Acute cold stress and mild hypothermia impact on short-term, working memory and attention

The effect of single acute cold water exposure on the cognitive function (short-term, working memory and attention) was examined in 25 male subjects who were exposed to 14 °C cold water (air temperature ~22 °C, rh ~45%) in the semi-recumbent posture (up to the shoulders) until the rectal temperature (T_re) dropped to 35.5 °C. 6 subjects were excluded from the study, because we do not reach a necessary condition to drop their (T_re) to 35.5 °C in 170 minutes during a passive cooling procedure. During the cold exposure rectal (T_re), skin (T_sk) temperatures, heart rate (HR) were measured and cold strain (CSI) was calculated. A cognitive test battery (EFFECTON-COLD) was administrated two times (randomized): as a control measurement (CONTROL) and after the single acute cold water exposure (COLD). After COLD T_re and T_sk significantly decreased (p < 0.05). The average of HR and COLD time was 82.61 ± 4.09 and 93.68 ± 8.66, respectively. The COLD induced CSI resulted as high cold strain (7.02 ± 0.22). The present study manifested that mild hypothermia and high cold strain experienced in humans during acute cold stress, impair memory and attention tests performance in more complex tasks (tasks requiring working memory, attention concentration, sustention and speed of information processing) while simple tasks remain unaffected (tasks requiring short-term memory and attention concentration for fast response).

Mechanism and Kinetics of Precipitation Process in Selected Copper Alloys

The required functional characteristics expected from copper alloys have a major impact on the technological production process, therefore there is a strong need to acquire knowledge on changes of properties with technological process including heat treatment and plastic working. The studied in this work copper CuTi4. CuFe2. CuCr0.7 and CuNi2Si1 alloys was selected to present differences in hardening phases .The samples were quenched, cold deformed (rolling), and aged. Detailed microstructure analysis and its influence on electrical and mechanical properties was presented in the work. Quenched CuTi4, CuFe2, CuCr0.7 and CuNi2Si1alloys have different mechanism and kinetics of precipitation during aging. These processes are complex and depend on the heterogeneity of distribution of alloying elements in copper matrix, the process parameters and cold strain value.

Microstructure Evolution in a Cu-Ag Alloy during Large Strain Deformation and Annealing

The structural changes and the strengthening of a Cu-3%Ag alloy subjected to large strain drawing and subsequent annealing were studied. The cold working was carried out at an ambient temperature up to total strain above 8. The hardness increased from 600 MPa in the initial state to about 1800 MPa with increasing the total strain. The annealing treatment at 400°C resulted in increase in the hardness to about 2000 MPa for the samples cold worked to total strains above 2. On the other hand, the hardness change of the samples annealed at 450°C dependent significantly on the preceding cold strain. Namely, annealing softening took place in the samples processed to strains below 5, while the samples processed to larger strains were characterized by remarkable hardening after annealing. The value of annealing hardening increased with increasing the previous cold strain, leading the hardness to 2500 MPa in the sample strained to 7.4. The cold worked and annealed samples were characterized by the development of lamella-type microstructure consisting of highly elongated copper grains with uniform distribution of nano-scaled silver particles having a size of about 2 nm.

Annealing behavior of a ferritic stainless steel subjected to large-strain cold working

Mechanisms of microstructure evolution during annealing after cold working were studied in an Fe-15%Cr ferritic stainless steel, which was processed by bar rolling/swaging to various total strains ranging from 1.0 to 7.3 at ambient temperature. Two types of recrystallization behavior were observed depending on the cold strain. An ordinary primary (discontinuous) recrystallization developed in the samples processed to conventional strains of 1.0–2.0. On the other hand, rapid recovery at early annealing resulted in ultrafine-grained microstructures in the larger strained samples that continuously coarsened on further annealing. Such annealing behavior was considered as continuous recrystallization.

Recovery and Recrystallization in Cold Worked Fe – O Steels

Several Fe – O samples containing different fractions of dispersed oxides were processed by mechanical milling followed by consolidating rolling. The samples were annealed at 1000oC and then compressed to strains of 0.35, 1.2, and 1.9 at an ambient temperature. Dispersed oxides with size of about 20 nm were homogeneously distributed throughout the ferrite matrix and their volume fractions varied from about 0.3% to 2.0%. To study the annealing softening mechanisms, the coldworked specimens were annealed for an hour at 700oC and 800oC. The fine dispersion of oxide particles was very effective to suppress any softening processes. Primary recrystallization fully developed in the samples with volume fraction of dispersed oxides of about 0.3%. Increase in the fraction of dispersed oxides resulted in decrease of the fraction recrystallized. In the samples containing 2.0 vol.% of dispersed oxides, only recovery was the annealing softening process irrespective of the preceding cold strain. The critical volume fraction of dispersed particles for development of the primary recrystallization is considered to range from 0.5 to 2.0%.