Kloning Manusia

In the last few years, very rapid progress in the cloning technology and its development towards human cloning has become a hotly-debated issue. Cloning, which is the process of formation of a number of individuals with the same genetic structure, can be done by means of embryo-splitting method and nuclear transfer. Human cloning through the nuclear transfer method is directed towards two purposes, i.e. reproduction and therapy. The relatively new transgenic technology can be combined with the cloning technique to produce clones with new genes. However, pros and cons arise concerning the development of research on human cloning, particularly cloning for reproductive purposes. Therefore, there is need for a moratorium period before human cloning can be performed in order that solutions for all kinds of problems related to safety and ethics can be found

Interaction of Carbene and Olefin Donors with [Cl₂PN]₃: Exploration of a Reductive Pathway toward (PN)₃

The iminophosphine–phosphazene [P^III–P^V] heterocyclic adduct [IPr·PN(PCl₂N)₂] was prepared via reduction of the cyclic phosphazene [Cl₂PN]₃ in the presence of the carbene donor IPr {IPr = [(HCNDipp)₂C:], where Dipp = 2,6-ⁱPr₂C₆H₃}. By contrast, the treatment of [Cl₂PN]₃ with the N-heterocyclic olefin IPrCH₂ yielded the olefin-grafted phosphazene ring [(IPrCH)P(Cl)N(PCl₂N)₂]

Rolling Silver Nanowire Electrodes: Simultaneously Addressing Adhesion, Roughness, and Conductivity

Silver nanowire mesh electrodes represent a possible mass-manufacturable route toward transparent and flexible electrodes for plastic-based electronics such as organic photovoltaics (OPVs), organic light emitting diodes (OLEDs), and others. Here we describe a route that is based upon spray-coated silver nanowire meshes on polyethylene terephthalate (PET) sheets that are treated with a straightforward combination of heat and pressure to generate electrodes that have low sheet resistance, good optical transmission, that are topologically flat, and adhere well to the PET substrate. The silver nanowire meshes were prepared by spray-coating a solution of silver nanowires onto PET, in air at slightly elevated temperatures. The as-prepared silver nanowire electrodes are highly resistive due to the poor contact between the individual silver nanowires. Light pressure applied with a stainless steel rod, rolled over the as-sprayed silver nanowire meshes on PET with a speed of 10 cm s^–1 and a pressure of 50 psi, results in silver nanowire mesh arrays with sheet resistances of less than 20 Ω/□. Bending of these rolled nanowire meshes on PET with different radii of curvature, from 50 to 0.625 mm, showed no degradation of the conductivity of the electrodes, as shown by the constant sheet resistance before and after bending. Repeated bending (100 times) around a rod with a radius of curvature of 1 mm also showed no increase in the sheet resistance, demonstrating good adherence and no signs of delamination of the nanowire mesh array. The diffuse and direct transmittance of the silver nanowires (both rolled and as-sprayed) was measured for wavelengths from 350 to 1200 nm, and the diffuse transmission was similar to that of the PET substrate; the direct transmission decreases by about 7–8%. The silver nanowires were then incorporated into OPV devices with the following architecture: transparent electrode/PEDOT:PSS/P3HT:PC₆₁BM/LiF/Al. While slightly lower in efficiency than the standard indium tin oxide substrate (ITO), the rolled silver nanowire electrodes had a very good device yield, showing that short circuits resulting from the silver nanowire electrodes can be successfully avoided by this rolling approach

Stable Complexes of Parent Digermene: An Inorganic Analogue of Ethylene

The elusive parent inorganic ethylene H₂GeGeH₂ has been isolated in the form of a stable complex for the first time via donor–acceptor coordination with suitable Lewis base/acid combinations (LB·H₂Ge-GeH₂·LA; LB = N-heterocyclic carbene or N-heterocyclic olefin; LA = W­(CO)₅). The nature of the bonding in these species was investigated by density functional theory calculations and revealed the presence of polarized Ge–Ge covalent σ-bonds within the H₂Ge–GeH₂ arrays and dative Ge–C interactions between the digermene and the carbon-based Lewis bases

Expanding the Steric Coverage Offered by Bis(amidosilyl) Chelates: Isolation of Low-Coordinate <i>N</i>-Heterocyclic Germylene Complexes

The synthesis and coordination chemistry of a series of dianionic bis­(amido)­silyl and bis­(amido)­disilyl, [NSiN] and [NSiSiN], chelates with N-bound aryl or sterically modified triarylsilyl (SiAr₃) groups is reported. In order to provide a consistent comparison of the steric coverage afforded by each ligand construct, various two-coordinate <i>N</i>-heterocyclic germylene complexes featuring each ligand set were prepared and oxidative S-atom transfer chemistry was explored. In the cases where clean oxidation transpired, sulfido-bridged centrosymmetric germanium­(IV) dimers of the general form [LGe­(μ-S)]₂ (L = bis­(amidosilyl) ligands) were obtained in lieu of the target monomeric germanethiones with discrete GeS double bonds. These results indicate that the reported chelates possess sufficient conformational flexibility to allow for the dimerization of LGeS units to occur. Notably, the new triarylsilyl groups (4-RC₆H₄)₃Si (R = ^<i>t</i>Bu and ^<i>i</i>Pr) still offer considerably expanded degrees of steric coverage relative to the parent congener, SiPh_3, and thus the use of substituted triarylsilyl groups within ligand design strategies should be a generally useful concept in advancing low-coordination main group and transition-metal chemistry