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At least 145 records · Page 8Linked to original sources

Evaluation of contrast in duplicated radiographs.

This investigation evaluated changes in the contrast of duplicated radiographs made at different ultraviolet light exposures. Increasing ultraviolet light exposure had different effects on the duplicates of originals of different "background" densities. When correctly exposed, a duplicate radiograph enhanced contrast. When originals had the same contrast but different "background" densities, their duplicates did not have the same contrast. It was not possible to duplicate accurately all the different contrasts measured on an original. It was possible, however, to produce duplicates with all contrasts greater than those of the original.

Copying Processes↗

Sensitometric comparison of unexpired and expired duplicating films used in dentistry.

This investigation compared the sensitometric properties of unexpired and expired duplicating films. The characteristic curve derived for a duplicating film is the negative slope of a solarization curve; that is, it is different in direction to that of a regular x-ray film. An expired duplicating film is slower than an unexpired duplicating film. Unlike a negative working film, which gains fog past its expiration date, a positive working film (for example, a duplicating film) gains contrast past its expiration date. An expired duplicating film has a narrower latitude than that of an unexpired duplicating film for a useful density range. Clinically, a duplicating film can be used years after its expiration date even though there is a change in its speed and contrast.

Copying Processes↗

The vanishing ECG.

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Copying Processes↗

The automation of routine calculations and graphing for alkaline filter elution analysis on a computer-controlled liquid scintillation analyzer.

The data calculations and graphing functions for the widely used alkaline filter elution technique have been completely automated. This saves considerable time and increases both efficiency and accuracy by eliminating human error. The automation was accomplished utilizing Lotus 1-2-3 and Lotus Graphwriter II on a Packard Tri-Carb 1900CA liquid scintillation analyzer containing a built-in pico-XTE computer. A batch file is used to control the overall execution of the process. It copies the data stored by the 1900CA into the Lotus subdirectory and invokes Lotus 1-2-3. A Lotus macro automatically imports the data file, performs the calculations, and prints the results. Graphwriter II is then invoked by the batch file and the charts are composed and graphed. Finally, the instrument operating software for the 1900CA is reentered and sample analysis can be resumed for any unanalyzed samples.

Alkalies↗

The RecE recombination pathway mediates recombination between partially homologous DNA sequences: structural analysis of recombination products.

Escherichia coli generalized recombination, utilizing the RecA RecB recombination pathway, requires large stretches (70-200 bp) of complete DNA sequence homology. In contrast, we have found that the RecE pathway can promote recombination between DNA with only short stretches of homology. A plasmid containing 10 partially homologous direct repeats was linearized by digestion with specific restriction enzymes. After transformation, a RecE+ (sbcA) host was able to circularize the plasmid by recombination between partially homologous direct repeat sequences. Recombination occurred in regions of as little as 6 bp of perfect homology. Recombination was enhanced in the regions adjacent to restriction sites used to linearize the plasmid, consistent with a role of double-strand breaks in promoting recombination. A mechanism is proposed in which the 5' exonuclease, ExoVIII, produces 3' single-stranded ends from the linearized plasmid. These pair with other sequences of partial homology. Partial homologies in the sequences flanking the actual join serve to stabilize this recombination intermediate. Recombination is completed by a process of "copy and join." This recombination mechanism requires less homology to stabilize intermediates than the degree of homology needed for mechanisms involving strand invasion. Its role in nature may be to increase genomic diversity, for example, by enhancing recombination between bacteriophages and regions of the bacterial chromosome.

Base Sequence↗

Characteristics and health impacts of volatile organic compounds in photocopy centers.

This study investigates the indoor air quality of typical photocopy centers in Taiwan to evaluate the human health risk following inhalation exposure. Both personal and area samplings were conducted at seven photocopy centers in the Tainan area from July 2002 to March 2003, which covered both summer and winter seasons in Taiwan. The benzene, toluene, ethylbenzene, xylenes, and styrene (BTEXS) measurements indicated no difference between personal and area samplings (P>0.05) and found that air conditioning improves indoor air quality. The additive factor at each photocopy center was significantly below 1.0, based on the current BTEXS permissible exposure limits in Taiwan. However, the mean benzene and styrene levels in the current study were 138 and 18 times, respectively, higher than those in another study conducted in the United States. Comparison of mass ratios of BTEXS with those of several chamber studies revealed that the photocopier is not the only volatile organic compound (VOC) source in photocopy centers. The lifetime cancer and noncancer risks for workers exposed to VOCs were also assessed. Results show that all seven centers in this study had a lifetime cancer risk exceeding 1x10(-6) (ranging from 2.5x10(-3) to 8.5x10(-5)). Regarding noncancer risk, levels of toluene, ethylbenzene, xylenes, and styrene were below the reference levels in all photocopy centers; however, the hazard indices for all still exceeded 1.0 (range 26.2-1.8) because of the high level of benzene in the photocopy centers.

Adult↗

Portraits of a Y-family DNA polymerase.

Members of the Y-family of DNA polymerases catalyze template-dependent DNA synthesis but share no sequence homology with other known DNA polymerases. Y-family polymerases exhibit high error rates and low processivity when copying normal DNA but are able to synthesize DNA opposite damaged templates. In the past three years, much has been learned about this family of polymerases including determination of more than a dozen crystal structures with various substrates. In this short review, I will summarize the biochemical properties and structural features of Y-family DNA polymerases.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

Genotoxicity evaluation of individuals working with photocopying machines.

Photocopying machines are a common sight in the cities of India. There is ample evidence showing that the components of toners individually or in the form of a complex mixture are genotoxic. Toxic components of the photocopiers are from their emissions, toners and extremely low frequency electromagnetic fields (ELF-EMFs). In the present study micronucleus test (MNT) on buccal epithelial cells, cytokinesis block micronucleus (CBMN) assay and chromosomal aberration analysis on peripheral blood mononuclear cells was performed on 98 workers occupationally involved in photocopying and 90 age and sex matched controls. The results showed a significant increase in the frequency of MN in buccal epithelial cells and peripheral blood lymphocytes, as well as chromosomal aberrations in the exposed as compared to the control subjects.

Adolescent↗

Copying referral letters to patients: the views of patients, patient representatives and doctors.

To discover the views of patients, patient representatives and doctors on copying referral letters to patients. A three-part study: an analysis of 50 GP referral letters against a standard template; 35 patient interviews using a semi-structured questionnaire in outpatient waiting rooms; 3 focus groups of patients, patient representatives and doctors. There was general agreement that copying referral letters to patients could improve information and decision sharing with patients. Copying referral letters could provide an opportunity for patients to correct mistakes, prepare for their appointments and have a personal record that they could keep and show to others. However, there were concerns about letter content, particularly medical terminology, character judgements and "sensitive" patient information. It was also recognised that providing more information to patients could increase patient anxiety. The style and content of some referral letters may need to change. This is particularly relevant where certain types of information included in referral letters could cause distress for patients or influence the time that patients have to wait for their outpatient appointments.

Anxiety↗

Ceramic flask technique for duplicating a complete denture.

The possibilities for use of the duplicate denture are many. The duplicate denture serves as an excellent custom tray for the final working impression. If it is acceptable on the existing denture, the vertical dimension of the duplicate denture can be directly transferred to the articulator. If not acceptable, the vertical dimension can be altered and checked intraorally by adding or removing acrylic resin on the occlusal surface of the teeth. Alterations in esthetics, phonetics, and occlusion can easily be achieved and tested by replacing the original teeth of the duplicate denture with stock acrylic resin teeth. Alterations to the duplicate denture with subsequent patient approval prior to construction of a new prosthesis eliminates many problems associated with new dentures.

Ceramics↗

Computer-printer denture microlabeling system.

This procedure is easy to use and is cost-effective because it uses equipment that exist in any office or institution. The material used, transparency film for use with plain paper copier, is less expensive than either photographic slide film or normal slide films. Moreover, the transparency sheet can be used again for photocopying until the sheet is fully used up. There is no added cost of development of film, or is it necessary to wait for the whole roll of film to be used before the label can be retrieved and used. The background of the label is clear and only the black images of the characters of the label can be clearly seen. The effect of the transparency film, photocopy ink, and adhesive glue is not known. But no adverse effects have been noted. Microlabels have advantages over conventional labels with characters in font size 8 to 12, because more information, such as the full name of the patient, sex, country of origin, and national identification number can be incorporated. With more detailed information, quick identification of a deceased person can be made. Microlabels with a clear background will have minimal esthetic impact on the patient. The disadvantages of the technique is that it may not withstand a fire. In situations where the deceased body is badly burned, the denture and its identification strip may be burned, too. However, this risk can be minimized by placing the strip in the most posterior part of the denture-palatal in the maxillary denture and distal lingual in the mandibular denture. For testing of durability, dentures with the labels were placed in water for up to 4 months. The labels showed no sign of fading or deterioration.

Copying Processes↗