Primary implantation

A crucial parameter in implanted source preparation is the total implant dose. For on-line work the flux of implant ions is very low as we are far from any stable beam. Even a flux of 106 ions s "1 gives only 1011 ions/day, well below the limiting concentration of order 0.1 atomic percent if implantation is at 50 KeV or above. A valuable feature of OLNO is that a sequence of isotopes may be simultaneously studied as the primary implant decays towards the stability line. This frequently makes accessible isotopes of elements which do not readily form ion beams. 

The primary implanted atoms may propagate much further into the crystal by following the direction of a channel . The host atoms, forming the walls of the channel, give rise, due to their potential distribution, to a focusing effect along the centre of the channel. The consequence is that channeled atoms are found up to 10 times further inside a crystal than random ones ... 

Goldenberg I, Vyas AK, Hall WJ, et al. Risk stratification for primary implantation of a cardioverter-defibrillator inpatients with ischemic left ventricular dysfunction. J Am Coll Cardiol 2008 51(3) 288-96. 

Cardiac Resynchronization for Primary Implantation in Patients with a Conventional Indication for Antibradycardia Pacing... 

Before the era of primary implantation, ICD therapy generally used to fit in the cost-effective range of 20,000- 40,000 (136,210-213). MushUn assessed incremental cost-effectiveness of ICD implant in the MADIT trial (214). After 4 years, ICD implants were associated with an incremental benefit of 0.8 years. Based on this survival benefit, the authors estimated that ICD cost was 22,800 for the 181 patients who received a transvenous device. The cost per life year saved for ICDs in the AVID trial was > 114,917. The reason for this extraordinarily high cost is, in part due to the short-term follow-up, and the short (2.9-month) survival advantage for the ICD group despite a 37% reduction in mortality. 

Parylene s use in the medical field is linked to electronics. Certain pacemaker manufacturers use it as a protective conformal coating on pacemaker circuitry (69). The coated circuitry is sealed in a metal can, so that the parylene coating serves only as a backup should the primary barrier leak. There is also interest in its use as an electrode insulation in the fabrication of miniature electrodes for long-term implantation to record or to stimulate neurons in the central or peripheral nervous system, as the "front end" of experimental neural prostheses (70). One report describes the 3-yr survival of functioning parylene-coated electrodes in the brain of a monkey (71). 

The consistent improvement in rate of protein deposition observed in growing mminants indicates that anaboHc steroid implants exert their primary influence through altering protein metaboHsm. There are lesser effects on Hpid metaboHsm. 

The primary sources of contamination in ion implantation come from metal atoms that may be etched off reactor fixtures, such as reactor wads, wafer holder, cHps, and so on. The pump oils used by the vacuum pumps may be a source of hydrocarbon contamination. The dopant sources themselves are not a significant source of contamination because unwanted ions are separated out from the beam during beam analysis. 

The physical techniques used in IC analysis all employ some type of primary analytical beam to irradiate a substrate and interact with the substrate s physical or chemical properties, producing a secondary effect that is measured and interpreted. The three most commonly used analytical beams are electron, ion, and photon x-ray beams. Each combination of primary irradiation and secondary effect defines a specific analytical technique. The IC substrate properties that are most frequendy analyzed include size, elemental and compositional identification, topology, morphology, lateral and depth resolution of surface features or implantation profiles, and film thickness and conformance. A summary of commonly used analytical techniques for VLSI technology can be found in Table 3. 

Radiation Damage. It has been known for many years that bombardment of a crystal with energetic (keV to MeV) heavy ions produces regions of lattice disorder. An implanted ion entering a soHd with an initial kinetic energy of 100 keV comes to rest in the time scale of about 10 due to both electronic and nuclear coUisions. As an ion slows down and comes to rest in a crystal, it makes a number of coUisions with the lattice atoms. In these coUisions, sufficient energy may be transferred from the ion to displace an atom from its lattice site. Lattice atoms which are displaced by an incident ion are caUed primary knock-on atoms (PKA). A PKA can in turn displace other atoms, secondary knock-ons, etc. This process creates a cascade of atomic coUisions and is coUectively referred to as the coUision, or displacement, cascade. The disorder can be directiy observed by techniques sensitive to lattice stmcture, such as electron-transmission microscopy, MeV-particle channeling, and electron diffraction. 

Valve Problems. The primary solution to valve problems has been implantable replacement valves. The introduction of these devices necessitates open-heart surgery. There are two types of valves available tissue (porcine and bovine) and mechanical. The disadvantage of tissue valves is that these have a limited life of about seven years before they calcify, stiffen, and have to be replaced. The mechanical valves can last a lifetime, but require anticoagulant therapy. In some patients, anticoagulants may not be feasible or may be contraindicated. Of the valves which require replacement, 99% are mitral and aortic valves. The valves on the left side of the heart are under much greater pressure because the left ventricle is pumping blood out to the entire body, instead of only to the lungs. Occasionally, two valves are replaced in the same procedure. 

Impla.nta.ble Ports. The safest method of accessing the vascular system is by means of a vascular access device (VAD) or port. Older VAD designs protmded through the skin. The totally implanted ports are designed for convenience, near absence of infection, and ease of implantation. Ports allow dmgs and fluids to be deUvered directiy into the bloodstream without repeated insertion of needles into a vein. The primary recipients of totally implanted ports are patients receiving chemotherapy, bolus infusions of vesicants, parenteral nutrition, antibiotics, analgesics, and acquired immune disease syndrome (AIDS) medications. 

The primary advantages of implantable ports are no maintenance between uses other than periodic flushing with heparinized saline every 28 days to ensure patency, lower incidence of clotting and thrombosis, no dressing changes, insignificant infection incidence, unobtmsive cosmetic appearance, and no restriction on physical activity. 

The bombardment of a sample with a dose of high energetic primary ions (1 to 20 keV) results in the destruction of the initial surface and near-surface regions (Sect. 3.1.1). If the primary ion dose is higher than 10 ions mm the assumption of an initial, intact surface is no longer true. A sputter equilibrium is reached at a depth greater than the implantation depth of the primary ions. The permanent bombardment of the sample with primary ions leads to several sputter effects more or less present on any sputtered surface, irrespective of the instrumental method (AES, SIMS, GDOES. ..). 

Implantation of Primary Ions. The primary ions are implanted in the sample and thereby influence the chemical constitution. For energies in the 20 keV range the implantation depth is approximately 30 nm. The sputter yield, i. e. the ratio of secondary to primary particles (not only ions), is energy-dependent and has a maximum in the 10 keV range. 

Fig. 3.26. Depth profiles of P implantations in Si. Primary ions Cs" primary energy 14.5 keV.

Hormonal contraceptives belong to the most widely prescribed and most efficacious drugs that have a profound impact on western societies since their inauguration in the 1960s. In women, oral hormonal contraceptives are used to prevent fertilization or implantation in cases of unplanned pregnancies. Apart from these primary objectives, there are significant additional medical benefits contributing to a substantial improvement of reproductive health in women. 

The rate of in vivo biodegradation of subcutaneous implanted films was very high for chitin compared with that for deacetylated chitin. No tissue reaction was foimd with highly deacetylated chitosans, although they contained abundant primary amino groups [240]. 

Although suppression of FSH and LH is the primary mechanism by which combined oral contraceptives prevent ovulation, there are other mechanisms by which these hormones work to prevent pregnancy. Other mechanisms include reduced penetration of the egg by sperm, reduced implantation of fertilized eggs, thickening of cervical mucus to prevent sperm penetration into the upper genital tract, and slowed tubal motility, which may delay transport of sperm.1 Thus, in... 

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