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•New mechanism for the formation of HAP layer using sonocoating method was reported.•It was proved that HAP layer grows laterally, forming dendrite-like patterns.•HAP layer structure ...depends on nanoparticle size and coating duration.•Sonocoating polymer surface with HAP greatly improved hydrophilicity properties.•Sonocoating takes place in water at 30 °C and process duration is only 8 min.
A mechanism is described for coating a polymer surface with nanoparticles (NPs) using high-power ultrasound acting on NPs suspended in liquid. The process is called “sonocoating”. Nano-hydroxyapatite (HAP) NPs are used for sonocoating in this study. In the sonocoating process, according to the known “throwing stones” mechanism, liquid microjets created when cavitation bubbles implode randomly throw NPs towards the surface. In our studies, the nano-HAP layer grows laterally, forming dendrite-like patterns. We propose that the liquid streams generated by cavitation bend close to the surface and move the HAP NPs parallel to the surface. The layer nucleates when the NPs gather at surface imperfections. Subsequently, the layer grows laterally by preferential attraction of HAP NPs to the layer edges. The layer structure depends on the size of the HAP NPs and the coating duration. NPs with a mean diameter of 15 nm form a homogeneous layer faster than those with a mean diameter of 45 nm. Sonocoating is an extraordinary method for producing nano-HAP layers, since the coating takes place in water at 30 °C and the process duration is only 8 min.
This research aims at studying the effect of comparative feedback on psychological variables (competence valuation, perceived competence, autonomous motivation, amotivation, subjective well-being) ...and performance (throwing speed and accuracy). A total of 73 handball players from the highest Spanish handball (Iberdrola League) category participated in this study. After previously rating satisfaction with their head coach, they were indiscriminately assigned to one of three different experimental conditions measuring feedback, positive, negative, and none. There were significant differences in competence valuation, perceived competence, autonomous motivation, and throwing speed in the three feedback groups, more concretely, low satisfaction with the head coach. Positive effects were found when there was low satisfaction with the coach and positive feedback on the competence valuation, autonomous motivation, and throwing speed compared to negative or no feedback. These results have important implications for optimizing coaches’ behaviors in relation to athlete well-being and performance.
In a ball catching task, the catcher guides their hand to the ball's future trajectory. The hand may start to move even before the exact position is known, and the interceptive movement may be ...corrected online. Using a recent method for detecting the phases of catching movements we investigate how juggling experience, self-throwing, and delayed visibility of the ball, influence the timing of the hand's trajectory. Specifically, we analyze the time from which the goal position of the movement is known, i.e., the time from which the movement becomes smooth. Seventeen jugglers and twenty controls caught ten balls per each of eight conditions. The results indicate that experts' catching movements acquire the smooth nature of goal-directed movements earlier than novices catching movements do.
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Dostopno za:
BFBNIB, DOBA, FSPLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The term shoulder instability refers to a variety of mechanisms and clinical presentations. One of the common pathologies of throwing disorders is internal impingement with anterior instability. Most ...throwing athletes with symptomatic internal impingement with anterior instability exhibit positive apprehension and relocation test results, whereas those with recurrent anterior shoulder instability display positive apprehension test results. While the glenoid labrum-inferior glenohumeral ligament complex is a significant critical stabilizer for the prevention of anterior shoulder dislocation, the characteristics of the essential lesion in internal impingement with anterior instability have not been determined yet. This study aimed to compare the intra-articular lesion of athletes with internal impingement related to the overhead throwing motion in athletes with a traumatic shoulder dislocation.
Sixty-one athletes (all men; mean age, 25.2 ± 12.6 yr) who underwent an arthroscopic procedure were divided into 2 groups: 25 in the throwing group and 36 in the dislocation group. All shoulders had subtle glenohumeral instability defined by a positive anterior apprehension test and a relocation test. Those with voluntary and multidirectional instability and large glenoid bone loss (more than 25%) were excluded from the current study. All shoulders were evaluated for the following evidence: rotator cuff injury, superior labrum tear anterior and posterior lesions, labral pathologies including Bankart lesions, osteochondral lesions to the humeral head, biceps tendon fraying or rupture, and inferior glenohumeral ligament and middle glenohumeral ligament (MGHL) conditions.
Arthroscopic findings of the throwing group showed more supraspinatus injuries (92% and 25%, P < .001), type II superior labrum tear anterior and posterior lesions (60% and 3%, P < .001), posterosuperior labral lesions (92% and 39%, P < .001), and hypoplastic MGHLs (56% and 6%, P < .001) and lesser Bankart lesions (8% and 92%, P < .05) than those of the dislocation group.
These results indicate that the characteristic lesions of internal impingement with anterior instability in throwing athletes include partial thickness rotator cuff tears, superior labrum tear anterior and posterior lesions, posterosuperior labral tears, and hypoplastic MGHLs. As expected, the physiopathology of internal impingement with anterior instability in throwing athletes may be related to the dysfunction of the anterosuperior glenohumeral capsular ligament, including the MGHL, rather than the inferior glenohumeral ligament as in traumatic anterior shoulder dislocations. These findings would be useful for defining treatment strategies for internal impingement with anterior instability in overhead throwing athletes.
The poor preservation of Palaeolithic sites rarely allows the recovery of wooden artefacts, which served as key tools in the arsenals of early hunters. Here, we report the discovery of a wooden ...throwing stick from the Middle Pleistocene open-air site of Schöningen that expands the range of Palaeolithic weaponry and establishes that late Lower Palaeolithic hominins in Northern Europe were highly effective hunters with a wide array of wooden weapons that are rarely preserved in the archaeological record.
This paper discusses about the measurement of optimization on feeder machine with automatic system control for aquaculture. This paper mainly aims to observe four main parts of feeding machine of ...aquaculture: major inlet, scale system, spiral tunnel, and throwing system. The observation done includes the energy of electricity usage of each unit of feeding weight which is processed, duration of process of each part, the exchange of rotor speeds, and the flow of feeding speed rate in gram per second. In this research, the design of feeding machine with automatic system based on Arduino Uno is conveyed. The feeds size used in this research are 2mm and 4mm. The measurement of optimization aims to consider the weight of the feeds, and the system of machine that works optimally. The result from experiment releases that the machine designed is able to work optimally on 2kg feeds of each process in 70 seconds and 71 seconds, and 0.085Wh on energy of electricity usage.
Weighted-ball velocity training programs are popular but may be associated with increased injury risk. The purpose of this study was to determine the current frequency of these programs, as well as ...their association with range of motion, strength, velocity, injury, and utilization in high school baseball pitchers.
This was a multicenter, prospective, community-based study including high schools from the Northeastern, Southeastern, Midwestern, and Western regions of the United States. Preseason pitchers were surveyed about their use of weighted ball velocity programs and history of injury. Preseason pitchers underwent standardized physical examinations and pitch velocity was measured. During a single high school season, pitch counts and injury incidence were prospectively collected.
In total, 115 pitchers were recruited, of whom 63% had participated in a weighted ball program. There were no differences in range of motion or strength between groups who used weighted balls and those who did not. Pitchers that utilized weighted ball programs demonstrated a higher average fastball velocity (114.26 vs. 106.22 km/h 71 vs. 66 mph; P < .001) as well as peak fastball velocity (115.87 vs. 109.44 km/h 72 vs. 68 mph; P = .001) compared to those that did not use weighted ball programs. Pitchers that utilized weighted ball programs were no more likely to be single-sport athletes (44%) than those who were multisport athletes (49%, P = .667). Within the group who had used a weighted ball program 29% (13/45) reported a history of injury and within the group who had not used a weighted ball program 25% (10/40) reported a history of injury (P = .687). As only a single injury occurred in the entire cohort, comparison of injury rates could not be completed.
In this prospective study, the majority of high school pitchers reported using weighted ball programs to increase velocity, and these programs were associated with increased average and peak velocity compared to pitchers who did not use weighted ball programs. There were no significant differences in injury history between the 2 groups. Further study is necessary to understand the injury risk associated with weighted ball programs.
Today, abrasive blasting is experiencing rapid development, due to two important factors. The first one is related to the introduction of the throwing wheel as an element that sets the granular media ...in motion directing them to the treated surface, while the second factor is related to the production of modern machining media. Together, these factors make blasting one of the most efficient mechanical surface preparation methods. Unfortunately, the high erosiveness of the abrasive stream, so appreciated in the process of preparing the treated surface, also contributes to significant wear of the elements in its immediate vicinity. The undertaken issues focus on the possibilities of classifying various states of the throwing wheel of a rotary machine tool based on the analysis of its dynamic properties.
This study aims to examine the relationship between postural perfor-mance, physical fitness level, and shooting performance in Olympic fe-male goalball players. Eight Olympic-level goalball players ...(age: 20.63± 4.37 years) were recruited from the Turkish National Women’s Goalball Team. Postural stability, physical fitness, and shooting performance of the players were measured. The postural stability was determined us-ing body sway measurements during parallel and single-leg stances on a force plate. The physical fitness level of the players is evaluated by curl-up, isometric push-up, trunk lift, and grip strength (dominant hand) tests. A goalball-specific shooting accuracy test was used for shooting performance. Independent sample t-test and Pearson correlation were used for statistical processing. No statistical difference was observed in body sway parameters between open eyes and closed eyes condi-tions except for the anteroposterior sway area. Some of the body sway parameters performed under different stances positively correlated with all physical fitness tests (P<0.05). There was a positive correlation between the shooting accuracy and trunk lift score (r=0.767). Right leg sway area anterior-posterior and ellipse area negatively correlated with shooting accuracy (r=-0.629 and r=-0.692 respectively). It is necessary to attach importance to the improvement of the physical fitness level specific to core strength to maintain postural stability for visually im-paired athletes. In our study, some factors affecting shooting accuracy were identified, but it is necessary not to restrict a complex structure such as shooting accuracy within certain concepts.
Little is known about the process of the invention of the prehistoric spear thrower which appeared around 25,000 years ago in Europe, although it may have emerged earlier on other continents. This ...innovative weapon had a late arrival in Australia from Papua New Guinea at the end of the late glacial maximum, and probably induced an adaptation in hand throwing spear technology used by local people. But could the spear thrower have also originated independently from older prehistoric technology on this continent? In this work, the hypothesis of a technological evolution from throwing sticks to the spear thrower is examined through several particular wooden Australian Aboriginal implements observed in ethnographic collections. Indeed, some traditional Aboriginal hooked throwing sticks from Coopers Creek might be a trace of a prehistoric throwing stick/spear thrower technological complex which has disappeared to be replaced by true specialised spear throwers from New Guinea, rendering them obsolete. Interestingly, other intersections between these two weapons could be found in the particular type of “on edge” built Aboriginal spear throwers from Northern Queensland where rare examples of spear throwers made from modified throwing sticks can also be found. Do they result from an adaptation of throwing sticks in contact with spear thrower importations from New Guinea or do they reflect the continuity of an older, independent Indigenous Australian spear thrower invention? Experimental replicas and throwing tests have been used here to try to shed light on the potential and limits of such implements which could have been used simultaneously for both functions.
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