Target shielding

Forklift energy sources (e.g., hot brake pads, battery failure, electrical system ilure, collision, etc.) Hydraulic oil, diesel fuel, gasoline, propane fuel Irradiated isotope production target shielding casks are not combustible but heat of a tire could pressurize the target Some forklifts in HCF are electric so no fiiels present... 

Target shielding (sputtering) Shielding of the target to prevent the establishment of a plasma between the shield and the target. 

The concrete block walls of the cell housing the generator tube and associated components are 1.7 meters thick. The facility also includes a Kaman Nuclear dual-axis rotator assembly for simultaneous transfer and irradiation of reference and unknown sample, and a dual Na iodide (Nal) scintillation detector system designed for simultaneous counting of activated samples. Automatic transfer of samples between load station to the rotator assembly in front of the target, and back to the count station, is accomplished pneumatically by means of two 1.2cm (i.d.) polyethylene tubes which loop down at both ends of the system and pass underneath the concrete shielding thru a pipe duct. Total one-way traverse distance for the samples is approx 9 meters. In performing quantitative analysis for a particular element by neutron activation, the usual approach is to compare the count rates of an unknown sample with that of a reference standard of known compn irradiated under identical conditions... 

Radiation exposure can be reduced by placing the radiation source or the potential target behind a shield that captures the radiation. During exposure to X rays for dental imaging, the patient wears a lead-lined pad, because X rays are absorbed more effectively by lead than by any other material. A lead shield a few millimeters thick is sufficient to stop X rays. 

Adjustable Workbench (PAW) instrument assembly. The SH shown in Figs. 3.15 and 3.16 contains the electromechanical transducer (mounted in the center), the main and reference Co/Rh sources, multilayered radiation shields, detectors and their preamplifiers and main (linear) amplifiers, and a contact plate and sensor. The contact plate and contact sensor are used in conjunction with the IDD to apply a small preload when it places the SH holding it firmly against the target. The electronics board contains power supplies/conditioners, the dedicated CPU, different kinds of memory, firmware, and associated circuitry for instrument control and data processing. The SH of the miniaturized Mossbauer spectrometer MIMOS II has the dimensions (5 x 5.5 x 9.5) cm and weighs only ca. 400 g. Both 14.4 keV y-rays and 6.4 keV Fe X-rays are detected simultaneously by four Si-PIN diodes. The mass of the electronics board is about 90 g [36],... 

Shielded polyplexes with improved blood circulating properties are interesting tools for systemic cancer therapy (see Sect. 4.2). Nanoparticles can take advantage of the enhanced permeability and retention (EPR effect) [89] for passive tumor targeting. The EPR effect is based on the leakiness of tumor vasculature, due to neovascularization in growing tumors, combined with an inadequate lymphatic drainage. Nanoparticles with an elongated plasma circulation time can extravasate and passively accumulate at the tumor site. 

A highly stable and shielded polyplex should circulate in the blood stream without undesired interactions until it reaches the target cell. At that location, specific interactions with the cell surface should trigger intracellular uptake. While lipid membrane interaction is undesired at the cell surface, it should happen subsequently within the endosomal vesicle and mediate polyplex delivery into the cytosol. During or after intracellular transport to the site of action, the polyplex stability should be weakened to an extent that the nucleic acid is accessible to exert its function. 

Various researchers have applied the receptor-targeted strategy in pharmacological models for tumor-targeted delivery of pDNA expressing tumor necrosis factor alpha (TNFa). For example, Tf- or Tf-PEG-shielded PEI polyplexes have been used... 

Tf-containing PEG-shielded polyplexes have also been applied for systemic tumor-targeted delivery of siRNA [106-108]. Systemic treatment of Neuro 2A tumorbearing mice using Tf-PEG-shielded crosslinked oligoethylenimines for delivery of siRNA against Ras-related nuclear protein (Ran) led to >80% reduced Ran protein expression, associated with tumor apoptosis and reduced tumor growth [108]. 

Kircheis R, Wightman L, Schreiber A, Robitza B, Rossler V, Kursa M, Wagner E (2001) Polyethylenimine/DNA complexes shielded by transferrin target gene expression to tumors after systemic application. Gene Ther 8 28 10... 

Shields, L.M. and P.V. Wells. 1963. Recovery of vegetation on atomic target areas at the Nevada test site. Pages 307-310 in V. Schultz and A.W. Klement, Jr. (eds.). Radioecology. Reinhold, New York. 

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