Vibrational control of electron-transfer reactions: a feasibility study for the fast coherent transfer regime

Electron donors are connectedvialeft and right bridges to electron acceptors. Following electron-transfer initiation, the IR excitation of selected bridge vibrational modes can tune the directionality of electron transfer.

Inter-arm coordination and intra-cyclic variation of the hip velocity during front crawl resisted swimming

AIM

The aim of the study was to assess the acute effect of front crawl sprint resisted swimming on the inter-arm coordination and the fluctuation of the swimming velocity.

METHODS

Nine female swimmers swam four all-out trials of 25 m, without and with low, moderate and high added resistance. Four camcorders were used to record the underwater movement. The inter-arm coordination was quantified using the index of coordination and the hip intra-cyclic velocity variation was analysed by calculating the coefficient of variation and the difference between the maximum and minimum velocities normalized for the mean stroke cycle velocity.

RESULTS

One-way repeated measures analyses of variance showed that swimmers change their inter-arm coordination from a "catch up" toward an "opposition" mode. Concerning the hip horizontal intra-cyclic velocity variation, it was increased significantly during resisted swimming.

CONCLUSION

These findings indicate that although resisted swimming cause an increase in the index of coordination and consequently it could be speculated a better propulsive continuity, the velocity fluctuations of the hip within a stroke cycle are not decreased, probably due to the inability of the swimmers to overcome effectively the concrete added resistances used in this study. Thus, at least concerning its acute effect, the hypothesis that the sprint resisted swimming could led to a technical improvement can not be satisfied.

Hand Orientation in Hand Paddle Swimming

The aim of this research was to study the effect of hand paddles on the pitch, the sweepback angles and other stroke kinematic characteristics of the hand during front crawl swimming. Ten female competitive swimmers swam without and with small (116 cm (2)) and large (268 cm (2)) paddles. Four cameras (60 Hz) were used to record the underwater strokes and the digitizing was undertaken using the Ariel Performance Analysis System. When the size of the paddles increased, the stroke length, the mean swimming velocity and the total duration of the stroke were significantly increased (p < 0.05), while the average velocity of the hand during the pull and the push phases were significantly decreased (p < 0.05). The stroke rate was decreased significantly (p < 0.05) only when using large paddles. The relative duration of the separate phases of the stroke, the magnitude of the medial-lateral displacements and the pitch and sweepback angles of the hand were not modified, indicating that the use of hand paddles did not caused significant alterations in the orientation and the movement of the hand during the underwater stroke in front crawl swimming.

The spectrum of segmental colitis associated with diverticulosis

BACKGROUND

Segmental colitis associated with diverticulosis (SCAD) has been defined as chronic colonic inflammation surrounding diverticula with rectal sparing. Distinguishing this condition from inflammatory bowel disease may be difficult. Our aim was to evaluate the epidemiological and clinical characteristics of SCAD in our area.

METHODS

Retrospective case identification with prospective follow-up was done. Patients with endoscopic findings suggestive of SCAD were enrolled. The epidemiological, clinical, and histological characteristics of these patients were analyzed.

RESULTS

Out of 605 patients with diverticulosis, 23 cases of SCAD were identified (3.8%). Four patients had histological characteristics suggestive of ulcerative colitis, in 1 case the histology was suggestive of ischemic colitis, 6 patients had histology compatible with SCAD, and the remaining patients had either transitional mucosa or minimal lesions. Four cases were refractory to conservative treatment (mesalamine and antibiotics) and surgery was required. No cases of extension of colonic inflammation in diverticula-free areas were found.

CONCLUSIONS

Segmental colitis associated with diverticulosis is not a rare disorder. It may occur with a spectrum of clinical and histologic features and may be confused with ulcerative colitis. The majority of the cases respond to medical therapy with antibiotics and/or mesalamine, whereas few cases are refractory and need surgery. No evolution to inflammatory bowel disease was observed.

Snatch lift kinematics and bar energetics in male adolescent and adult weightlifters

AIM

The aim of the present study was compare linear kinematics and energy changes of the barbell, along with the angular kinematics of the leg movement during the snatch technique, between male adolescent and adult weightlifters.

METHODS

Two S-VHS cameras operating at 60 fields per second recorded the heaviest lifts of 14 male adolescent and 9 adult top-level weightlifters under competitive conditions. The spatial co-ordinates of selected points on the body and the barbell were calculated using the direct linear transformation procedure. A low pass digital filter with 4 Hz cut-off frequency was used for the smoothing of raw co-ordinate data. The ''t''-test for independent samples was used for the statistical treatment of data.

RESULTS

The results revealed that there were no significant differences between the adolescent and the adult weightlifters in the majority of the kinematic variables. However, adolescent weightlifters extended their knees significantly slower (t21 = 4.211, p < 0.05) during the 1st pull and their ankles during the 2nd pull (t21 = 2.440, p < 0.05) than the adult weightlifters did. Moreover, the average relative power output was significantly greater for the adult weightlifters during both the 1st (t21 = 2.303, p < 0.05) and the snd pull (t21 = 2.611, p < 0.05).

CONCLUSION

These results indicate that the adolescent weightlifters were characterised from a high level of snatch technique and differentiated from the adults predominantly at the less powerful execution of the movement.