Cycling on Earth, in space, on the Moon

The mechanical power for cycling (P_c) at constant ground speed (s), in the absence of wind on smooth hard terrain is the sum of the power dissipated against rolling resistance, gravity and air resistance: P_c=a · s + M · g · s · sin γ + b · s ³, where a and b are constants, M is the mass of the subject plus bike, g is the acceleration of gravity and γ is the angle of the terrain with the horizontal. The constant b depends upon the drag coefficient (C_d), the overall area projected on the frontal plane (A _f), and the air density (ρ_a): b=0.5 · C_d · A _f · ρa. In turn, ρ_a depends on air pressure (P _B) and temperature (T): ρ_a=ρ₀ · 0.359 · P _B · T ⁻¹, where ρ₀ is the air density at 760 mmHg (101.3 kPa) and 273 K. The metabolic power developed by the cyclist (Ė _c) is related to P_c:Ė _c=P_c·η⁻¹, where η is the mechanical efficiency of cycling. The experimental values of a, b and η are fairly well known so that, if the maximal metabolic power as a function of the performance time is known for a given cyclist, the following set of data can be individually calculated: (1) best performances over any given distance and for any given altitude above sea level, (2) the effects of posture and body size on maximal speeds, and (3) the maximal incline of the terrain that can be overcome at any given speed or coasting speed for any given downslope. The above set of information makes it possible also to calculate the characteristics of a “Twin Bikes System” (TBS) for preventing microgravity deconditioning during long-term space flight. The TBS consists of two bicycles that are mechanically coupled by a differential gearing, which move at the very same speed, but in the opposite sense, along the inner wall of a cylindrically shaped space module. The circular trajectories induce a centrifugal acceleration vector (a _c) oriented along the head-to-feet direction of each subject: a _c=v _t ² · r ⁻¹ where v _t is the tangential velocity and r the radius of gyration, which is equal to the inner radius of the space module. So, any desired value of a _c can be achieved by appropriately selecting v _t, wherefrom the mechanical and metabolic powers that the astronauts must generate can be readily calculated. Experiments performed in a ground-based human centrifuge have shown that the discomfort derived from the rotating environment is reasonably low and well tolerated. If the appropriate atmospheric pressure is provided, cycling on circular or elliptical tracks may be useful to reduce cardiovascular deconditioning that occurs due to the reduced gravity in permanently manned lunar bases. Indeed, on the curved parts of the path a cyclist will generate a horizontal outward acceleration: a _c=s ² · r ⁻¹, where s is the velocity along the track and r is the radius of curvature. To counterbalance a _c, the subject plus bike must lean inwards so that the vectorial sum of a _c plus the lunar gravity (g _L=1.62 m · s⁻²) is applied along a straight line that includes the centre of mass of the system and the point of wheel contact with the ground. For values of s from 10 to 20 m · s⁻¹ and r from 50 to 200 m, this vectorial sum ranges from 1.05 to 5.03 g _L (0.17–0.83 g). Accepted: 20 March 2000     

Birth order effects on dermatoglyphs on fingers,palms, toes,and soles

Coefficients of correlation of 47 dermatoglyphic traits with birth order vary widely in a sample of 145 sibships of a Bengali speaking population. In general, ridge-counts and pattern intensities tend to decrease with birth order. Linear effects of birth order are, however, significant in samples of two sexes only for ridge-counts on the ab regions of palms and on toes, and in males only for triradial number on toes, D-line exit, hallucal ridge-count and triradial number on soles, and ridge-count on index fingers. Their relative intensities do not follow the order of appearance or of heritabilites of the traits. The maximal atd angle, which has a negligible correlation with birth order, shows no consistent trend of a linear or non-linear change with birth order in the two sexes even within sibships.     

支气管哮喘病人胸导管淋巴液与血清IL-6、IL-8、 IL-10、IL-12、TNF-α水平的对比研究

目的：探讨哮喘病人胸导管淋巴液和血清IL-6、IL-8、IL-10、IL-12及TNF-α水平变化。方法：采用酶联免疫吸附试验（ELISA）检测31例行胸导管引流治疗的中、重度哮喘病人术后0 d、3 d、5 d淋巴液及0 d、5 d血清IL-6、IL-8、IL-10、IL-12以及TNF-α水平。结果：哮喘病人胸导管引流淋巴液中IL-6、IL-8、IL-10、TNF-α水平均高于正常对照组血清水平，而IL-12则明显低于正常血清水平；引流5 d淋巴液中IL-6、IL-8、IL-10及TNF-α明显低于，IL-12则显著高于引流0 d时水平；同时哮喘病人血清IL-10、TNF-α含量低于，血清IL-12则高达正常对照组水平。结论：哮喘病人淋巴液中存在以IL-12产生受抑和炎性细胞因子产生亢进为特征的细胞因子失调，且淋巴液中CK变化与血清变化大致平行。     

Effect of ischemia, hypertrophy, hypoxia, acidosis, and alkalosis on canine defibrillation

Our purpose was to assess the effect of myocardial ischemia, left ventricular hypertrophy, and systemic hypoxia and acid-base abnormalities on the energy requirements for defibrillation. We determined the defibrillation threshold (DFT), the minimum energy required to defibrillate. DFT was not significantly elevated after left anterior descending coronary occlusion, nor was there a relationship between the size of the occluded coronary distribution area (coronary risk area) and the change in DFT in individual animals. Renal hypertension and left ventricular hypertrophy were induced by unilateral nephrectomy and contralateral renal artery stenosis. DFT in left ventricular hypertrophy dogs was not significantly higher than in dogs without hypertrophy. Finally, we induced systemic hypoxia and acid-base abnormalities. Neither respiratory nor metabolic acid-base disturbances affected DFT, but during systemic hypoxia (O2 tension 45 +/- 2) DFT fell from 83 +/- 49 to 58 +/- 28 J (P less than 0.01). Thus in dogs, myocardial ischemia, left ventricular hypertrophy, and acid-base abnormalities do not elevate defibrillation energy requirements, whereas hypoxia reduces the energy needed to defibrillate.     

Update on vitamins, minerals, and the carotenoids

Various vitamins and minerals play roles in HIV infection. There is evidence that a number of HIV+ patients suffer from deficiencies in vitamins B12, B6, A, and D; folate, zinc and selenium; and carotenoids such as beta-carotene, betacryptoxanthin, and lutein. Vitamin B12 deficiency can result in peripheral neuropathy, encephalopathy, cognitive dysfunction and anemia. Lowered levels of vitamins B6 and A can lead to impaired immune function and, in the latter, an increased rate of perinatal transmission. Low levels of vitamin D have been linked to weight loss and wasting. Folate deficiencies are related to anemia, and low levels of zinc and/or selenium have been linked to impaired immune function. Information on the carotenoids, which have been found to be associated with cellular immune function, is mostly derived from recent research. Studies have shown that the levels of carotenoids are decreased in HIV+ people even in the early stages of infection, but the greatest deficiencies appeared in patients with the most advanced disease. Other clinical trials seem to indicate that administration of beta-carotene improves immune function, causing an increase in CD4 counts over baseline levels. Clinical trials conducted in response to all of these deficiencies have found multivitamin supplementation to be beneficial. Therefore, it is recommended that all HIV-infected patients receive a multivitamin supplement to assist in reversing the damage caused by these vitamin and mineral deficiencies.