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Nitrate labeled with (13)N ((13)NO(3)(-)) was produced in a cyclotron by the (16)O(p, alpha)(13)N reaction with protons having energies of 14.5 million electron volts. The (13)NO(3)(-) was used as a tracer for direct quantitative measurements of denitrification rates in soils from flooded rice fields. The (13)N technique provides a new tracer method for the measurement of denitrification rates in natural systems over short time intervals, without changing the concentration of NO(3)(-)in the system.  相似文献   
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Vesta's surface is characterized by abundant impact craters, some with preserved ejecta blankets, large troughs extending around the equatorial region, enigmatic dark material, and widespread mass wasting, but as yet an absence of volcanic features. Abundant steep slopes indicate that impact-generated surface regolith is underlain by bedrock. Dawn observations confirm the large impact basin (Rheasilvia) at Vesta's south pole and reveal evidence for an earlier, underlying large basin (Veneneia). Vesta's geology displays morphological features characteristic of the Moon and terrestrial planets as well as those of other asteroids, underscoring Vesta's unique role as a transitional solar system body.  相似文献   
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Four new pyrenocines, named pyrenocines J-M (1-4), were isolated from an endophytic fungus, Phomopsis sp, by a bioassay-guided method. The structures of the new compound have been assigned from 1H and 13C NMR spectra, DEPT, and by 2D COSY, HMQC, and HMBC experiments. Preliminary studied showed that compounds 1, 2 and 4 showed good antifungal, antibacterial, and algicidal properties, while compound 3 had good antibacterial and algicidal properties.  相似文献   
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Aging     
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An effective long‐term treatment is necessary for mares with pyometra, because the condition tends to recur. In many affected animals, several conformational or anatomical anomalies contribute to impaired uterine clearance. Ovariohysterectomy is the surgical procedure of choice. Conservative therapy consists of draining and flushing the uterus, and systemic anti‐inflammatory and antimicrobial treatment. Uterine secretions tend to accumulate again after local treatment, especially in mares with poor vaginal conformation or cervical adhesions. Herein, we describe three cases in which a cervical stent was used in mares after mechanical or manual dilation of the cervix to achieve permanent draining of the uterus. The mares remained symptom‐free for up to 6 years and exhibited good clinical progress and good performance in competitions. Potential complications of the procedure include loss of the stent and obstruction caused by viscous secretion. A cervical stent is a relatively easy and low‐cost option for the long‐term treatment of pyometra in mares, particularly in cases where excessive costs of surgery and risks of a general anaesthesia are to be avoided.  相似文献   
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