Pengaruh PH Tanah dan Variasi Cacat Gores Lapis Lindung terhadap Kebutuhan Arus Proteksi Sistem Impressed Current Cathodic Protection (ICCP) pada Baja AISI 1045

Korosi merupakan kerusakan atau degradasi pada suatu logam akibat terjadinya reaksi oksidasi antara satu logam dengan banyak zat yang ada dilingkungan sekelilingnya dan membentuk senyawa yang tidak diinginkan terbentuknya. Korosi tidak dapat dicegah namun masih dapat dikendalikan kelajuannya. Salah satu proses pengendalian korosi pada suatu material dapat menggunakan pelapisan/coating dan perlindungan katoda dengan memberikan arus paksa. Pada penelitian yang dilakukan kali ini akan mempelajari mengenai pengaruh dari variasi luas goresan lapis lindung dan pH tanah terhadap kebutuhan arus proteksi pada sistem proteksi katodik arus paksa (ICCP). Luas goresan yang diberikan berbentuk persegi panjang dan lingkaran dengan luasan masing-masing sebesar 10 mm2, 50 mm2, 100 mm2, 150 mm2, 250 mm2, dan 500 mm2. Sedangkan perbedaan pH pada tanah yang digunakan ialah pH 3, pH 7, dan pH 11. Spesimen tanpa goresan dan tanpa lapis lindung digunakan sebagai pembanding. Pada instalasi sistem ICCP, baja AISI 1045 digunakan sebagai katoda dan grafit sebagai anodanya. Sistem menggunakan rectifier yang berguna sebagai penyearah arus. Arus proteksi pada ICCP diatur sedemikian rupa hingga nilai beda potensial dapat mencapai -850 mV terhadap elektroda referensi Cu/CuSO4. Pengukuran arus proteksi pada sistem ICCP dilakukan selama 7 hari dengan pengambilan data setiap harinya. Setelah didapatkan pengukuran dari nilai arus proteksi, didapatkan hasil bahwa nilai arus proteksi terbesar pada luas goresan berbentuk persegi panjang 500 mm2 dengan kondisi tanah yang asam (pH 3) yaitu sebesar 1,696 mA. Sedangkan nilai arus proteksi terkecil pada luas goresan berbentuk lingkaran 10 mm2 dengan kondisi tanah yang basa (pH 11) yaitu sebesar 0,014 mA. Pengaruh dari dua variabel tersebut dihitung menggunakan analisa statistik regresi berganda sehingga mendapatkan persamaan Y = 0,127 + 0,0024 X1 + 0,00031 X2. Dimana nilai X1 sebagai kondisi pH tanah, X2 sebagai luas cacat goresan, dan Y sebagai arus proteksiny

Analisis Keamanan Jembatan Rangka Baja Soekarno – Hatta Malang Ditinjau Dari Aspek Kesehatan, Tegangan Pelat Buhul, Dan Simulasi Kebakaran

Salah satu jalur pergerakan transportasi yang patut menjadi perhatian di Kota Malang adalah Jembatan Rangka Baja Soekarno-Hatta, yang merupakan akses utama pengguna jalan menuju ke area pendidikan dan ke arah kota wisata Batu. Jembatan ini dirasa telah mengalami penurunan kualitas. Dalam penelitian ini, pembahasan dalam difokuskan kepada analisis kesehatan jembatan, kondisi pelat buhul akibat distribusi tegangan yang terjadi, dan kondisi jembatan akibat beban termal. Setelah dilakukan uji Rebound Hammer didapatkan nilai karakteristik sebesar 277,66 kg/cm² dan nilai rebound sebesar 46,79. UPV menunjukkan kualitas beton yang rendah (kecepatan gelombang 1633,6 m/s < 3000 m/s). Pada analisis tegangan pelat buhul, perbedaan antara kondisi ideal dan eksisting sangat jelas. Konsentrasi tegangan pada kondisi ideal tidak melebihi tegangan leleh, sedangkan pada kondisi eksisting konsentrasi tegangan melebihi tegangan leleh. Pada analisis kebakaran di atas jembatan, ketika terjadi kebakaran di tengah bentang, total waktu yang dibutuhkan sampai tegangan batang diagonal mencapai leleh adalah setelah menit ke 18.90 (1134 s) dan mencapai titik putus pada menit ke 19.23 (1154 s). Sedangkan, ketika terjadi kebakaran pada bagian pinggir bentang, waktu yang dibutuhkan jembatan untuk mencapai leleh adalah setelah menit ke 15.81 (949 s), dan pada menit ke 17.95 (1077 s) tegangan batang diagonal mencapai titik putus

Therapeutic potential of endothelial colony‐forming cells in ischemic disease: Strategies to improve their regenerative efficacy

Cardiovascular disease (CVD) comprises a range of major clinical cardiac and circulatory diseases, which produce immense health and economic burdens worldwide. Currently, vascular regenerative surgery represents the most employed therapeutic option to treat ischemic disorders, even though not all the patients are amenable to surgical revascularization. Therefore, more efficient therapeutic approaches are urgently required to promote neovascularization. Therapeutic angiogenesis represents an emerging strategy that aims at reconstructing the damaged vascular network by stimulating local angiogenesis and/or promoting de novo blood vessel formation according to a process known as vasculogenesis. In turn, circulating endothelial colony‐forming cells (ECFCs) represent truly endothelial precursors, which display high clonogenic potential and have the documented ability to originate de novo blood vessels in vivo. Therefore, ECFCs are regarded as the most promising cellular candidate to promote therapeutic angiogenesis in patients suffering from CVD. The current briefly summarizes the available information about the origin and characterization of ECFCs and then widely illustrates the preclinical studies that assessed their regenerative efficacy in a variety of ischemic disorders, including acute myocardial infarction, peripheral artery disease, ischemic brain disease, and retinopathy. Then, we describe the most common pharmacological, genetic, and epigenetic strategies employed to enhance the vasoreparative potential of autologous ECFCs by manipulating crucial pro‐angiogenic signaling pathways, e.g., extracellular‐signal regulated kinase/Akt, phosphoinositide 3‐kinase, and Ca2+ signaling. We conclude by discussing the possibility of targeting circulating ECFCs to rescue their dysfunctional phenotype and promote neovascularization in the presence of CVD

Soft and hard wall in a stochastic reaction diffusion equation

We consider a stochastically perturbed reaction diffusion equation in a bounded interval, with boundary conditions imposing the two stable phases at the endpoints. We investigate the asymptotic behavior of the front separating the two stable phases, as the intensity of the noise vanishes and the size of the interval diverges. In particular, we prove that, in a suitable scaling limit, the front evolves according to a one-dimensional diffusion process with a non-linear drift accounting for a "soft" repulsion from the boundary. We finally show how a "hard" repulsion can be obtained by an extra diffusive scaling.Comment: 33 page

Resonant Inelastic X-Ray Scattering from Valence Excitations in Insulating Copper-Oxides

We report resonant inelastic x-ray measurements of insulating La$_2$CuO$_4$ and Sr$_2$CuO$_2$Cl$_2$ taken with the incident energy tuned near the Cu K absorption edge. We show that the spectra are well described in a shakeup picture in 3rd order perturbation theory which exhibits both incoming and outgoing resonances, and demonstrate how to extract a spectral function from the raw data. We conclude by showing {\bf q}-dependent measurements of the charge transfer gap.Comment: minor notational changes, discussion of anderson impurity model fixed, references added; accepted by PR

SnTox3 Acts in Effector Triggered Susceptibility to Induce Disease on Wheat Carrying the Snn3 Gene

The necrotrophic fungus Stagonospora nodorum produces multiple proteinaceous host-selective toxins (HSTs) which act in effector triggered susceptibility. Here, we report the molecular cloning and functional characterization of the SnTox3-encoding gene, designated SnTox3, as well as the initial characterization of the SnTox3 protein. SnTox3 is a 693 bp intron-free gene with little obvious homology to other known genes. The predicted immature SnTox3 protein is 25.8 kDa in size. A 20 amino acid signal sequence as well as a possible pro sequence are predicted. Six cysteine residues are predicted to form disulfide bonds and are shown to be important for SnTox3 activity. Using heterologous expression in Pichia pastoris and transformation into an avirulent S. nodorum isolate, we show that SnTox3 encodes the SnTox3 protein and that SnTox3 interacts with the wheat susceptibility gene Snn3. In addition, the avirulent S. nodorum isolate transformed with SnTox3 was virulent on host lines expressing the Snn3 gene. SnTox3-disrupted mutants were deficient in the production of SnTox3 and avirulent on the Snn3 differential wheat line BG220. An analysis of genetic diversity revealed that SnTox3 is present in 60.1% of a worldwide collection of 923 isolates and occurs as eleven nucleotide haplotypes resulting in four amino acid haplotypes. The cloning of SnTox3 provides a fundamental tool for the investigation of the S. nodorum-wheat interaction, as well as vital information for the general characterization of necrotroph-plant interactions.This work was supported by USDA-ARS CRIS projects 5442-22000-043-00D and 5442-22000-030-00D

Nucleolar variation in a pigeon pea intergeneric hybrid: evidence for allosyndetic recombination

Cytological study of a hybrid between Cajanus cajan and Atylosia albicans revealed regular bivalent formation and disjunction. Nevertheless, high pollen sterility and low seed set were evident. An examination of pollen mother cells revealed variation in nucleolar number at telophase-I (four to eight) and at telophase-II (zero to four in daughter nuclei), although each genome contained two nucleolar organizers. Variation was also recorded for nucleolar size and distribution at telophase-II. Variation in nucleolar number and distribution are interpreted to have originated from pairing and recombination between nucleolar organizer chromosome(s) of one parental species with the nonnucleolar organizer chromosome(s) of the other. Size variation is attributed to nucleolar dominance. These results explain the high degree of pollen sterility in the hybrid in spite of normal meiosis, and also suggest that the karyotypes of C. cajan and A. albicans have differentiated through structural heterozygosity

Tissue Culture Approaches to Pigeonpea Improvement

Pigeonpea anthers were cultured on different media to develop haploids. MS medium supplemented with 2 mg/L of 2,4 dichlorophenoxy acetic acid (2,4-D) supported the development of callus from Cajanus cajan anthers, while potato starch extract medium promoted the best response from anthers of Atylosia gradifolia and A. volubilis. Such calli failed to differentiate on subculturing on media supplemented with combinations of hormones. Screening for chromosome elimination following intergeneric hybridizations was not successful in haploid formation. Culture conditions for plantlet regeneration from immature embryos of Cajanus have been standardized for further embryo rescue following distant hybridizations. An age-dependent embryo response was evident. Embryos older than 11 days developed into plants on MS or B5 media supplemented with 2,4-D (1 mg/L). The B5 medium was superior to MS for regeneration. Plantlets were also regenerated from explants of cotyledons from mature seeds, leaves and epicotyls of seedlings of Cajanus cultivars and Atylosia species in different media supplemented with hormones [2,4-D, napthalene acetic acid (NAA), benzyl adenine (BA), kinetin and gibberelic acid (GA3)]. Whole cotyledons or their proximal segments were found to be suitable for regeneration

Nucleolar behavior in pollen mother cells in the pigeonpea

Reports on the number of satellite chromosomes in the karyotype of Cajanus cajan are controversial, with the number varying from zero to two. Expression of nucleolar organizer chromosomes during meiosis (prophase-I, telophase-I and telophase-II) is used as an index for the number of nucleolar organizers and conclusive evidence is provided for the presence of two nucleolar organizer chromosomes in Cajanus and also its related species in the genus Atylosia. Nucleolar number in an autotetraplold of Caianus confirmed the evidence from the diploid Cajanus for two nucleolar organizer chromosomes. Variation In the nucleolar size suggests that the two nucleolar organizer chromosomes differ in their activity