Exploring other surrogate markers     

Cohen J 《Science (New York, N.Y.)》1992,258(5081):389

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HIV and heroin: a deadly international affair: Vietnam     

Cohen J 《Science (New York, N.Y.)》2003,301(5640):1657-1658

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The effect of algal symbionts on the accuracy of Sr/Ca paleotemperatures from coral     

Cohen AL  Owens KE  Layne GD  Shimizu N 《Science (New York, N.Y.)》2002,296(5566):331-333

The strontium-to-calcium ratio (Sr/Ca) of reef coral skeleton is commonly used as a paleothermometer to estimate sea surface temperatures (SSTs) at crucial times in Earth's climate history. However, these estimates are disputed, because uptake of Sr into coral skeleton is thought to be affected by algal symbionts (zooxanthellae) living in the host tissue. Here, we show that significant distortion of the Sr/Ca temperature record in coral skeleton occurs in the presence of algal symbionts. Seasonally resolved Sr/Ca in coral without symbionts reflects local SSTs with a temperature sensitivity equivalent to that of laboratory aragonite precipitated at equilibrium and the nighttime skeletal deposits of symbiotic reef corals. However, up to 65% of the Sr/Ca variability in symbiotic skeleton is related to symbiont activity and does not reflect water temperature.  相似文献   

Economics. Learning with regret     

Cohen MD 《Science (New York, N.Y.)》2008,319(5866):1052-1053

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Prediction of new low compressibility solids   总被引：1，自引：0，他引：1  

Liu AY  Cohen ML 《Science (New York, N.Y.)》1989,245(4920):841-842

An empirical model and an ab initio calculation of the bulk moduli for covalent solids are used to suggest possible new hard materials. The empirical model indicates that hypothetical covalent solids formed between carbon and nitrogen are good candidates for extreme hardness. A prototype system is chosen and a first principles pseudopotential total energy calculation on the system is performed. The results are consistent with the empirical model and show that materials like the prototype can have bulk moduli comparable to or greater than diamond. It may be possible to synthesize such materials in the laboratory.  相似文献   

Dynamic modification of the vestibulo-ocular reflex by the nodulus and uvula   总被引：4，自引：0，他引：4  

W Waespe  B Cohen  T Raphan 《Science (New York, N.Y.)》1985,228(4696):199-202

The time constant of the decay of slow-phase eye velocity of postrotatory nystagmus or optokinetic after-nystagmus is reduced during exposure to a stationary visual surround (visual suppression). It is also reduced after tilting the head (tilt suppression). A "dump" mechanism in the vestibulo-ocular reflex has been proposed to rapidly discharge activity from the central vestibular system during both types of suppression. Monkeys lost this mechanism after lesions of the nodulus and uvula. They also lost the ability to habituate the time constant of nystagmus on repeated exposure to optokinetic and vestibular stimuli. Periodic alternating nystagmus, which is believed to represent an instability in the vestibulo-ocular reflex, was observed in two of three monkeys. These data indicate that the nodulus and uvula play an important role in suppressing, habituating, and stabilizing the vestibulo-ocular reflex.  相似文献   

Electrical responses of insect central neurons: augmentation by nerve section or colchicine   总被引：3，自引：0，他引：3  

R M Pitman  C D Tweedle  M J Cohen 《Science (New York, N.Y.)》1972,178(60):507-509

Intracellular recording from the somata of central motor neurons in the cockroach Periplaneta americana normally shows little or no electrical response evoked by soma depolarization or by antidromic stimulation. Within 4 days after either cutting the axon or administration of colchicine, large action potentials can regularly be recorded from cell bodies of metathoracic motor neurons. Each experimental procedure evokes formation of a dense, perinuclear ribonucleic acid ring in the soma of neurons showing augmented electrical responses.  相似文献   

Interferometer experiment with independent local oscillators   总被引：1，自引：0，他引：1  

Bare C  Clark BG  Kellermann KI  Cohen MH  Jauncey DL 《Science (New York, N.Y.)》1967,157(3785):189-191

We have operated an interferometer with independent local oscillators and without any communication link of wide bandwidth between the elements of the interferometer. This makes operation possible at very long base lines because, heretofore, construction of the communications link has been the factor limiting the separation of the elements. In our system, coherence at the two elements is maintained through the use of two highly stable, atomic oscillators. The intermediate-frequency output signals are recorded at each element on a high-speed digital tape recorder. Interference fringes are produced later by cross-correlating the two tape records in a digital computer.  相似文献   

Thyroxine interaction with actinomycin D and possible biological implications     

K H Kim  L M Blatt  P P Cohen 《Science (New York, N.Y.)》1967,156(772):245-246

Actinomycin D and thyroxine interact in solution (pH 8 to 10), as revealed by changes in the absorbance of actinomycin D. Thyroxine can prevent the growth-inhibitory effect of actinomycin D on Bacillus subtilis if it is present in a molar ratio of 3000 (thyroxine to actinomycin D).  相似文献   

Electrical sources in human somatosensory cortex: identification by combined magnetic and potential recordings   总被引：7，自引：0，他引：7  

C C Wood  D Cohen  B N Cuffin  M Yarita  T Allison 《Science (New York, N.Y.)》1985,227(4690):1051-1053

Magnetic fields and electrical potentials produced by neuronal activity have different properties that can be used for the identification of electrical sources in the human brain. Fields and potentials occurring 20 to 30 milliseconds after median nerve stimulation in human subjects were compared in order to investigate the sources of evoked potential components that have been attributed by different investigators to the thalamus or thalamocortical afferents, to separate radial sources in somatosensory cortex and motor cortex, or to a tangential source in somatosensory cortex. The magnetic and potential wave forms were highly similar in morphology, and their spatial distributions were centered over sensorimotor cortex, were dipolar in shape, and differed in orientation by approximately 90 degrees; distances between the minimum and maximum of the magnetic distributions were about 60 percent of those of the potential distributions. These results cannot be accounted for by thalamic sources or radial cortical sources alone, but are consistent with a tangential source in somatosensory cortex, with an additional smaller contribution from radial sources.  相似文献