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We describe a robust and efficient chain-of-states method for computing Minimum Energy Paths (MEPs) associated to barrier-crossing events in poly-atomic systems, which we call the acceleration method. The path is parametrized in terms of a continuous variable t ∈ [0,1] that plays the role of time. In contrast to previous chain-of-states algorithms such as the nudged elastic band or string methods, where the positions of the states in the chain are taken as variational parameters in the search for the MEP, our strategy is to formulate the problem in terms of the second derivatives of the coordinates with respect to t, i.e., the state accelerations. We show this to result in a very simple and efficient method for determining the MEP. We describe the application of the method to a series of test cases, including two low-dimensional problems and the Stone-Wales transformation in C60. [ABSTRACT FROM AUTHOR]

We present the implementation of a fast real-space algorithm for density functional calculations for atomic nanoclusters. The numerical method is based on a fourth-order operator splitting technique for the solution of the Kohn-Sham equation [1]. The convergence of the procedure is about one order of magnitude better than that of previously used second-order operator factorizations. The method has now been extended to deal with non-local pseudopotentials of the Kleinman-Bylander [2] type, permitting calculations for realistic systems, without significantly degrading the convergence rate. We demonstrate the convergence of the method for the examples C and C60 and present examples of structure calculations of Na and Mg clusters. [ABSTRACT FROM AUTHOR]

The high need for root canal treatments in different dental groups continues to be a challenge for professionals; since, it is necessary the knowledge of the techniques, materials, equipment and instruments, as well as of the anatomical variants on which the success or failure depends. Anatomical variations include the presence of a second root canal in lower incisors (SCRII). The present investigation is of a literature review type, articles of the type were included: literature review and descriptive studies, papers in English and Spanish were included; the search was carried out between the months of January and July 2021, in the following databases: Hinari, EBSCO host, Pubmed. The results indicate that the incidence of finding two canals in both lower incisors range from 2% to 77.9%; individually in lower central incisors the prevalence is from 11.90% to 32.50% and in lower lateral incisors, it is found between 17.50% and 58% of cases. The location of the SCRII entrance has been the subject of multiple studies, finding that there is no consensus on this point; since similar percentages have been described among the different thirds (cervical, middle and apical), an influencing factor could be ethnicity. Cone beam computed tomography has gained ground over conventional radiography and the use of magnification as the most effective diagnostic technique; however, it is suggested to carry out a study with Salvadoran patients to obtain a value that guides professionals and thus avoid endodontic treatment failures in said teeth. [ABSTRACT FROM AUTHOR]

The problem of two-dimensional, independent electrons subject to a periodic potential and a uniform perpendicular magnetic field unveils surprisingly rich physics, as epitomized by the fractal energy spectrum known as Hofstadter's butterfly. It has hitherto been addressed using various approximations rooted in either the strong potential or the strong field limiting cases. Here, we report calculations of the full spectrum of the single-particle Schrödinger equation without further approximations. Our method is exact, up to numerical precision, for any combination of potential and uniform field strength. We first study a situation that corresponds to the strong potential limit, and compare the exact results to the predictions of a Hofstadter-like model. We then go on to analyze the evolution of the fractal spectrum from a Landau-like nearly free electron system to the Hofstadter tight-binding limit by tuning the amplitude of the modulation potential. [ABSTRACT FROM AUTHOR]

In this work, the scaling behavior of the sleep process is evaluated by using detrended fluctuation analysis based on wavelets. The analysis is carried out from arrivals of short and recurrent cortical events called A-phases, which in turn build up the Cyclic Alternating Pattern phenomenon, and are classified in three types: A1, A2 and A3. In this study, 61 sleep recordings corresponding to healthy, nocturnal frontal lobe epilepsy patients and sleep-state misperception subjects, were analyzed. From the A-phase annotations, the onsets were extracted and a binary sequence with one second resolution was generated. An item in the sequence has a value of one if an A-phase onset occurs in the corresponding window, and a value of zero otherwise. In addition, we consider other different temporal resolutions from 2 s to 256 s. Furthermore, the same analysis was carried out for sequences obtained from the different types of A-phases and their combinations. The results of the numerical analysis showed a relationship between the time resolutions and the scaling exponents; specifically, for higher time resolutions a white noise behavior is observed, whereas for lower time resolutions a behavior towards to 1 / f -noise is exhibited. Statistical differences among groups were observed by applying various wavelet functions from the Daubechies family and choosing the appropriate sequence of A-phase onsets. This scaling analysis allows the characterization of the free-scale dynamic of the sleep process that is specific for each sleep condition. The scaling exponent could be useful as a diagnosis parameter in clinics when sleep macrostructure does not offer enough information. [ABSTRACT FROM AUTHOR]

The path integral formulation has been combined with several methods to determine free energies of quantum many-body systems, such as adiabatic switching and reversible scaling. These techniques are alternatives to the standard thermodynamic integration method. A quantum Einstein crystal is used as a model to demonstrate the accuracy and reliability of these free energy methods in quantum simulations. Our main interest focuses on the calculation of the melting temperature of Ne at ambient pressure, taking into account quantum effects in the atomic dynamics. The free energy of the solid was calculated by considering a quantum Einstein crystal as reference state, while for the liquid, the reference state was defined by the classical limit of the fluid. Our findings indicate that, while quantum effects in the melting temperature of this system are small, they still amount to about 6% of the melting temperature, and are therefore not negligible. The particle density as well as the melting enthalpy and entropy of the solid and liquid phases at coexistence is compared to results obtained in the classical limit and also to available experimental data. [ABSTRACT FROM AUTHOR]

We consider the problem of how a condensed molecular system approaches equilibrium, focusing on the particular case of water. We show, by means of extensive molecular dynamics simulations, that the existence of different types of degrees of freedom affects the dynamics of equilibration, and this influence is made most obvious in the system's temperature. When equipartition of energy does not hold in the initial, nonequilibrium state, the instantaneous temperature can be up to a few degrees lower than that observed under equipartition conditions, resulting in a Mpemba-like effect. Though our study considers water in particular, our findings apply more generally to condensed molecular systems. [ABSTRACT FROM AUTHOR]

Saturated and trans fatty acids have been associated with the risk to develop cardiovascular diseases. However, health-promoting effects are associated with consumption of anhydrous milk fat (AMF) and ruminant trans fatty acids, such as conjugated linoleic acid (CLA) and vaccenic acid (VA) contained in the lipid fraction of milk and dairy products. The purpose of this study was to evaluate the effect of AMF naturally enriched with CLA and VA in spontaneously hypertensive rats (SHR), using sterculic oil to inhibit the conversion of VA into CLA. The administration of AMF to SHR during 7 weeks exerted beneficial effects on cardiovascular risk biomarkers (reduction of insulin, blood lipids, increase of adiponectin). When sterculic oil was included, some parameters were further ameliorated (reduction of insulin, increase of adiponectin). Sterculic oil alone reduced body weight and adiposity, and improved blood pressure, adiponectin and triglyceride levels. [ABSTRACT FROM AUTHOR]

Background: We aimed to assess the efficacy of a GnRH antagonist in intrauterine insemination (IUI) cycles to increase number of mature ovulatory follicles and pregnancy rates.Methods: Prospective randomized study. Women (18-38 years old) with primary/secondary infertility were included. Eighty-two patients were randomly assigned to controlled ovarian stimulation (COS) consisting of rFSH + GnRH antagonist or rFSH alone.Results: A non-significant increase in the total amount of rFSH was seen in the GnRH antagonist group (707+/-240 IU) with respect to the control group (657+/-194 IU). The number of mature follicles (> or =16 mm) was significantly higher in the GnRH antagonist group than in the control group (2.4+/-1.4 versus 1.7+/-1.2, P<0.05). Pregnancy rates were significantly increased in the group of patients receiving the GnRH antagonist (38%) compared to the control group (14%). The only non-single pregnancy (triplets) occurred in the antagonist group.Conclusions: In this preliminary study, adding the GnRH antagonist to the COS protocol for IUI cycles significantly increased pregnancy rates. Nevertheless, these results may not be associated directly with the antagonist itself but with the fact that more mature ovulatory follicles are present by the day of the hCG. Finally, the risk for multiple gestations needs to be carefully evaluated. [ABSTRACT FROM AUTHOR]

Objective: After tubal ligation, normal bone mass in the presence of gonadal deficit has been reported. These incongruent results motivated us to examine the topic. Study design: Bone mass was assessed by densitometry and ultrasonography 60 days after surgery on 100-day-old female Wistar rats. Fifteen Wistar rats with uterine horn ligation (TL) were compared with 15 unoperated, 15 with a sham uterine horn ligation (Sham-TL), and 15 ovariectomized (OVX), using ANOVA and a correlation test to determine the relations between results. Results: Femoral and vertebral bone mass were significantly lower in the OVX y TL groups than in unoperated and controls groups (P<0.0001). Conclusions: Our study revealed significantly lower axial and peripheral bone mass in rats with uterine horn ligation. [Copyright &y& Elsevier]

Abstract Background A study was carried out over a 24-month interval to determine if an initial measurement of serum tartrate-resistant acid phosphatase would be predictive of bone mass loss quantified by dual-energy X-ray absorptiometry, as total bone mineral content and total bone mineral content corrected for weight. Design Sixty-two women were studied (at onset: mean age 59·7 ± 8·9 years, 10·8 ± 8·8 years since menopause; at conclusion: mean age 61·9 ± 8·8 and 13·0 ± 8·7 since menopause). Results A paired Wilcoxon test showed a small, but significant, increase in weight (P < 0·05) and decrease in height (P < 0·05). Total bone mineral content and total bone mineral content corrected for weight decreased (P < 0·005 and 0·0001, respectively). Serum tartrate-resistant acid phosphatase increased (P < 0·005). Single-regression analysis showed that the per cent bone mass loss observed between the first and second body bone mineral content measurements correlated negatively with the first serum tartrate-resistant acid phosphatase determination (r = -0·62, P < 0·0001). Changes in tartrate-resistant acid phosphatase correlated negatively with changes in total bone mineral content (r = -0·79, P < 0·0001). In a multiple regression analysis of per cent change in bone mass against initially important variables such as age, years since menopause, weight, and tartrate-resistant acid phosphatase, only tartrate-resistant acid phosphatase was significant (P < 0·0001). The sensitivity and specifity of tartrate-resistant acid phosphatase for evaluating bone loss were 86% and 78%, respectively, and the area under the curve was of 0·83 (95% CI 0·71–0·95). Conclusion These results show that a simple measurement of serum tartrate-resistant acid phosphatase can help to predict the potential rate of bone mass loss in women. [ABSTRACT FROM AUTHOR]

We report the first study on the thermal behavior of the stiffness of individual carbon nanotubes, which is achieved by measuring the resonance frequency of their fundamental mechanical bending modes. We observe a reduction of the Young's modulus over a large temperature range with a slope -(173±65) ppm/K in its relative shift. These findings are reproduced by two different theoretical models based on the thermal dynamics of the lattice. These results reveal how the measured fundamental bending modes depend on the phonons in the nanotube via the Young's modulus. An alternative description based on the coupling between the measured mechanical modes and the phonon thermal bath in the Akhiezer limit is discussed. [ABSTRACT FROM AUTHOR]

Presents a correction to the article "LH Improves Early Follicular Recruitment in Women Over 38 Years Old" that was published in the 2005 issue.