Haplotype frequencies based on eight polymorphic sites at the 3' untranslated region of the HLA-G gene in individuals from two different geographical regions of Brazil

The Brazilian population represents an admixture of native Amerindians, Portuguese settlers and Africans who were brought as slaves during the colonization period that began in the 16th century and was followed by waves of immigrations of Europeans and Asians in the 20th century. The contribution of these different ethnic groups to the constitution of Brazilian populations from different geographic regions is variable and, in addition to environmental factors, might act by determining different allele profiles among Brazilian populations from different regions. We studied polymorphic sites at the 3' untranslated region of the HLA-G gene in individuals from a Northeastern Brazilian region and compared them to our previously published data about a Southeastern Brazilian region, located at a distance of 2589 km. Our results showed that most polymorphic sites present a similar distribution in both populations, except for the lower frequency of the +3003C allele in the Northeastern population compared to the Southeastern population. Although differences in genotypic distribution were only significant for the +3003 locus (P = 0.0201), the diversity of haplotypes was distinct for each population. These results are important for casecontrol studies on the association of human leucocyte antigen-G polymorphism with disease and also in terms of the genetic structure of two distinct Brazilian populations.

No-pole condition in Landau gauge: Properties of the Gribov ghost form factor and a constraint on the 2d gluon propagator

We study general properties of the Landau-gauge Gribov ghost form factor sigma(p(2)) for SU(N-c) Yang-Mills theories in the d-dimensional case. We find a qualitatively different behavior for d = 3, 4 with respect to the d = 2 case. In particular, considering any (sufficiently regular) gluon propagator D(p(2)) and the one-loop-corrected ghost propagator, we prove in the 2d case that the function sigma(p(2)) blows up in the infrared limit p -> 0 as -D(0) ln(p(2)). Thus, for d = 2, the no-pole condition sigma(p(2)) < 1 (for p(2) > 0) can be satisfied only if the gluon propagator vanishes at zero momentum, that is, D(0) = 0. On the contrary, in d = 3 and 4, sigma(p(2)) is finite also if D(0) > 0. The same results are obtained by evaluating the ghost propagator G(p(2)) explicitly at one loop, using fitting forms for D(p(2)) that describe well the numerical data of the gluon propagator in two, three and four space-time dimensions in the SU(2) case. These evaluations also show that, if one considers the coupling constant g(2) as a free parameter, the ghost propagator admits a one-parameter family of behaviors (labeled by g(2)), in agreement with previous works by Boucaud et al. In this case the condition sigma(0) <= 1 implies g(2) <= g(c)(2), where g(c)(2) is a "critical" value. Moreover, a freelike ghost propagator in the infrared limit is obtained for any value of g(2) smaller than g(c)(2), while for g(2) = g(c)(2) one finds an infrared-enhanced ghost propagator. Finally, we analyze the Dyson-Schwinger equation for sigma(p(2)) and show that, for infrared-finite ghost-gluon vertices, one can bound the ghost form factor sigma(p(2)). Using these bounds we find again that only in the d = 2 case does one need to impose D(0) = 0 in order to satisfy the no-pole condition. The d = 2 result is also supported by an analysis of the Dyson-Schwinger equation using a spectral representation for the ghost propagator. Thus, if the no-pole condition is imposed, solving the d = 2 Dyson-Schwinger equations cannot lead to a massive behavior for the gluon propagator. These results apply to any Gribov copy inside the so-called first Gribov horizon; i.e., the 2d result D(0) = 0 is not affected by Gribov noise. These findings are also in agreement with lattice data.

THE ROLE OF TURBULENT MAGNETIC RECONNECTION IN THE FORMATION OF ROTATIONALLY SUPPORTED PROTOSTELLAR DISKS

The formation of protostellar disks out of molecular cloud cores is still not fully understood. Under ideal MHD conditions, the removal of angular momentum from the disk progenitor by the typically embedded magnetic field may prevent the formation of a rotationally supported disk during the main protostellar accretion phase of low-mass stars. This has been known as the magnetic braking problem and the most investigated mechanism to alleviate this problem and help remove the excess of magnetic flux during the star formation process, the so-called ambipolar diffusion (AD), has been shown to be not sufficient to weaken the magnetic braking at least at this stage of the disk formation. In this work, motivated by recent progress in the understanding of magnetic reconnection in turbulent environments, we appeal to the diffusion of magnetic field mediated by magnetic reconnection as an alternative mechanism for removing magnetic flux. We investigate numerically this mechanism during the later phases of the protostellar disk formation and show its high efficiency. By means of fully three-dimensional MHD simulations, we show that the diffusivity arising from turbulent magnetic reconnection is able to transport magnetic flux to the outskirts of the disk progenitor at timescales compatible with the collapse, allowing the formation of a rotationally supported disk around the protostar of dimensions similar to 100 AU, with a nearly Keplerian profile in the early accretion phase. Since MHD turbulence is expected to be present in protostellar disks, this is a natural mechanism for removing magnetic flux excess and allowing the formation of these disks. This mechanism dismisses the necessity of postulating a hypothetical increase of the ohmic resistivity as discussed in the literature. Together with our earlier work which showed that magnetic flux removal from molecular cloud cores is very efficient, this work calls for reconsidering the relative role of AD in the processes of star and planet formation.

Residual stresses in Y-TZP crowns due to changes in the thermal contraction coefficient of veneers

Objective. To test the hypothesis that the difference in the coefficient of thermal contraction of the veneering porcelain above (˛liquid) and below (˛solid) its Tg plays an important role in stress development during a fast cooling protocol of Y-TZP crowns. Methods. Three-dimensional finite element models of veneered Y-TZP crowns were developed. Heat transfer analyses were conducted with two cooling protocols: slow (group A) and fast (groups B–F). Calculated temperatures as a function of time were used to determine the thermal stresses. Porcelain ˛solid was kept constant while its ˛liquid was varied, creating different ˛/˛solid conditions: 0, 1, 1.5, 2 and 3 (groups B–F, respectively). Maximum ( 1) and minimum ( 3) residual principal stress distributions in the porcelain layer were compared. Results. For the slowly cooled crown, positive 1 were observed in the porcelain, orientated perpendicular to the core–veneer interface (“radial” orientation). Simultaneously, negative 3 were observed within the porcelain, mostly in a hoop orientation (“hoop–arch”). For rapidly cooled crowns, stress patterns varied depending on ˛/˛solid ratios. For groups B and C, the patterns were similar to those found in group A for 1 (“radial”) and 3 (“hoop–arch”). For groups D–F, stress distribution changed significantly, with 1 forming a “hoop-arch” pattern while 3 developed a “radial” pattern. Significance. Hoop tensile stresses generated in the veneering layer during fast cooling protocols due to porcelain high ˛/˛solid ratio will facilitate flaw propagation from the surface toward the core, which negatively affects the potential clinical longevity of a crown.

Morphometric analysis of the placenta in the New World mouse Necromys lasiurus (Rodentia, Cricetidae): a comparison of placental development in cricetids and murids

Background: Stereology is an established method to extrapolate three-dimensional quantities from two-dimensional images. It was applied to placentation in the mouse, but not yet for other rodents. Herein, we provide the first study on quantitative placental development in a sigmodontine rodent species with relatively similar gestational time. Placental structure was also compared to the mouse, in order to evaluate similarities and differences in developmental patterns at the end of gestation. Methods: Fetal and placental tissues of Necromys lasiurus were collected and weighed at 3 different stages of gestation (early, mid and late gestation) for placental stereology. The total and relative volumes of placenta and of its main layers were investigated. Volume fractions of labyrinth components were quantified by the One Stop method in 31 placentae collected from different individuals, using the Mercator® software. Data generated at the end of gestation from N. lasiurus placentae were compared to those of Mus musculus domesticus obtained at the same stage. Results: A significant increase in the total absolute volumes of the placenta and its main layers occurred from early to mid-gestation, followed by a reduction near term, with the labyrinth layer becoming the most prominent area. Moreover, at the end of gestation, the total volume of the mouse placenta was significantly increased compared to that of N. lasiurus although the proportions of the labyrinth layer and junctional zones were similar. Analysis of the volume fractions of the components in the labyrinth indicated a significant increase in fetal vessels and sinusoidal giant cells, a decrease in labyrinthine trophoblast whereas the proportion of maternal blood space remained stable in the course of gestation. On the other hand, in the mouse, volume fractions of fetal vessels and sinusoidal giant cells decreased whereas the volume fraction of labyrinthine trophoblast increased compared to N. lasiurus placenta. Conclusions: Placental development differed between N. lasiurus and M. musculus domesticus. In particular, the low placental efficiency in N. lasiurus seemed to induce morphological optimization of fetomaternal exchanges. In conclusion, despite similar structural aspects of placentation in these species, the quantitative dynamics showed important differences.

Interspecific variation of the bacterial community structure in the phyllosphere of the three major plant components of mangrove forests

Mangrove forests encompass a group of trees species that inhabit the intertidal zones, where soil is characterized by the high salinity and low availability of oxygen. The phyllosphere of these trees represent the habitat provided on the aboveground parts of plants, supporting in a global scale, a large and complex microbial community. The structure of phyllosphere communities reflects immigration, survival and growth of microbial colonizers, which is influenced by numerous environmental factors in addition to leaf physical and chemical properties. Here, a combination of culture-base methods with PCR-DGGE was applied to test whether local or plant specific factors shape the bacterial community of the phyllosphere from three plant species (Avicenia shaueriana, Laguncularia racemosa and Rhizophora mangle), found in two mangroves. The number of bacteria in the phyllosphere of these plants varied between 3.62 x 10(4) in A. schaeriana and 6.26 x 10³ in R. mangle. The results obtained by PCR-DGGE and isolation approaches were congruent and demonstrated that each plant species harbor specific bacterial communities in their leaves surfaces. Moreover, the ordination of environmental factors (mangrove and plant species), by redundancy analysis (RDA), also indicated that the selection exerted by plant species is higher than mangrove location on bacterial communities at phyllosphere.

Segue 3: the youngest globular cluster in the outer halo

Deep Galileo (Telescopio Nazionale Galileo) B, V and I images of Segue 3, reaching V ∼ 25, reveal that it is the youngest globular cluster known so far in the Galaxy. A young age of 3.2 Gyr is found, differently from a previous estimate of 12 Gyr. It also appears to be moderately metal rich with [Fe/H] ∼ −0.8, rather than [Fe/H] ∼ −1.7, as previously suggested by Fadely et al. A main difference in the age derivation relative to Fadely et al. comes from the consideration of subgiant branch stars in the isochrone fitting. A deduced distance of d⊙ = 29.1 kpc is compatible with the outer halo location of other low luminosity globular clusters.

Modulation of plasma levels and percentages of incorporation of ω-3 PUFAs in egg yolk under the influence of supplementation sources rich in omega 3 to diet of laying

Hundred forty-four Shaver White laying hens were used over a 4 week experimental period to investigate the effect of 3% of soybean oil, corn oil (MIL), canola oil, flaxseed oil (LIN), salmon oil (SAL) or tuna and sardine oil (SR/AT) added to the diets, upon the fatty acid egg yolk composition, blood plasma levels and incorporation time of each fatty acid into the egg yolk. Hens were allocated into 72 cages and the experimental design was a 6 x 6 randomized factorial model. Hens fed 3% of different oils, responded with increased polyunsaturated fatty acids omega 3 (ω-3 PUFAs), except for corn oil. The addition of flaxseed, soybean or corn oil into the diet increased the PUFAs levels into the egg yolk and in the blood plasma. Adding tuna and sardine oil into the diet increased the concentration of yolk saturated fatty acids. The levels of ω-3 PUFAs were increased in the tuna and sardine oil treatment, while the flaxseed oil increased the plasma fatty acids. The deposition of 349.28 mg/yolk of a-linolenic fatty acids (ALA) was higher in the group fed LIN, while the higher equal to 157.13 mg DHA/yolk was observed in group SR/AT. In the plasma, deposition increased from 0.33% (MIL) for 6.29% ALA (LIN), while that of DHA increase of 0.47% (MIL) for 4.24% (SAL) and 4.48% (SR/AT) and of 0.98% (MIL) for 6.14% (SR/AT) and 8.44% (LIN) of ω-3 PUFAs. The percentage of EPA into the yolk and plasma was higher for the hens fed 3% tuna and sardine oil diet, as well as the levels of yolk DHA. The concentration of DHA into the plasma was higher for the salmon and tuna/sardine oil treatments. The PUFAs yolk decreased during the first eight days of experiment, while the ω-3 PUFAs increased during the same period. The concentration of ALA increased until ten days of experiment, while the percentage of EPA and DHA increased up to the eighth experimental day

Lipid profile of the yolk under the influence of supplementaries sources rich in Ω-3 PUFAs in the diet of laying hens in the time

Two hundred eighty-eight 32-wk-old Hisex White laying hens were used in this research during a 10 weeks period, arranged in a 2 x 5 completely randomized factorial design, with three replicates of eight birds per treatment. Two groups: fish oil (OP) and Marine Algae (AM) with five DHA levels (120, 180, 240, 300 and 360 mg/100 g diet) were assigned including two control groups birds fed corn and soybean basal diet (CON) and a diet supplemented with AM (AM420) to study the effect of time 0, 2, 4, 6 and 8 weeks (wk) on the efficiency of egg yolk fatty acid enrichment. The means varied (p<0.01) of 17.63% (OP360) to 22.08% (AM420) is the total Polyunsaturated Fatty Acids (PUFAs) and 45.8 mg/g (OP360), 40.37 mg/g (OP360, 4 wk) to 65.82 mg/g (AM420) and 68.79 mg/g/yolk (AM120, 8 wk) for n-6 PUFAs. On the influence of sources and levels in the times, the means of n-3 PUFAs increased by 5.58 mg/g (AM120, 2 wk) to 14.16 mg/g (OP360, 6 wk) when compared to average of 3.34 mg PUFAs Ω/g/yolk (CON). Usually, the means DHA also increased from 22.34 (CON) to 176.53 mg (μ, OP360), 187.91 mg (OP360, 8 wk) and 192.96 mg (OP360, 6 wk) and 134.18 mg (μ, OP360), 135.79 mg (AM420, 6 wk), 149.75 mg DHA (AM420, 8 wk) per yolk. The opposite was observed for the means AA, so the effect of the sources, levels and times, decreased (P <0.01) of 99.83 mg (CON) to 31.99 mg (OP360, 4 wk), 40.43 mg (μ, OP360) to 61.21 mg (AM420) and 71.51 mg AA / yolk (μ, AM420). Variations of the average weight of 15.75g (OP360) to 17.08g (AM420) yolks of eggs de 32.55% (AM420) to 34.08% (OP360) of total lipids and 5.28 g (AM240) to 5.84 g (AM120) of fat in the yolk were not affected (p>0.05) by treatments, sources, levels and times studied. Starting of 2 week, the hens increased the level of n-3 PUFAs in the egg yolks, being expressively increased (p<0.01) until 4 weeks, which after the increased levels of n-3 PUFAs tended to if stabilize around of time of 8 experimental weeks, when it was more effective saturation of the tissues and yolk.

Experimental and numerical analysis of dry contact in the pin on disc test

The reduction of friction and wear in systems presenting metal-to-metal contacts, as in several mechanical components, represents a traditional challenge in tribology. In this context, this work presents a computational study based on the linear Archard's wear law and finite element modeling (FEM), in order to analyze unlubricated sliding wear observed in typical pin on disc tests. Such modeling was developed using finite element software Abaqus® with 3-D deformable geometries and elastic–plastic material behavior for the contact surfaces. Archard's wear model was implemented into a FORTRAN user subroutine (UMESHMOTION) in order to describe sliding wear. Modeling of debris and oxide formation mechanisms was taken into account by the use of a global wear coefficient obtained from experimental measurements. Such implementation considers an incremental computation for surface wear based on the nodal displacements by means of adaptive mesh tools that rearrange local nodal positions. In this way, the worn track was obtained and new surface profile is integrated for mass loss assessments. This work also presents experimental pin on disc tests with AISI 4140 pins on rotating AISI H13 discs with normal loads of 10, 35, 70 and 140 N, which represent, respectively, mild, transition and severe wear regimes, at sliding speed of 0.1 m/s. Numerical and experimental results were compared in terms of wear rate and friction coefficient. Furthermore, in the numerical simulation the stress field distribution and changes in the surface profile across the worn track of the disc were analyzed. The applied numerical formulation has shown to be more appropriate to predict mild wear regime than severe regime, especially due to the shorter running-in period observed in lower loads that characterizes this kind of regime.

Dynamical aspects of atmospheric data assimilation in the tropics

A faithful depiction of the tropical atmosphere requires three-dimensional sets of observations. Despite the increasing amount of observations presently available, these will hardly ever encompass the entire atmosphere and, in addition, observations have errors. Additional (background) information will always be required to complete the picture. Valuable added information comes from the physical laws governing the flow, usually mediated via a numerical weather prediction (NWP) model. These models are, however, never going to be error-free, why a reliable estimate of their errors poses a real challenge since the whole truth will never be within our grasp. The present thesis addresses the question of improving the analysis procedures for NWP in the tropics. Improvements are sought by addressing the following issues: - the efficiency of the internal model adjustment, - the potential of the reliable background-error information, as compared to observations, - the impact of a new, space-borne line-of-sight wind measurements, and - the usefulness of multivariate relationships for data assimilation in the tropics. Most NWP assimilation schemes are effectively univariate near the equator. In this thesis, a multivariate formulation of the variational data assimilation in the tropics has been developed. The proposed background-error model supports the mass-wind coupling based on convectively-coupled equatorial waves. The resulting assimilation model produces balanced analysis increments and hereby increases the efficiency of all types of observations. Idealized adjustment and multivariate analysis experiments highlight the importance of direct wind measurements in the tropics. In particular, the presented results confirm the superiority of wind observations compared to mass data, in spite of the exact multivariate relationships available from the background information. The internal model adjustment is also more efficient for wind observations than for mass data. In accordance with these findings, new satellite wind observations are expected to contribute towards the improvement of NWP and climate modeling in the tropics. Although incomplete, the new wind-field information has the potential to reduce uncertainties in the tropical dynamical fields, if used together with the existing satellite mass-field measurements. The results obtained by applying the new background-error representation to the tropical short-range forecast errors of a state-of-art NWP model suggest that achieving useful tropical multivariate relationships may be feasible within an operational NWP environment.

Three-dimensional CT reconstruction: other tool to teach in the veterinary colleges

[ES]The purpose of this paper was to use threedimensional computed tomographic reconstruction as another tool to teach in the veterinary colleges. 2-millimeters thick transverse images of two foals and one dog were obtained. Images provided excellent detail of relevant anatomic structures and detailed information regarding the extent of disease and accurate discrimination of neoplastic versus non-neoplastic diseases. Tridimensional reconstruction can be a valuable diagnostic aid for clinical evaluation of several disturbances and could be used as a tool for teaching anatomy in veterinary schools.

New functional and biomechanical assessments for the improvement of the surgical navigation systems for joint replacement in the human lower limb

In case of severe osteoarthritis at the knee causing pain, deformity, and loss of stability and mobility, the clinicians consider that the substitution of these surfaces by means of joint prostheses. The objectives to be pursued by this surgery are: complete pain elimination, restoration of the normal physiological mobility and joint stability, correction of all deformities and, thus, of limping. The knee surgical navigation systems have bee developed in computer-aided surgery in order to improve the surgical final outcome in total knee arthroplasty. These systems provide the surgeon with quantitative and real-time information about each surgical action, like bone cut executions and prosthesis component alignment, by mean of tracking tools rigidly fixed onto the femur and the tibia. Nevertheless, there is still a margin of error due to the incorrect surgical procedures and to the still limited number of kinematic information provided by the current systems. Particularly, patello-femoral joint kinematics is not considered in knee surgical navigation. It is also unclear and, thus, a source of misunderstanding, what the most appropriate methodology is to study the patellar motion. In addition, also the knee ligamentous apparatus is superficially considered in navigated total knee arthroplasty, without taking into account how their physiological behavior is altered by this surgery. The aim of the present research work was to provide new functional and biomechanical assessments for the improvement of the surgical navigation systems for joint replacement in the human lower limb. This was mainly realized by means of the identification and development of new techniques that allow a thorough comprehension of the functioning of the knee joint, with particular attention to the patello-femoral joint and to the main knee soft tissues. A knee surgical navigation system with active markers was used in all research activities presented in this research work. Particularly, preliminary test were performed in order to assess the system accuracy and the robustness of a number of navigation procedures. Four studies were performed in-vivo on patients requiring total knee arthroplasty and randomly implanted by means of traditional and navigated procedures in order to check for the real efficacy of the latter with respect to the former. In order to cope with assessment of patello-femoral joint kinematics in the intact and replaced knees, twenty in-vitro tests were performed by using a prototypal tracking tool also for the patella. In addition to standard anatomical and articular recommendations, original proposals for defining the patellar anatomical-based reference frame and for studying the patello-femoral joint kinematics were reported and used in these tests. These definitions were applied to two further in-vitro tests in which, for the first time, also the implant of patellar component insert was fully navigated. In addition, an original technique to analyze the main knee soft tissues by means of anatomical-based fiber mappings was also reported and used in the same tests. The preliminary instrumental tests revealed a system accuracy within the millimeter and a good inter- and intra-observer repeatability in defining all anatomical reference frames. In in-vivo studies, the general alignments of femoral and tibial prosthesis components and of the lower limb mechanical axis, as measured on radiographs, was more satisfactory, i.e. within ±3°, in those patient in which total knee arthroplasty was performed by navigated procedures. As for in-vitro tests, consistent patello-femoral joint kinematic patterns were observed over specimens throughout the knee flexion arc. Generally, the physiological intact knee patellar motion was not restored after the implant. This restoration was successfully achieved in the two further tests where all component implants, included the patellar insert, were fully navigated, i.e. by means of intra-operative assessment of also patellar component positioning and general tibio-femoral and patello-femoral joint assessment. The tests for assessing the behavior of the main knee ligaments revealed the complexity of the latter and the different functional roles played by the several sub-bundles compounding each ligament. Also in this case, total knee arthroplasty altered the physiological behavior of these knee soft tissues. These results reveal in-vitro the relevance and the feasibility of the applications of new techniques for accurate knee soft tissues monitoring, patellar tracking assessment and navigated patellar resurfacing intra-operatively in the contest of the most modern operative techniques. This present research work gives a contribution to the much controversial knowledge on the normal and replaced of knee kinematics by testing the reported new methodologies. The consistence of these results provides fundamental information for the comprehension and improvements of knee orthopedic treatments. In the future, the reported new techniques can be safely applied in-vivo and also adopted in other joint replacements.

Computer simulation of ordering and dynamics in liquid crystals in the bulk and close to the surface

The aim of this PhD thesis is to investigate the orientational and dynamical properties of liquid crystalline systems, at molecular level and using atomistic computer simulations, to reach a better understanding of material behavior from a microscopic point view. In perspective this should allow to clarify the relation between the micro and macroscopic properties with the objective of predicting or confirming experimental results on these systems. In this context, we developed four different lines of work in the thesis. The first one concerns the orientational order and alignment mechanism of rigid solutes of small dimensions dissolved in a nematic phase formed by the 4-pentyl,4 cyanobiphenyl (5CB) nematic liquid crystal. The orientational distribution of solutes have been obtained with Molecular Dynamics Simulation (MD) and have been compared with experimental data reported in literature. we have also verified the agreement between order parameters and dipolar coupling values measured in NMR experiments. The MD determined effective orientational potentials have been compared with the predictions of Maier­Saupe and Surface tensor models. The second line concerns the development of a correct parametrization able to reproduce the phase transition properties of a prototype of the oligothiophene semiconductor family: sexithiophene (T6). T6 forms two crystalline polymorphs largely studied, and possesses liquid crystalline phases still not well characterized, From simulations we detected a phase transition from crystal to liquid crystal at about 580 K, in agreement with available experiments, and in particular we found two LC phases, smectic and nematic. The crystal­smectic transition is associated to a relevant density variation and to strong conformational changes of T6, namely the molecules in the liquid crystal phase easily assume a bent shape, deviating from the planar structure typical of the crystal. The third line explores a new approach for calculating the viscosity in a nematic through a virtual exper- iment resembling the classical falling sphere experiment. The falling sphere is replaced by an hydrogenated silicon nanoparticle of spherical shape suspended in 5CB, and gravity effects are replaced by a constant force applied to the nanoparticle in a selected direction. Once the nanoparticle reaches a constant velocity, the viscosity of the medium can be evaluated using Stokes' law. With this method we successfully reproduced experimental viscosities and viscosity anisotropy for the solvent 5CB. The last line deals with the study of order induction on nematic molecules by an hydrogenated silicon surface. Gaining predicting power for the anchoring behavior of liquid crystals at surfaces will be a very desirable capability, as many properties related to devices depend on molecular organization close to surfaces. Here we studied, by means of atomistic MD simulations, the flat interface between an hydrogenated (001) silicon surface in contact with a sample of 5CB molecules. We found a planar anchoring of the first layers of 5CB where surface interactions are dominating with respect to the mesogen intermolecular interactions. We also analyzed the interface 5CB­vacuum, finding a homeotropic orientation of the nematic at this interface.