Sliding on carbon nanotube arrays

Adhesion, friction and wear of Single-Walled Nanotube (SWNT) and multi-walled nanotube arrays have been investigated. SWNT arrays exhibit lower adhesion and friction values on account of the lower van der Waals’ forces resulting from lower packing density and higher flexibility. Wear tests show that both arrays do not wear. Tip wear and friction force in the SWNT array are lower due to lower adhesion and higher flexibility of the SWNTs, which lead to less resistance to the motion of the tip.     

Effect of thermoelectric magnetic force on the array of dendrites during directional solidification of Al–Cu alloys in a high magnetic field

By eliminating the effect of the magnetic moment arising from the magnetic crystalline anisotropy, the effect of the thermoelectric magnetic force on the array of dendrites during directional solidification of Al–35?wt%Cu and Al-40?wt%Cu alloys in a high magnetic field has been investigated experimentally. The results indicate that the dendrite array is essentially destroyed, a result that could have general significance for understanding the processes involved in the solidification of alloys in a magnetic field.     

Life: Definition,Origin, and Evolution

Out of all the natural phenomena surrounding us, the phenomena Life, as a matter of course, is that which is the most mysterious and least understood of all. In many aspects, it seems as though it would be possible to investigate, study, and explain Life, like so many of the other subjects that fall within the category of the natural sciences: time, space, mass, movement, and so on. However, in its essence, Life is organized and managed differently than all other natural phenomena, operating, as it were, according to its own laws. Life certainly has certain clearly recognizable characteristics, such as: metabolism, homeostasis, continuity, and more. However, up until the present time, no definition for Life has been provided, which unifies it as an entity, and differentiates it unmistakably from other natural phenomenon. The current article offers a definition of the true nature of the phenomenon of Life, which in turn helps to explain the big questions of life—evolution, the mind–body problem, consciousness, and more.     

Bilateral Transfer in Tapping Skill in the Absence of Peripheral Information

Bilateral transfer in a fast tapping task was investigated under normal (+FB) and reduced (-FB) feedback conditions, in the -FB experiment 36 Ss were assigned to 3 groups: preferred (PH) to non-preferred (NPH) shift; NPH to PH; and alternating trials of PH and NPH. With + FB 2 further groups of 12 Ss transferred PH to NPH or NPH to PH. 8 preshift and 8 postshift trials were given. The alternating group had 8 PH and 8 NPH trials. In preshift performance increment was found in ail groups except in +FB with NPH. With +FB some facilitation in transfer was obtained for the NPH; under -FB marked positive transfer was found for the PH. Alternating PH and NPH performance conformed to preshift levels. Results were discussed in terms of differential central control processes for the two hands.     

Latency and Response Complexity

Two experiments were conducted in which the latency of movement responses of varying complexity was investigated. The complexity of an arm sweep movement was varied by (a) increasing the extent of movement from 6 in. to 18 in., (b) reversing the movement, and (c) by making two or three pauses in an on-going movement. The results only partially supported the hypothesis that the latency of a response is related to the complexity of the movement pattern. Specifically RT was longer when the response involved significant changes in the temporal organization of the movement pattern.     

Motor Performance and Response Consistency as a Function of Age

The specificity versus generality of motor performance and motor response consistency was investigated as a function of age. 120 Ss, 30 each at age 7, 11, 15, and 19 yr., were given 120 practice trials (60 trials per session with 24 hr interpolated between sessions) on both simple and choice RT tasks. For motor performance the reliability of individual differences was high in both tasks at all ages, while the amount of generality was moderately high in the two younger groups but diminished with age. The reliability coefficients for motor response consistency were low for both tasks but, with two exceptions, statistically significant. There was no evidence for generality in motor response consistency at any age.     

Dynamics of Pushing

A standing individual can use several strategies for modulating pushing force magnitude. Using a static model, researchers have shown that the efficacy of those strategies varies considerably. In the present article, the authors propose a human motor control dynamic model for analyzing transients that occur when an individual is asked to modulate force magnitude. According to the model, the impedances of both the upper and the lower limbs influence the time course of force variations and foot placement has a profound effect on pushing force dynamics. With a feet-together posture, the center of pressure has a limited range of motion and changes in force may be preceded by initial changes in the opposite direction; that is, to decrease force, an individual must first increase force. When the feet are placed apart, individuals can move the center of pressure over a much larger range, thereby modulating pushing force magnitude, without reversing behavior, over a larger range of force magnitudes. Therefore, the best way to control pushing force at the hand may be by using the foot.     

Trends in optimization models of sales force management

In the last half-century, significant advances have been made in directing sales force behavior with the use of optimization and decision models. The present paper both presents the current state-of-the art in sales force decision modeling, and also discusses key issues and trends in contemporary modeling of relevance to sales force researchers. The paper begins by exploring critical concepts regarding the estimation of the sales response function, and then discusses critical problems of endogeneity, heterogeneity, and temporal variation that are faced by modelers in this task. Modern approaches to dealing with these issues are presented. We then discuss areas of importance concerning finding model solutions, including closed form versus simulation, and optimization versus heuristic solutions. The paper next moves to areas of practical importance where models can help, including call planning, sales force size, territory allocation, and compensation design. Finally, we discuss trends that will likely impact on sales force modeling in coming years, including the use of big data and data mining, the possible breakdown of rationality, the rise of the Internet and social media, and the potential of agent-based modeling.     

Similar changes in muscle fiber phenotype with differentiated consequences for rate of force development: Endurance versus resistance training

Resistance training has been shown to positively affect the rate of force development (RFD) whereas there is currently no data on the effect of endurance training on RFD. Subjects completed ten weeks of either resistance training (RT, n = 7) or endurance cycling (END, n = 7). Pre and post measurements included biopsies obtained from m. vastus lateralis to quantify fiber phenotype and fiber area and isokinetic dynamometer tests to quantify maximal torque (Nm) and RFD (Nm/s) at 0–30, 0–50, 0–100 and 0–200 ms during maximal isometric contraction for both knee extensors and flexors. Both groups increased the area percentage of type IIa fibers (p < .01) and decreased the area percentage of type IIx fibers (p = .05), whereas only RT increased fiber size (p < .05). RT significantly increased eccentric, concentric and isometric strength for both knee extensors and flexors, whereas END did not. RT increased 200 ms RFD (p < .01) in knee flexor RFD and a tendency towards an increase at 100 ms (p < .1), whereas tendencies towards decreases were observed for the END group at 30, 50 and 100 ms (p < .1), resulting in RT having a higher RFD than END at post (p < .01). In conclusion, resistance training may be very important for maintaining RFD, whereas endurance training may negatively impact RFD.