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Biomedical subjects

Q Geng

Publications and source records attributed to Q Geng.

8 recordsLinked to original sources
PubMed2006

Temperature limit values for touching cold surfaces with the fingertip.

OBJECTIVES: At the request of the European Commission and in the framework of the European Machinery Directive, research was performed in five different laboratories to develop specifications for surface temperature limit values for the short-term accidental touching of the fingertip with cold surfaces. METHODS: Data were collected in four laboratories with a total of 20 males and 20 females performing a grand total of 1655 exposures. Each touched polished blocks of aluminium, stainless steel, nylon-6 and wood using the distal phalanx of the index finger with a contact force of 1.0, 2.9 and 9.8 N, at surface temperatures from +2 to -40 degrees C for a maximum duration of 120 s. Conditions were selected in order to elicit varying rates of skin cooling upon contact. Contact temperature (TC) of the fingertip was measured over time using a T-type thermocouple. RESULTS: A database obtained from the experiments was collated and analysed to characterize fingertip contact cooling across a range of materials and surface temperatures. The database was subsequently used to develop a predictive model to describe the contact duration required for skin contact temperature to reach the physiological criteria of onset of pain (15 degrees C), onset of numbness (7 degrees C) and onset of frostbite risk (0 degrees C). CONCLUSIONS: The data reflect the strong link between the risk of skin damage and the thermal properties of the material touched. For aluminium and steel, skin temperatures of 0 degrees C occurs within 2-6 s at surface temperatures of -15 degrees C. For non-metallic surfaces, onset of numbness occurs within 15-65 s of contact at -35 degrees C and onset of cold pain occurs within 5 s of contact at -20 degrees C. The predictive model subsequently developed was a non-linear exponential expression also reflecting the effects of material thermal properties and initial temperature. This model provides information for the protection of workers against the risk of cold injury by establishing the temperature limits of cold touchable surfaces for a broad range of materials, and it is now proposed as guidance values in a new international standard.

Adolescent↗
PubMed2002

Temperature limit values for gripping cold surfaces.

OBJECTIVES: At the request of the European Commission and in the framework of the European Machinery Directive, research was conducted jointly in five different laboratories to develop specifications for surface temperature limit values for the gripping and handling of cold items. METHODS: Four hundred and fourteen experiments were run where male and female subjects were invited to grip for up to 20 min cold bars of different contact coefficients, i.e. polished wood, nylon, stone, steel and aluminium. The air temperature and the bars' initial surface temperatures ranged between 0 and -30 degrees C for the various experiments. While gripping the bars, either only the hand or the whole body was exposed to cold. RESULTS: The data were used to develop a prediction formula and a graph of the surface temperature limit values in order for the skin contact temperature not to reach <15 degrees C. This duration is shown to offer a significant degree of safety with respect to the minimal surface temperature spontaneously tolerated by the subjects. CONCLUSIONS: Experiments and modelling must be pursued to extend these data to other conditions of exposure.

Adult↗
PubMed2000

[Mature time demarcation of human immature myocardium].

OBJECTIVE: To study the mature time demarcation of human immature myocardium. METHODS: The morpho-ultrastructure, calcium metabolism, energy metabolism and oxygen free radicals metabolism of myocardium of children with ventricular septal defect without pulmonary hypertension or any clinical symptoms were studied at different ages. RESULTS: The immature myocardium possessed its own structure and functional characteristics. Before viripotent period, the age-related myocardial changes developed progressively to mature and almost approached to mature levels at 6-9 years old. The indices of immature myocardium developing to mature levels were inconsistent. CONCLUSION: The structure and function of human immature myocardium approaches to mature levels at 6-9 years old.

Adolescent↗
PubMed1997

Tactile sensitivity of gloved hands in the cold operation.

In this study, tactile sensitivity of gloved hand in the cold operation has been investigated. The relations among physical properties of protective gloves and hand tactile sensitivity and cold protection were also analysed both objectively and subjectively. Subjects with various gloves participated in the experimental study during cold exposure at different ambient temperatures of -12 degrees C and -25 degrees C. Tactual performance was measured using an identification task with various sizes of objects over the percentage of misjudgment. Forearm, hand and finger skin temperatures were also recorded throughout. The experimental data were analysed using analysis of variance (ANOVA) model and the Tukey's multiple range test. The results obtained indicated that the tactual performance was affected both by gloves and by hands/fingers cooling. Effect of object size on the tactile discrimination was significant and the misjudgment increased when similar sizes of objects were identified, especially at -25 degrees C.

Adult↗
PubMed1996

Application of a newly developed 3-D deformation measurement system to prosthetic dentistry.

A new system for measuring three-dimensional deformation has been developed. The main components of the system are a fixed TV camera and vertically scanning projectors. The advantages of the system are: (1) since there is no mechanical contact between the object and the sensing unit, hardness and form of the object do not have to be considered; (2) the system does not need any precise geometry except for the reproducibility of the vertical scanning stage; (3) the time required for one measurements is extremely short; and (4) the system is not expensive. From the basic experiments for testing accuracy, this system has about +/- 30 microns range deviation against 1000 microns deformation of the object. The system has been applied to investigate the influence of various impression procedures for a removable partial denture on the displacement of the simulated soft mucosal tissue. It is revealed that deformation forms are expressed precisely. Our results suggest that this measurement system is quite useful for research in dentistry and that it could be widely applied.

Biomechanical Phenomena↗
PubMed1993

[Influence of various impression procedures for removable partial denture on displacement of soft mucosal tissue].

In the impression-taking procedure for the distal extension removable partial denture, the pressure produced at the interface of the soft mucosal tissue and the impression material is the most important factor for the stability of the saddle under functional load. However, a review of the literature revealed little information about the displacement of the soft tissue caused by the impression pressure. In the present study, to investigate the influence of various impression procedures on the magnitude of the soft tissue displacement more precisely, a new three-dimensional deformation measurement system was devised. Compared to the previous studies, the greatest advantage of the system is that the hardened impression material can be surveyed directly without substituting a dental stone. It was found that, in the investigation using a partially edentulous simulated model, the amount of the subsidence in the soft tissue was increased as the thickness of the spacer of the impression tray was reduced or the seating speed of the tray was fast. Especially in the buccal area, a large amount of vertical displacement was present compared to the midridge and lingual area. Thus it was suggested that many factors are associated with the form of soft tissue under impression loading.

Computer Simulation↗