EFFISIENSI INHIBISI INHIBITOR EKSTRAK DAUN TEH (Camelia sinensis) TERHADAP BAJA St-37 DALAM MEDIUM ASAM DAN GARAM

<p class="51JUDULABSTRAK">Telah dilakukan penelitian untuk mengendalikan laju korosi baja St-37 dalam medium asam klorida dan natrium klorida menggunakan inhibitor ekstrak daun teh <em>(Camelia sinensis)</em>. Metode weight loss dan metode potensiodinamik untuk menentukan laju korosi, dalam medium HCl 3 % dan NaCl 3 %, dengan konsentrasi inhibitor yang ditambahkan bervariasi mulai dari 1 % hingga 10 % dengan perendaman selama empat hari. Hasil penelitian menunjukan bahwa laju korosi berkurang dengan meningkatnya konsentrasi inhibitor yang ditambahkan, Peningkatan konsentrasi inhibitor diikuti juga dengan meningkatnya nilai effisiensin inhibisinya. Nilai efisiensi terbesar 86,3 % dengan penambahan konsentrasi inhibitor 10 % untuk medium korosif HCl dan dengan konsentrasi yang sama untuk NaCl mencapai 92,0%. Analisis morfologi permukaan dengan foto optik memperlihatkan permukaan baja dengan penambahan ekstrak daun teh mengalami korosi lebih sedikit dibandingkan dengan tanpa inibitor. Hal ini menunjukan bahwa inhibitor ekstrak daun teh sangat efisien untuk mengendalikan laju korosi dalam medium korosif HCl dan NaCl.</p><p class="52ISIABSTRAKCxSpMiddle"> </p><p class="52ISIABSTRAKCxSpMiddle">A research to control corrosion rate of St-37 steel in acid chloride and sodium chloride medium using tea leaf (Camellia sinensis) extract inhibitor has been done. The method used is potentiodynamic to see the value of the corrosion current and weight loss method for corrosion rate.. Corrosive medium used were HCl 3% and NaCl 3%. The concentration of the extract used range from 1%-10% and the immersion time is four days. The results showed that the corrosion rate was greatest in the corrosive medium without addition of inhibitors, whereas the corrosion rate decreases with the addition of inhibitors, it is also evident from the results of the Tafel plot shows I_corimpairment. The greater the concentration of inhibitor that is used the lower the corrosion rate. Greatest efficiency values both for medium corrosive obtained at inhibitor concentrations of 10%, 86,3% in HCl and 92% in NaCl. This shows that tea leaves extract inhibitor is very efficient in controlling the rate of corrosion in HCl and NaCl medium. From the optical photograph analysed on the surface morphology of St-37 steel showed that the addition of tea leaf extract suffered less corrosion.</p>

A new collagen solution with high concentration and collagen native structure perfectly preserved

Optical photograph of collagen solutions in different solvents.

Wave dynamics and star formation in Taurus

The mechanism underlying the formation of cores and larger scale structures in molecular clouds must play a fundamental role in the physics of star formation since young stellar objects are usually found within or very near cores (Myers et al 1987, Beichman et al 1986). The Taurus cloud is an ideal object to study in this regard because of its proximity (160 pc), and because only low mass star formation is presently occurring there. Barnard's (1927) beautiful optical photograph of the region reveals that the obscuring gas and dust has filamentary structure that is comparable to the size of the cloud complex (several 10's of pc). This structure is clearly seen in CO maps of the region as well (eg. Duvert et al 1986) where it is apparent that structure on much larger size scales than cores is common. In addition to the filamentary structure one also observes that there are small dark clouds present such as L1489, L1495, etc.

Wave dynamics and star formation in Taurus

The mechanism underlying the formation of cores and larger scale structures in molecular clouds must play a fundamental role in the physics of star formation since young stellar objects are usually found within or very near cores (Myers et al 1987, Beichman et al 1986). The Taurus cloud is an ideal object to study in this regard because of its proximity (160 pc), and because only low mass star formation is presently occurring there. Barnard's (1927) beautiful optical photograph of the region reveals that the obscuring gas and dust has filamentary structure that is comparable to the size of the cloud complex (several 10's of pc). This structure is clearly seen in CO maps of the region as well (eg. Duvert et al 1986) where it is apparent that structure on much larger size scales than cores is common. In addition to the filamentary structure one also observes that there are small dark clouds present such as L1489, L1495, etc.

M51’s Spiral Structure

The M51 system (NGC 5194/5195) provides an excellent problem both in spiral structure and in galaxy interactions. We present an analytic study of a computer experiment on the excitation mechanisms for M51’s spiral arms and whether or not a halo is important for these mechanisms. This work extends previous numerical studies of the M51 system by including self-gravitation in a two component disk: ’gas’ and ’stars’, and a dark halo. The analytic study provides two new observational constraints: the time (≈ 70 — 84 million years ago) and position angle of perigalacticon (300°). By using these constraints and a simple conic approximation, the search for the companion’s possible orbit is greatly simplified. This requires fewer N-body simulations than a fully self-gravitating orbit search. Fig. 1 shows the dust lane spiral pattern of M51 overlaid on an optical photograph. The analytically determined direction of perigalacticon is indicated with a line.