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排序方式: 共有850条查询结果,搜索用时 15 毫秒
1.
Here, we seek to determine how compliantly suspended loads could affect the dynamic stability of legged locomotion. We theoretically model the dynamic stability of a human carrying a load using a coupled spring-mass-damper model and an actuated spring-loaded inverted pendulum model, as these models have demonstrated the ability to correctly predict other aspects of locomotion with a load in prior work, such as body forces and energetic cost. We report that minimizing the load suspension natural frequency and damping ratio significantly reduces the stability of the load mass but may slightly improve the body stability of locomotion when compared to a rigidly attached load. These results imply that a highly-compliant load suspension could help stabilize body motion during human, animal, or robot load carriage, but at the cost of a more awkward (less stable) load. 相似文献
2.
Lucilia sericata has a facultative diapause in the third larval instar after cessation of feeding. Induction of the diapause is influenced by the photoperiod and temperature conditions experienced by insects in the parental generation as well as those experienced by the larvae themselves. The sensitive stage of the parental generation for induction of diapause was examined using diapause‐averting conditions of 16 h light : 8 h darkness (LD 16:8) at 25°C and diapause‐inducing conditions of LD 12:12 at 20°C. The incidence of diapause in the progeny was predominantly determined by the conditions experienced by the parents in the adult stage. Moreover, the results of reciprocal crosses showed that only the mother's experience is involved in the induction of diapause in the progeny. 相似文献
3.
Prashanth Sirigeri Jois 《Biochemical and biophysical research communications》2010,394(4):1036-1041
Bovine BSP5 belongs to the Binder of SPerm (BSP) family. BSP5 plays a role in the bovine sperm capacitation by promoting cholesterol and phospholipid efflux. The variable N-terminal part in the BSP proteins is the uncharacterized region with no known function. Full-length, N-terminal part, and individual fibronectin type II domains of bovine BSP5 were cloned, expressed and purified from Escherichia coli. His-S tagged N-terminal part showed large variation in migration on SDS-PAGE in comparison to other constructs. Using mass spectrometry it was demonstrated that the His-S-N-terminal part has the expected molecular mass (13 kDa). The recombinant N-terminal part was sensitive to E. coli endogenous proteases during purification. Denaturing purification involving boiling lysis of cells was carried out, as the protein was thermostable. The His-S-N-terminal part lacked structure as determined by CD analysis. Bioinformatics analyses confirmed that the N-terminal part of bovine BSP5 is intrinsically disordered. In addition, bioinformatics analysis indicated that rabbit BSP and multiple forms of BSP proteins of bovine and equine species possess partially or completely disordered N-terminus. The conservation of disorder at the N-terminus in BSP members belonging to different species suggests a role in biological process such as sperm capacitation and/or sperm-egg interactions. 相似文献
4.
R L Melnick L G Monti S M Motzkin 《Biochemical and biophysical research communications》1976,69(1):68-73
The mechanism of integration of λll, which is deleted of all the known λ recombination genes, was studied using deleted hosts as recipients. The presence of BC DNase and I in the recipient cells affected the fate of λll DNA. In nine of ten transductants, insertion of the λll genome took place somewhere between J and N and the remaining one had abnormally permuted prophage λ. In this lysogen (#42), the sequence of prophage genes was similar to that of vegetative phage λ. The properties of lysogen #42 were compared with those of other lysogens. 相似文献
5.
Three compounds capsaicin, curcumin and ferulic acid showing hypolipidemic activity have been tested in adult Wistar rats
fed high fat diets. Capsaicin (0.20 mg%) fed to female rats along with a 30% saturated fat diet lowered the rate of weight
gain, liver and serum triglycerides. In male rats it lowered only the liver and serum total and very low density and low density
lipoprotein triglycerides whether fed continuously for 13 or 8 weeks after interchanging the control and test diets from the
5th week onwards. Capsaicin fed to female rats in 30% mixed fat diet increased the rate of weight gain, lowered liver and
serum triglycerides, lowered adipose tissue lipoprotein lipase, elevated the hormone sensitive lipase and serum free fatty
acids. Capsaicin in 30% saturated fat diet lowered both the enzyme activities to a much lesser extent. Curcumin and ferulic
acid (both at 25 mg%) in 30% saturated fat diet tended to lower the rate of weight gain, liver total lipids and serum triglycerides.
It is of significance that a common dietary compound ‘capsaicin’ in the range of human intake triggers lipid lowering action
in rats fed high fat diets.
This paper was presented at the 55th Annual Meeting of the Society of Biological Chemists (India) held at Trivandrum during
December 15–17th, 1986. 相似文献
6.
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9.
Summary The Na+ requirement for active, electrogenic Cl– absorption byAmphiuma small intestine was studied by tracer techniques and double-barreled Cl–-sensitive microelectrodes. Addition of Cl– to a Cl–-free medium bathingin vitro intestinal segments produced a saturable (K
m
=5.4mm) increase in shortcircuit current (I
sc) which was inhibitable by 1mm SITS. The selectivity sequence for the anion-evoked current was Cl–=Br–>SCN–>NO
3
–
>F–=I–. Current evoked by Cl– reached a maximum with increasing medium Na concentration (K
m
=12.4mm). Addition of Na+, as Na gluconate (10mm), to mucosal and serosal Na+-free media stimulated the Cl– current and simultaneously increased the absorptive Cl– flux (J
ms
Cl
) and net flux (J
net
Cl
) without changing the secretory Cl– flux (J
sm
Cl
). Addition of Na+ only to the serosal fluid stimulatedJ
ms
Cl
much more than Na+ addition only to the mucosal fluid in paired tissues. Serosal DIDS (1mm) blocked the stimulation. Serosal 10mm Tris gluconate or choline gluconate failed to stimulateJ
ms
Cl
. Intracellular Cl– activity (a
Cl
i
) in villus epithelial cells was above electrochemical equilibrium indicating active Cl– uptake. Ouabain (1mm) eliminated Cl– accumulation and reduced the mucosal membrane potential
m
over 2 to 3 hr. In contrast, SITS had no effect on Cl– accumulation and hyperpolarized the mucosal membrane. Replacement of serosal Na+ with choline eliminated Cl– accumulation while replacement of mucosal Na+ had no effect. In conclusion by two independent methods active electrogenic Cl– absorption depends on serosal rather than mucosal Na+. It is concluded that Cl– enters the cell via a primary (rheogenic) transport mechanism. At the serosal membrane the Na+ gradient most likely energizes H+ export and regulates mucosal Cl– accumulation perhaps by influencing cell pH or HCO
3
–
concentration. 相似文献
10.
Vibration and sound communication in solitary bees and wasps 总被引:2,自引:0,他引:2
ABSTRACT. Females of solitary bees ( Colletes cunicularius L.) and of digger wasps ( Bembix rostrata L.) produce buzzing sounds and are known to secrete volatile odours when digging their way from the subterranean nests to the soil surface. The odours allow patrolling males to determine the approximate position of the digging virgin female. The buzzes are measured as substrate-borne sound (soil buzz vibrations) and as air-borne sound (soil buzz sounds). Play-back experiments suggest that the soil buzzes are used by the males as additional cues for localization. Faint buzz sounds are emitted regularly by the male during genital contact in copulation. They may serve to change the receptivity of the female. Intense and broadband buzz sounds are produced by bees of either sex, if restrained from moving, perhaps serving to deter predators. 相似文献