydraulic fracture test). The tests that provided the best correlation with field performance included a modification of ASTM C666 Procedure B (specimens prepared with salt-treated aggregates), the VPI single-cycle slow-freeze test, and the Washington hydraulic fracture test. Other test procedures were correlated with field performance to lesser extents. It was noted that petrographic examination of pavement cores can help to distinguish between D-cracking and other conditions that can produce distresses with similar appearances (e.g., distresses caused by secondary mineralization, embedded shale, poor mix design, and alkali-aggregate reaction).

Freeze Tolerance of `Braeburn' Apple Shoots

Differential thermal analysis (DTA) and tetrazolium triphenyl chloride (TTC) were done on shoots of 4-year-old `Braeburn' apple trees for 3 years. The trees acclimated slowly in autumn. If cold temperatures last long enough in winter, shoots will acclimate as low as –40C. Shoots are sensitive to warm temperatures and deacclimated rapidly. An attempt to run a controlled test on freeze resistance of `Braeburn' did not respond to DTA. Moisture samples indicated trees were freeze dried. Different sets of trees were rehydrated and showed an exotherm pattern. Exotherms could be seen after 3 days at 26C, 14 days at 10C, and 21 days at 4C. Another controlled freeze test was performed on 1-year-old `Braeburn' trees. Trees were acclimated outdoors. An exotherm pattern could be seen upon DTA analysis. After artificial freezing, DTA and TTC tests showed pith killed at –24C, primarily xylem at –28C, and all tissue at –35C. After freezing, trees were placed in a greenhouse and warmed over 2 months. Upon dissection, we found xylem produced before freezing was dead, but a large amount of new xylem was generated. Trees appeared to have normal leaf and shoot growth for about a month, but eventually wilted and died. Dissection of these showed the same results as the first set dissected. New xylem evidently was not enough to carry the growth of the trees.