Kriteria Visibilitas Hilal Rukyatul Hilal Indonesia (Rhi) (Konsep, Kriteria, dan Implementasi)

Telah dilaksanakan observasi hilal dan hilal tua selama periode Zulhijjah 1427–Zulhijjah 1430 H (Januari 2007–Desember 2009) oleh jejaring titik observasi Rukyatul Hilal Indonesia (RHI) yang merentang dari lintang 5° LU hingga 31° LS, dengan ataupun tanpa bantuan alat bantu optik. Observasi menghasilkan 174 data visibilitas yang terdiri dari 107 visibilitas positif dan 67 visibilitas negatif. Analisis korelasi linier Lag dengan Best Time Bulan menghasilkan definisi baru tentang hilal, yaitu Bulan pasca konjungsi yang memiliki Lag ≤ 24 menit hingga Lag ≤ 40 menit saat Matahari terbenam. Hubungan Best Time dan Lag memenuhi persamaan linear Yallop hanya untuk Lag ≤ 40 menit. Analisis korelasi aD dan DAz dengan metode least–square menghasilkan persamaan kriteria RHI aD ≥ 0,099 DAz2–1,490 DAz + 10,382 yang bentuknya hampir sama dengan kriteria LAPAN, namun sangat berbeda dibanding kriteria Fotheringham–Maunder maupun Bruin. Analisa komparatif menyimpulkan asumsi yang dipergunakan “kriteria” Imkanur Rukyat versi MABIMS dan konsep wujudul hilal tidak terbukti. Sebaliknya, terdapat kesesuaian antara hasil observasi dengan kriteria Odeh

pH-sensitive polyvinylpyrrolidone-acrylic acid hydrogels: Impact of material parameters on swelling and drug release

In this study, we fabricated pH-sensitive polyvinylpyrrolidone/acrylic acid (PVP/AA) hydrogels by a free-radical polymerisation method with variation in the content of monomer, polymer and cross-linking agent. Swelling was performed in USP phosphate buffer solutions of pH 1.2, 5.5, 6.5 and 7.5 with constant ionic strength. Network structure was evaluated by different parameters and FTIR confirmed the formation of cross-linked hydrogels. X-ray crystallography showed molecular dispersion of tramadol HCl. A drug release study was carried out in phosphate buffer solutions of pH 1.2, 5.5 and 7.5 for selected samples. It was observed that swelling and drug release from hydrogels can be modified by changing composition and degree of cross-linking of the hydrogels under investigation. Swelling coefficient was high at higher pH values except for the one containing high PVP content. Drug release increased by increasing the pH of the medium and AA contents in hydrogels while increasing the concentration of cross-linking agent had the opposite effect. Analysis of the drug release mechanism revealed non-Fickian transport of tramadol from the hydrogels

Mesenchymal Stem Cells for Craniofacial Tissue Regeneration: Designing Hydrogel Delivery Vehicles

Craniofacial injuries require a variety of different cell types to repopulate areas of bone, cartilage, tendon, and fat. Mesenchymal stem cells (MSCs) provide a multipotent cell source for tissue engineering of this area, particularly when the cells are delivered via a 3D hydrogel environment. MSC differentiation into cartilage, bone, and fat has been investigated through a variety of techniques, some of which include the use of synthetic hydrogel scaffolds, integration of extracellular matrix components and other natural gel chemistries, microparticle delivery of growth factors, simultaneous mechanical stimulation, and the delivery of microRNA. This review aims to summarize the most recent studies involving the synthesis and application of 3D hydrogels to induce the differentiation of encapsulated MSCs and their subsequent matrix production

Photoregulated hydrazone-based hydrogel formation for biochemically patterning 3D cellular microenvironments

Photodriven click reactions have emerged as versatile tools for biomaterial synthesis that can recapitulate critical spatial and temporal changes of extracellular matrix (ECM) microenvironments in vitro. In this article, we report on the synthesis of poly(ethylene glycol) (PEG) hydrogels using photodriven step-growth polymerization, where one of the reactive functionalities is formed by a photocleavage reaction. Upon photocleavage, an aldehyde functionality is generated that rapidly reacts with hydrazine-functionalized PEGs; the gelation kinetics and final material modulus are distinctly controlled by variations in the light intensity. This light-driven aldehyde generation is further exploited to install biochemical ligands in the hydrazone-based hydrogels with precise spatial control. We expect that user-directed spatial and temporal control over both biophysical and biochemical gel properties through photochemical reactions and photopatterning, respectively, should provide newfound opportunities to probe and understand dynamic cell-matrix interactions