Role of cross-links in bundle formation, phase separation and gelation of long filaments

We predict the thermodynamic and structural behavior of solutions of long cross-linked filaments. We find that at the mean field level, the entropy of self-assembled junctions induces an effective attraction between the filaments that can result in a phase separation into a connected network, in equilibrium with a dilute phase. A connected network can also be formed in a non-thermodynamic transition upon increase of the chain, or cross link density, or with decreasing temperature. For rigid rods, at low temperatures, we predict a transition from an isotropic network, to anisotropic bundles of rods tightly bound by cross links, that is triggered by the interplay between the configurational entropy of the cross-link distribution among the rods, and the rotational and translational entropy of the rods.Comment: typos and graphics corrected; 6 pages 1 figur

Inclusions induced phase separation in mixed lipid film

The effect of rigid inclusions on the phase behavior of a film containing a mixture of lipid molecules is investigated. In the proposed model, the inclusion-induced deformation of the film, and the resulting energy cost are strongly dependent upon the spontaneous curvature of the mixed film. The spontaneous curvature is in turn strongly influenced by the composition of film. This coupling between the film composition and the energy per inclusion leads to a lateral modulation of the composition, which follows the local curvature of the membrane. In particular, it is shown that the inclusion may induce a global phase separation in a film which would otherwise be homogeneously mixed. The mixed film is then composed of patches of different average composition, separated by the inclusions. This process may be of relevance to explain some aspects of lipid-protein association in biological membranes.Comment: 19 pages, 5 figure

Elastic Interactions of Cells

Biological cells in soft materials can be modeled as anisotropic force contraction dipoles. The corresponding elastic interaction potentials are long-ranged ($\sim 1/r^3$ with distance $r$) and depend sensitively on elastic constants, geometry and cellular orientations. On elastic substrates, the elastic interaction is similar to that of electric quadrupoles in two dimensions and for dense systems leads to aggregation with herringbone order on a cellular scale. Free and clamped surfaces of samples of finite size introduce attractive and repulsive corrections, respectively, which vary on the macroscopic scale. Our theory predicts cell reorientation on stretched elastic substrates.Comment: Revtex, 6 pages, 2 Postscript files included, to appear in Phys. Rev. Let

Sumber Daya Manusia Pendidikan Dalam Menghadapi Era Industri 4.0.

Indonesia is a developing country that is facing the Industrial Revolution 4.0 Era. Many things must be changed in a country if the country wants to become a developed country. This also applies to Indonesia, especially when the level of competition is getting tougher in various sectors of our lives. From the various changes that must be made, improvement of Human Resources (HR) is one of the priorities that must be considered, especially HR in the field of Education. The worldwide Industrial Revolution 4.0 has changed the mindset and the application of educational innovation in all fields of educational programs. Therefore, all stakeholders, implementers of education in Indonesia must be able to take advantage of Information Technology advancement in developing appropriate and religious education models to produce educational human resources that are in accordance with the Industrial 4.0 Erain order to realize Indonesian people who understand Science and Technology, have Faith and Taqwa and ready to face the times. In terms of the availability of Human Resources in the field of Education to face the Industry 4.0 Era, the role of Higher Education should not be ignored, because all activities, professions, and our social life are directly related to the quality of existing Higher Education graduates. Thus, this paper is focused on how to realize Human Resources in the field of Educationin Facing the Industry 4.0 Era

Protein gradients in single cells induced by their coupling to "morphogen"-like diffusion

One of the many ways cells transmit information within their volume is through steady spatial gradients of different proteins. However, the mechanism through which proteins without any sources or sinks form such single-cell gradients is not yet fully understood. One of the models for such gradient formation, based on differential diffusion, is limited to proteins with large ratios of their diffusion constants or to specific protein-large molecule interactions. We introduce a novel mechanism for gradient formation via the coupling of the proteins within a single cell with a molecule, that we call a "pronogen", whose action is similar to that of morphogens in multi-cell assemblies, the pronogen is produced with a fixed flux at one side of the cell. This coupling results in an effectively non-linear diffusion degradation model for the pronogen dynamics within the cell, which leads to a steady-state gradient of the protein concentration. We use a stability analysis to show that these gradients are linearly stable with respect to perturbations.Comment: To appear in J. Chem. Phy

EKSPLORASI FUNGI MIKORIZA ARBUSKULA PADA PERKEBUNAN KELAPA SAWIT PT. LEMBAH BHAKTI DI RAWA SINGKIL DENGAN KULTUR TRAPPING

RINGKASANFungi mikoriza arbuskula (FMA) adalah kelompok fungi yang bersimbiosis mutualisme dengan akar tanaman, FMA dapat berasosiasi dengan 90% jenis tanaman dikotiledon, monokotiledon. Penelitian ini bertujuan untuk mengetahui pengaruh umur kelapa sawit dan jenis media pembawa pada kultur trapping terhadap populasi dan keanekaragaman FMA pada rizosfer kelapa sawit di PT. Lembah Bhakti pada Rawa Singkil. Penelitian ini mengunakan metode deskriftif kuantatif. Pengambilan sampel dilakukan pada Perkebunan Kelapa Sawit PT. Lembah Bhakti Kecamatan Singkil Utara. Aceh Singkil. Sampel yang diambil berupa tanah dan akar kelapa sawit dirizosfir berbagai umur kelapa sawit ( 5, 10 dan 15 tahun) pada kedalaman 0-20. Kultur trapping dengan mengunakan media pembawa zeolit, pasir, dan biochar dilakukan berdasarkan metode Bundreett et. al (1996). Pengamatan jumlah spora mengunakan metode tuang saring basah (Pacioni, 1992 dalam Brundreet et al(1996)dan dilanjutkan dengan teknik sentrifugasi (Brundrett et al., 1996). Identifikasi spora FMA dilakukan mengacu pada Manual for the Identification of Mychorrhiza Fungi (Schenk and Perez,1990). Pengamatan kolonisasi akar oleh FMA dengan metode dari Kormanik dan Grew (1982)Hasil penelitian menunjukkan kepadatan spora tertinggi didapatkan pada umur rizosf ks umur 5 tahun ( 65 spora per 50g tanah) sedangkan kolonisasi akar tertinggi didapatkan pada umur 10 tahun ( 39,6 %). zeolit merupakan media pembawa terbaik dalam kultur trapping yg ditunjukkan oleh lebih tingginya kepadatan spora maupun kolonisasi akar.Terdapat dua genus yang ditemukan pada rizosfir kelapa sawit PT. Lembah Bhakti yaitu Glomus dan Acaulospora. glomus merupakan genus yang dominan dan dari semua spesies yang didapat glomus sp1 merupakan spesies yang lebih dijumpai dibandingkan spesies lainnya