The physiology of germination and dormancy in seeds of gynandropsi gynandra L. Briq syn Cleome gynandra L. (Cleomaceae).

Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.The “spider plant” Gynandropsis gynandra L. Briq,” is an important traditional leafy vegetable in many parts of Africa. The species is considered underutilized and has been mainly neglected by research systems. Yields are generally low and this has been attributed to a number of factors including low and non-uniform seed germination. This study sought to gain a deeper understanding of factors influencing germination and dormancy in spider plant seeds. The specific objectives were to, (i) describe and document the phenotypic characteristics and mineral composition of seeds of 29 G. gynandra accessions from diverse regions, (ii) determine the pattern of seed germination and dormancy development in seeds of different spider plant accessions and their crosses and (iii) assess the storage potential of spider plant seeds using artificial aging. To achieve these objectives, accessions originating from West Africa, East Africa and Asia were used. In the first experiment, seeds of the accessions from the three regions were subjected to scanning electron microscopy to study seed structure and mineral composition. In the second experiment, seeds from different accessions were planted in pots in a tunnel and data recorded at bi-weekly intervals during development until maturity on the following variables: seed fresh and dry mass, seed moisture content, germination capacity, mean germination time (MGT) and electrical conductivity (EC). In the third experiment, seeds that had been stored for four months and freshly harvested were subjected to the accelerated aging to test for storage potential. The same variables that were in the second experiment were measured in the third experiment in addition to tetrazolium test (TZ). Data analysis was done using R software version 3.5.1. Eight mineral elements were identified in the seeds of spider plant, and the internal and external structure of the seed was revealed. The results showed significant differences among spider plants accessions with regard to shape, size, mineral composition, germination percentage and mean germination with Asian accessions showing a higher germination percentage. The study revealed that spider plant fresh seeds exhibited a physiological dormancy which can be broken by heating at 41°C for 3 days and/or gibberellic acid (0.001%), depending on the genotype. However, the degree of dormancy varied from one genotype to another as follows: weak (% germination >50%), intermediate (% germination>6%<50%) and strong (% germination<6%). Moreover, the study found that a saturated solution of 40% NaCl for 48 h could be used to evaluate the physiological quality in spider plant seeds during storage. It is suggested that further experiments using the diversity observed in the species be conducted to select genotypes with weak dormancy in order to improve the germination capacity in the species

A Comparative Study of Inspection Techniques for Array Packages

This viewgraph presentation reviews the inspection techniques for Column Grid Array (CGA) packages. The CGA is a method of chip scale packaging using high temperature solder columns to attach part to board. It is becoming more popular over other techniques (i.e. quad flat pack (QFP) or ball grid array (BGA)). However there are environmental stresses and workmanship challenges that require good inspection techniques for these packages

Experimental investigation and ANN prediction for part quality improvement of fused deposition modeling parts

Fused deposition modeling (FDM) is the most prevalent thermoplastic additive manufacturing technology. Many input parameters and their settings have a significant impact on the quality and functionality of FDM parts produced. To enhance the quality of parts, it is critical to be able to predict surface roughness distribution in advance. The development of artificial neural network (ANN) models to forecast the impact of main FDM process factors on the part quality in terms of surface roughness while utilizing ABS (Acrylonitrile butadiene styrene) material is described in this work. Taguchi L9 orthogonal array was used to plan the experiments. Different printing input parameters such as layer thickness, orientation angle, and infill angle are used in the experiments. In terms of controllable input parameters, ANN is used to construct a predictive mathematical model. The effects of various printing settings on surface roughness were investigated using analysis of variance (ANOVA), main effect plots, and contour plots. Experiment findings and regression value are used to validate the models. The model has shown to be capable of adequately predicting responses within a maximum percentage error of 4.664 percent of arithmetic roughness average (Ra), which is a good agreement.publishedVersio

ANALISIS KEPADATAN MAKROALGA DI PERAIRAN PANTAI DESA BOLOK

Abstrak - Makroalga dikenal juga sebagai rumput laut merupakan tumbuhan thallus (Thallophyta) dimana organ-organ berupa akar, batang, dan daunnya belum terdiferensiasi dengan jelas. Keberadaan makroalga sebagai organisme produser memberikan sumbangan yang berarti bagi kehidupan organisme akuatik terutama organisme-organisme herbivora (hewan–hewan laut) di perairan laut. Penelitian ini bertujuan untuk menganalisis Kepadatan dari makro alga di perairan Pantai Desa Bolok. Diharapkan penelitian ini dapat memberikan informasi bagi pengembangan ilmu pengetahuan khususnya ekologi perairan pesisir dan dalam bidang perikanan pada umumnya. Metode survey digunakan dalam pengumpulan data dengan menggunakan garis transek dengan teknik sampling kuadran. Komposisi jenis makroalga yang ditemukan di perairan Pantai Desa Bolok sejumlah 11 spesies yaitu 4 spesies dari kelas Chlorophyta, 3 spesies dari kelas Phaeophyta, dan 4 spesies dari kelas Rhodophyta. &nbsp;Kepadatan spesies tertinggi di daerah Bolok terdapat pada spesies Ulva reticulata dengan nilai kepadatan spesies 50,42 individu/m2 di perairan Pantai Desa Bolok, kepadatan spesies terkecil di perairan Pantai Bolok terdapat pada spesies Padina minor dengan nilai kepadatan 1,46 individu/m2. Kata Kunci : Makroalga, Kepadatan, Desa Bolok, Zona Intertidal

Degradation of Multi-Layer Insulation (MLI) Retrieved from the Hubble Space Telescope

Multi-Layer Insulation (MLI) returned during Servicing Mission 4 are still being analyzed. Analysis has revealed degradation of optical, thermal, and mechanical properties, increased crystallinity, and reduction in fluorine/carbon ratio of aluminized-Teflon fluorinated ethylene propylene (Al-FEP) FEP. These material properties can be affected by high temperatures on orbit, increased radiation exposure, and in some cases contamination from materials in close proximity to the insulation on orbit. Preliminary results support conclusions of previous studies: areas of Al-FEP that received higher levels of solar exposure show more degradation (high temperatures and radiation combined)

Analyses of Hubble Space Telescope Aluminized-Teflon Multilayer Insulation Blankets Retrieved After 19 Years of Space Exposure

Since its launch in April 1990, the Hubble Space Telescope (HST) has made many important observations from its vantage point in low Earth orbit (LEO). However, as seen during five servicing missions, the outer layer of multilayer insulation (MLI) has become increasingly embrittled and has cracked in many areas. In May 2009, during the 5th servicing mission (called SM4), two MLI blankets were replaced with new insulation and the space-exposed MLI blankets were retrieved for degradation analyses by teams at NASA Glenn Research Center (GRC) and NASA Goddard Space Flight Center (GSFC). The retrieved MLI blankets were from Equipment Bay 8, which received direct sunlight, and Equipment Bay 5, which received grazing sunlight. Each blanket was divided into several regions based on environmental exposure and/or physical appearance. The aluminized-Teflon (DuPont, Wilmington, DE) fluorinated ethylene propylene (Al-FEP) outer layers of the retrieved MLI blankets have been analyzed for changes in optical, physical, and mechanical properties, along with chemical and morphological changes. Pristine and as-retrieved samples (materials) were heat treated to help understand degradation mechanisms. When compared to pristine material, the analyses have shown how the Al-FEP was severely affected by the space environment. Most notably, the Al-FEP was highly embrittled, fracturing like glass at strains of 1 to 8 percent. Across all measured properties, more significant degradation was observed for Bay 8 material as compared to Bay 5 material. This paper reviews the tensile and bend-test properties, density, thickness, solar absorptance, thermal emittance, x-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) elemental composition measurements, surface and crack morphologies, and atomic oxygen erosion yields of the Al-FEP outer layer of the retrieved HST blankets after 19 years of space exposure

Origin-dependence of variation in seed morphology, mineral composition and germination percentage in Gynandropsis gynandra (L.) Briq. accessions from Africa and Asia

Background: Spider plant [Gynandropsis gynandra (L.) Briq.], an economically promising African leafy vegetable, characterized for leaf yield components and nutritive quality, exhibits poor seed germination that hinders a wider expansion of the crop in urban and periurban horticultural systems. So far, there is little information pertaining to seed morphological traits and mineral elements content that may be associated with higher seed germination. This research investigated the hypothesis that spider plants from different geographical areas exhibited differences in seed mineral composition, morphological traits, and germination capacity. To this end, twenty-nine accessions of Gynandropsis gynandra from West and East-Southern Africa, and Asia were screened for variation in seed size (area, perimeter, length, width), 10-seed weight, mean germination time, germination percentage and mineral content variations. The scanning electron microscopy (SEM), light microscopy and energy dispersive spectroscopy (EDS) solution were used to study seed morphology and mineral composition. Results: We show for the first time the external and internal structure of the seeds of Gynandropsis gynandra and measured eight mineral elements, including carbon (C), oxygen (O), magnesium (Mg), aluminium (Al), phosphorus (P), sulphur (S), potassium (K) and calcium (Ca). The accessions differed significantly (p < 0.001) with respect to seed size (area, perimeter, length, width), 10-seed weight, mean germination time and germination percentage. The hierarchical cluster analysis based on fourteen variables grouped the accessions into three distinct clusters, partially dependent on their geographical origin. Asian accessions exhibited smaller seeds and recorded higher values in terms of germination percentage. West African accessions had bigger seeds but with lower germination percentage. Variation in minerals such as potassium, carbon, and calcium content showed different patterns according to geographical origins. Conclusion: Smaller seeds in G. gynandra exhibited better germination capacity. The Asian germplasm is a potential source of cultivars with a higher germination percentage for improving seed quality in the species.</p

Analyses of Hubble Space Telescope Aluminized-Teflon Insulation Retrieved After 19 Years of Space Exposure

Since its launch in April 1990, the Hubble Space Telescope (HST) has made many important observations from its vantage point in low Earth orbit (LEO). However, as seen during five servicing missions, the outer layer of multilayer insulation (MLI) has become successively more embrittled and has cracked in many areas. In May 2009, during the 5th servicing mission (called SM4), two MLI blankets were replaced with new insulation pieces and the space-exposed MLI blankets were retrieved for degradation analyses by teams at NASA Glenn Research Center (GRC) and NASA Goddard Space Flight Center (GSFC). The MLI blankets were from Equipment Bay 8, which received direct sunlight, and Equipment Bay 5, which received grazing sunlight. Each blanket contained a range of unique regions based on environmental exposure and/or physical appearance. The retrieved MLI blanket s aluminized-Teflon (DuPont) fluorinated ethylene propylene (Al-FEP) outer layers have been analyzed for changes in optical, physical, and mechanical properties, along with space induced chemical and morphological changes. When compared to pristine material, the analyses have shown how the Al-FEP was severely affected by the space environment. This paper reviews tensile properties, solar absorptance, thermal emittance, x-ray photoelectron spectroscopy (XPS) data and atomic oxygen erosion values of the retrieved HST blankets after 19 years of space exposure

Current-induced highly dissipative domains in high Tc thin films

We have investigated the resistive response of high Tc thin films submitted to a high density of current. For this purpose, current pulses were applied into bridges made of Nd(1.15)Ba(1.85)Cu3O7 and Bi2Sr2CaCu2O8. By recording the time dependent voltage, we observe that at a certain critical current j*, a highly dissipative domain develops somewhere along the bridge. The successive formation of these domains produces stepped I-V characteristics. We present evidences that these domains are not regions with a temperature above Tc, as for hot spots. In fact this phenomenon appears to be analog to the nucleation of phase-slip centers observed in conventional superconductors near Tc, but here in contrast they appear in a wide temperature range. Under some conditions, these domains will propagate and destroy the superconductivity within the whole sample. We have measured the temperature dependence of j* and found a similar behavior in the two investigated compounds. This temperature dependence is just the one expected for the depairing current, but the amplitude is about 100 times smaller.Comment: 9 pages, 9 figures, Revtex, to appear in Phys. Rev.

Normal-superconducting transition induced by high current densities in YBa2Cu3O7-d melt-textured samples and thin films: Similarities and differences

Current-voltage characteristics of top seeded melt-textured YBa2Cu3O7-d are presented. The samples were cut out of centimetric monoliths. Films characteristics were also measured on microbridges patterned on thin films grown by dc sputtering. For both types of samples, a quasi-discontinuity or quenching was observed for a current density J* several times the critical current density Jc. Though films and bulks much differ in their magnitude of both Jc and J*, a proposal is made as to a common intrinsic origin of the quenching phenomenon. The unique temperature dependence observed for the ratio J*/Jc, as well as the explanation of the pre-quenching regime in terms of a single dissipation model lend support to our proposal.Comment: 10 pages, 10 figures, submitted to Physical Review