Recycled PET bottles for vacuum packaging
Vacuum packaging is a packaging technique intended to extend the shelf life of food via the removal of air from an enclosed package prior to sealing. This process limits the growth of aerobic bacteria or fungi due to oxygen deprivation. In this work, we present a novel do-it-yourself vacuum packaging device using the exchange of water and air between two bottles to continuously generate a vacuum-suction effect. The sizes of bottle and vacuum bag were investigated for its impact on the vacuum generation in a plastic bag containing smoked fish sausages. Large commercial 3.1-litre PET bottle generated more vacuum than the smaller ones. An equilibrated vacuum pressure of a smaller plastic bag was lower than that of a larger size. With 3.1-litre PET bottles, the vacuum pressure for 3”x5”, 5”x8” and 6”x9” bags was equilibrated at 8, 10, 18 mmHg, respectively. Sausages packaged by our device last for 14 days when they were kept in -20oC refrigerator, which was comparable to those packed by the commercial vacuum packaging system for household use. This project demonstrates an application of simple science in a real life situation as well as a promotion of environmental protection idea as the electricity is not used in the vacuum generation process and the disposed plastic bottles can be reused.
以簡易方法探討奈米銀的化學活性優於非奈米級銀粒子
A novel and simple method was developed to determine the activity of silver in nanometer particles more than in non-nanometer particles. The conductivity of conducting polymer, polyaniline (PANI) doped with different amount of nanometer silver particles was used to evaluated the activity of nanometer silver. In polymerization of polyaniline, hydrogen chloride solution usually used to increase the conductivity of polyaniline. When 1%(w/w) nanometer silver particles doped during the polymerization, the conductivity of polyaniline was down from 2.28 s/cm to 0.65 s/cm, then increased with increasing the amount of nanometer silver doped. The conductivity of polyaniline was changed from 2.28 s/cm to 0.47 s/cm when 3%(w/w) nanometer silver particles doped, but it is increased from 2.28 s/cm to 2.44 s/cm when was doped with 3%(w/w) micrometer silver particles. The conductivity of polyaniline changed due to the formation of silver chloride (AgCl) in doping nanometer silver. Some of the nanometer silver particles were formed to silver ion in hydrogen chloride solution for the high activity property of nanometer silver. This also can be proved from the spectra of XRD and FE-SEM. Therefore; determination the conductivity of conducting polymer by doping nanometer metal particles can be used to determine the activity of the nanometer particles. 本研究為開發一個新穎的檢測奈米金屬粒子化學活性大於非奈米金屬粒子的簡易方法。方法為利用導電高分子聚苯胺,於合成過程中添加不同濃度的奈米銀粒子,並分別偵測其成品的導電度,藉以評估奈米銀粒子的化學活性。由於聚苯胺在合成過程中通常加入鹽酸以提高其導電度,致活性較大的奈米銀粒子於氧化後,隨即與氯離子形成氯化銀的沉澱,而降低聚苯胺的導電度,如添加1﹪(w/w)奈米銀粒子的,其導電度由2.28 s/cm 降至0.65 s/cm,隨後隨著添加量的增加導電度先降後再稍回升。一般非奈米級銀粒子因氧化電位為負值,即化學活性小,而不易被氧化。由實驗結果,我們發現同樣添加3%(w/w)的奈米級銀粒子或微米級銀粒子,添加奈米級銀粒子的導電度由2.28 下降為0.47,添加微米級銀粒子的導電度卻由2.28 上升為2.44,此乃說明本方法確實足以證明奈米級金屬的化學活性的確遠大於微米級金屬,因相同條件下,微米級銀粒子未如同奈米級銀粒子一樣被氧化成銀離子。即奈米級銀粒子可以輕易的被氧化,而非奈米級銀粒子則不易被氧化。尤其也可由X 光繞射儀分析光譜圖和場發射式掃描電子顯微鏡拍攝圖證明。因此,我們可以採用添加3 %(w/w)奈米級金屬銀粒子及微米級金屬銀粒子於導電高分子的方法,並藉導電度的變化,證明奈米金屬粒子的高活潑性。
Research the efficiency of the fog-catching nets
Islands far from lands use the underground or surface water as the water for living. The population of the islands is growing fast and the amount of water usage is increasing year after year. However, the amount of water usage is limited, so that people who live in islands have trouble using water. To compensate this problem, underground water is drawn from deeper underground sites. If this matter occurs continuously, sea-level may rise and then we cannot use underground water. Seawater desalination is a way to solve the water shortage, but it requires a lot of energy. It is difficult for island far away from lands to supply a lot of energy. It is considered the eco-friendly way to minimize the use of energy on the island. In order to solve the problem of water shortage on the island, it is considered fog that on the island occur frequently. It is an attempt to create water from fog, but it is a lack of research of efficiency of fog-catching nets to create water from fog. In this research, I have studied the efficiency of the fog-catching nets, a way to increase the efficiency, the amount of water that is created on the island, usage of discarded fishing net for fog-catching nets. Through this research, I found a kind of fog which can be changed into water and the difference in efficiency due to the difference in the size of the mesh size of the fog-catching nets, wind direction, wind speed, water absorption capacity of thread of fog-catching nets, installation direction of fog-catching nets, a way of installation of fog-catching nets. Also I found fog-catching nets of discarded fishing nets on the island and the possibility of usage for everyday life that the amount of water are created for a day or a month during dry season on the island.
Up the Creek
After an annual swimming rally in the Nahoon river, concerns were raised after several swimmers fell ill, complaining of possible symptoms of mild E.coli infection. Research was hence conducted to determine the following: \r \r \r The Nahoon River is safe for recreational activity in terms of faecal-coliforms and E.coli \r \r \r Whether the amount of rainfall affects these levels. \r \r \r If faecal pollution is present, to determine the possible point sources of the pollution \r \r \r To devise a method that needs no assistance from a laboratory, and could be done in a home environment at low cost. \r \r \r \r Procedures \r Colilert-18, (the reagent) contains nutrients which react to faecal-coliforms and E.coli in the sample. It causes samples to change colour when contamination is present. A dilution method (used by the Kowie Catchment Campaign) was used to test the severity of the contamination. The dilution levels were as follows: 1, 1/10, 1/100 and 1/1000. A control test was also performed. One Colilert capsule was divided among the five samples, which were incubated in a household stove at 37ºC for 18 hours. A sample was collected every four days and after heavy rainfall. \r The results were rated on a severity scale of 0-4, where a two was considered unsafe for recreational activity. If the undiluted sample remained clear, it was ra ted 0, if all the samples changed colour, it was rated as a four. The same rating system was used when fluorescing samples to test for E.coli. The daily rainfall level was compared to the levels of faecal-coliforms and E.coli. \r Conclusion \r As it has high levels of faecal coliforms and E.coli, the Nahoon River is not safe for recreational activity on a daily basis. \r Heavy rainfall causes the levels of E.coli and faecal coliforms to rise. \r The major source of the contamination is a stream entering the river from a newly developed settlement, and not a leaking sewer. \r This experiment has developed cost-effective home environment testing method which could be used in researching other rivers, marine environments, recreational waters and even drinking water by community researc