Search

In the classical theory of the Secchi disk depth, diffuse sunlight falling on the disk is reflected back to the observer's eye along the most direct route, as a beam. The disappearance depth, ZSD, of the disk is then expected to vary inversely with the sum of the beam and diffuse attenuation coefficients: c + KD. Observations presented here show that, in the most turbid waters sampled, the Secchi disk is visible at greater depths (by a factor of up to 4) than predicted by this theory. In these conditions, the disk appears blurry, and it seems likely that some of the light reflected by the disk returns to the eye as diffuse light, photons being scattered one or more times on their journey from the disk surface to the observer. We have modified the theory of the Secchi disk in turbid water to allow for a mixture of beamed and diffuse light contributing to disk visibility. The modified theory corrects the under‐estimate of Secchi depths in turbid waters and gives good agreement with observations over a wide range of turbidity. The insight gained allows a more informed interpretation of Secchi disk measurements in turbid water. [ABSTRACT FROM AUTHOR]

Abstract: Aim: The potential for tendinous tissues to adapt to functional overload, especially after several years of exposure to heavy‐resistance training, is largely unexplored. This study compared the morphological and mechanical characteristics of the patellar tendon and knee extensor tendon‐aponeurosis complex between young men exposed to long‐term (4 years; n = 16), short‐term (12 weeks; n = 15) and no (untrained controls; n = 39) functional overload in the form of heavy‐resistance training. Methods: Patellar tendon cross‐sectional area, vastus lateralis aponeurosis area and quadriceps femoris volume, plus patellar tendon stiffness and Young's modulus, and tendon‐aponeurosis complex stiffness, were quantified with MRI, dynamometry and ultrasonography. Results: As expected, long‐term trained had greater muscle strength and volume (+58% and +56% vs untrained, both P < .001), as well as a greater aponeurosis area (+17% vs untrained, P < .01), but tendon cross‐sectional area (mean and regional) was not different between groups. Only long‐term trained had reduced patellar tendon elongation/strain over the whole force/stress range, whilst both short‐term and long‐term overload groups had similarly greater stiffness/Young's modulus at high force/stress (short‐term +25/22%, and long‐term +17/23% vs untrained; all P < .05). Tendon‐aponeurosis complex stiffness was not different between groups (ANOVA, P = .149). Conclusion: Despite large differences in muscle strength and size, years of resistance training did not induce tendon hypertrophy. Both short‐term and long‐term overload demonstrated similar increases in high‐force mechanical and material stiffness, but reduced elongation/strain over the whole force/stress range occurred only after years of overload, indicating a force/strain specific time‐course to these adaptations. [ABSTRACT FROM AUTHOR]

Introduction Coated platelets are a subpopulation of platelets that possess highly prothrombotic properties. Previous observational data suggest that bleeding phenotype in severe haemophilia A is associated with coated platelet levels. Haemophilia A patients with higher coated platelet levels may have a mild bleeding phenotype; those with lower levels may have a more severe bleeding phenotype. Aim The aim of the study was to test the hypothesis that coated platelet levels are correlated with clinical bleeding phenotype. Methods This cross-sectional, observational study enrolled 20 severe haemophilia A patients, including 15 with severe and five with a mild bleeding phenotype, and a control group of 12 healthy volunteers. The haemophilia bleeding phenotype was determined by the patient's medical history and haemophilia treatment centre records. Blood was obtained from each patient by venipuncture and platelets were analysed by flow cytometry. Results Patients categorized as having a severe bleeding phenotype experienced a median eight bleeds per year compared to one bleed annually in the mild bleeding phenotype group. Both groups had similar total platelet counts and fibrinogen levels. There was no difference in coated platelet percentage between severe and mild bleeding phenotype (17 and 16% respectively), however, both groups had significantly lower % coated platelets compared to controls (44%, P < 0.0001). Conclusion Coated platelet levels were not associated with bleeding phenotype in this study; however, these data may suggest coated platelet levels are lower in haemophilia patients relative to healthy volunteers. [ABSTRACT FROM AUTHOR]

New Findings: What is the central question of this study? Does contraction influence the fascicle length, pennation angle and effective physiological cross-sectional area (eff PCSA) of the quadriceps femoris muscle? Is there a stronger relationship between eff PCSA and maximal strength if eff PCSA is measured during maximal contraction rather than at rest? What is the main finding and its importance? Fascicle length decreased, pennation angle increased and eff PCSA increased in a non-linear manner with isometric torque. The eff PCSA during maximal contraction and rest were correlated in a similar manner to maximal strength. The eff PCSA at rest is sufficient to characterize the muscle size-strength relationship. The primary purpose of this study was to document the influence of muscle contraction on quadriceps femoris (QF) muscle architecture [fascicle length (Lf ) and pennation angle (θp )] and effective physiological cross-sectional area (eff PCSA). Secondarily, we aimed to determine whether eff PCSA measured during maximal voluntary contraction (MVC) had a stronger relationship to maximal strength than eff PCSA at rest. Fifteen young men performed a series of voluntary knee-extension isometric ramp contractions. Isometric maximal voluntary torque (MVT) was recorded during separate MVCs. Measurements of architecture and eff PCSA of each constituent muscle of the QF and, subsequently, the whole QF were made at rest, during 20% increments of maximal voluntary torque and during an MVC. The QF muscle architecture and morphology changed in a curvilinear manner with relative torque (%MVT), with significant differences being observed between incremental torque levels for Lf , θp and eff PCSA. Specifically, from rest to MVC, QF Lf decreased (-23.5 ± 3.3%), whereas θp increased (+39.7 ± 6.6%). The QF eff PCSA was +26.5 ± 5.7% greater during MVC than at rest. Similar moderate correlations existed for MVT and eff PCSA at rest (r = 0.519, P = 0.047) and for MVT and eff PCSA during MVC (r = 0.530, P = 0.042). Substantial changes in QF architecture (Lf , θp ) and eff PCSA occur in a curvilinear manner with relative torque production. The eff PCSA during MVC was no more strongly associated with MVT than eff PCSA measured at rest, which implies that resting measurements of muscle size are suitable for characterizing the muscle size-strength relationship., (© 2015 The Authors. Experimental Physiology © 2015 The Physiological Society.)

In 1979, a pilot survey defined respiratory status and unmet health care needs of retired and former male asbestos workers in Hawaii. Of 1,401 identified subjects, 741 were contacted and 411 were interviewed. Forty-five subjects were between 39 and 54 years of age; 208, between 55 and 64; and 158, age 65 or more. They represented the main ethnic groups--Caucasian, Chinese, Filipino, Hawaiian and part-Hawaiian, and Japanese--on Oahu. Most subjects had had significant exposure to asbestos in a shipyard, and 83% were current nonsmokers (160 had never smoked, and 111 were ex-smokers for ten years or more). Taking age and ethnicity into account, our group had more chronic respiratory and gastrointestinal problems than the comparable male population of Oahu in 1979, but fewer such problems than active shipyard workers elsewhere. These problems related primarily to current smoking status and secondarily to the length of asbestos exposure. Health care was available, but former workers used it less than retirees, despite having more symptoms. Very few abnormalities were reported by the subjects on their chest X-rays, pulmonary function tests, and sputum cytology performed elsewhere. These findings are compared to those of other shipyards, and support the hypothesis that the biological effects of asbestos exposure are generally mild in Hawaii.