Water Use and Growth in Three Populations of Red Cedar （Cedrela odorata L.） and Associated Crops in Mexico

The association between the growth and water-use efficiency in three populations of C. odorata in Veracruz Mexico （La Antigua, Misantla and Catemaco） from two agroforestry system sites was studied, one in association with corn and another with pipiain. TRP （transpiration）, gs （stomatal conductivity）, CO2A （CO2 assimilation）, WUE （water use efficiency）, height, coverage and stem diameter were measured. The populafon of La Antigua associated with pipian presented the highest WUE （7.13 μmol CO2 m2-sl/mmol H20 m2.sl）, while the population of Catemaco reached high values （10 μmol CO2 m2 sl/mmol H20 m2-s1） in the site associated with corn, the populations established with corn presented a great growth in height and stem diameter. Based on the physiological responses and growth of the studied populations, the towns of La Antigua and Catemaco may be recommended for the establishment of commercial plantations.

Melatonin as an antioxidant preserving sperm from domestic animals

The role of melatonin on sperm function as well as its use as antioxidant for sperm conservation is analysed in this review. Melatonin has been included in the cooling/freezing media for the conservation of spermatozoa. Depending on the animal species, the best dose to improve sperm quality and fertile capacity is in the range from 0.01 mM to 3.00 mM. Since the work started on the use of melatonin as antioxidant for the conservation of spermatozoa (2011), a search for references was done on the subject using internet and our university libraries: journals, proceedings, thesis,etc. The search focused on animal spermatozoa, but a collection of papers on human spermatozoa was also carried out.

Susceptibility to gravitational processes due to land cover change in the Río Chiquito-Barranca del Muerto subbasin(Pico De Orizaba Volcano, México)

instability associated Land cover change can lead to slope by accelerating erosive processes with agriculture, forestry, and infrastructure. The Rio Chiquito-Barranca del Muerto subbasin has experienced an increase in land cover change due to government programs and the establishment of agricultural and urban areas. The aim of this study was to provide a model to map the susceptibility to gravitational processes along sites where anthropogenic land cover change has occurred. The method was based on the stratification of the subbasin according to landforms and cartographic variables. These variables were used in a multi- criteria assessment to assign weights according to their contribution to the onset of new gravitationalprocesses. Those weights were used to create a susceptibility map based on a weighted linear sum. The accuracy of the resulting map was validated in an error matrix with a random stratified design based on susceptibility classes per landform. The results produced a map of areas with susceptibility to gravitational processes due to land cover change; this susceptibility is very high in the undifferentiated pyroclastic slope and limestone mountain, where it derives not only from anthropogenie effects on natural vegetation cover, but also from steep slopes, weathered materials, low apparent density, high erosivity, and previous gravitational processes. The results support other studies that concluded that loss of vegetation is a triggering factor in the formation of gravitational processes, but also show that excessive reforestation can increase gravitational processes.

Hamiltonian Characterization for Dipolar Coupled Spin Systems

Measuring the Hamiltonian of dipolar coupled spin systems is usually a difficult task due to the high complexity of their spectra. Currently, molecules with unknown geometrical structure and low symmetry are extremely tedious or impossible to analyze by sheer spectral fitting. We present a novel method that addresses the problem of spectral analysis and report experimental results of extracting, by spectral fitting, the parameters of an oriented 6-spin system with very low symmetry in structure, without using apriori knowledge or assumptions on the molecular geometry or order parameters. The advantages of our method are achieved with the use of a new spectral analysis algorithm non-assigned frequency optimization of NMR spectra （NAFONS） and by the use of simplified spectra obtained by transition selective pulses. This new method goes beyond the limit of spectral analysis for dipolar coupled spin systems and is helpful for related fields, such as quantum computation and molecular structure analysis.