Quantum simulations of neutral water clusters and singly-charged water cluster anions.

We report a computational study of the structural and energetic properties of water clusters and singly-charged water cluster anions containing from 20 to 573 water molecules. We have used both a classical and a quantum description of the molecular degrees of freedom. Water intra and inter-molecular interactions have been modelled through the SPC/F model, while the water-excess electron interaction has been described via the well-known Turi-Borgis potential. We find that in general the quantum effects of the water degrees of freedom are small, but they do influence the cluster-size at which the excess electron stabilises inside the cluster, which occurs at smaller cluster sizes when quantum effects are taken into consideration.

Interrelation of Elasticity and Thermal Bath in Nanotube Cantilevers.

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.

Paths towards equilibrium in molecular systems: The case of water.

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.

Prevalence of esophageal inlet patch and clinical characteristics of the patients. / Prevalencia y características clínicas de pacientes con parche de mucosa gástrica ectópica en esófago.

INTRODUCTION AND AIMS: An inlet patch (IP) is the presence of gastric columnar epithelium outside of the stomach. No studies have been conducted in Mexico on that pathology. The aim of the present study was to determine the prevalence of esophageal IP and the clinical characteristics of the patients that present it. MATERIALS AND METHODS: A cross-sectional study was conducted that included consecutive patients referred for endoscopy within the time frame of September 2015 to May 2016. The patients answered a questionnaire, and high-definition endoscopy with digital chromoendoscopy was performed. The prevalence of IP was identified. The chi-square test was used to compare the clinical characteristics between patients that presented with esophageal IP and those without it. RESULTS: A total of 239 patients were included in the study. Their mean age was 53 years, and 130 (54.4%) were women. IP was found in 26 patients (10.9%), 15 of whom were men (57.7%). The main reason for referral to endoscopy was gastroesophageal reflux disease, present in 69.2% of the patients with IP and in 55.9% without IP (p=.19). The most common symptoms were heartburn and regurgitation. The former was present in 69.2% of the patients with IP and in 59.1% without IP (p=.32), and the latter was present in 65.4% of the patients with IP and 69.1% without IP (p=.7). Extraesophageal manifestation distribution was: cough in 46.2% of the patients with IP and 38% without IP (p=.45) and dysphonia in 54% with IP and 47% without IP (p=.53). Twenty-three percent of the patients with IP had Barrett's esophagus, as did 23% without IP (p=.99). CONCLUSIONS: The prevalence of IP was high. The primary referral diagnosis was gastroesophageal reflux disease. No differences were found in relation to symptoms or the presence of Barrett's esophagus between the patients with and without IP.

Risk factors associated with gastroesophageal reflux disease relapse in primary care patients successfully treated with a proton pump inhibitor. / Factores de riesgo asociados a recaída de enfermedad por reflujo gastroesofágico en pacientes de primer nivel de atención exitosamente tratados con inhibidor de la bomba de protones.

BACKGROUND: There are no studies on the factors associated with gastroesophageal reflux disease (GERD) relapse in primary care patients. AIM: To identify the risk factors associated with GERD relapse in primary care patients that responded adequately to short-term treatment with a proton pump inhibitor. PATIENTS AND METHODS: A cohort study was conducted that included GERD incident cases. The patients received treatment with omeprazole for 4 weeks. The ReQuest questionnaire and a risk factor questionnaire were applied. The therapeutic success rate and relapse rate were determined at 4 and 12 weeks after treatment suspension. A logistic regression analysis of the possible risk factors for GERD relapse was carried out. RESULTS: Of the 83 patient total, 74 (89.16%) responded to treatment. Symptoms recurred in 36 patients (48.64%) at 4 weeks and in 13 patients (17.57%) at 12 weeks, with an overall relapse rate of 66.21%. The OR multivariate analysis (95% CI) showed the increases in the possibility of GERD relapse for the following factors at 12 weeks after treatment suspension: basic educational level or lower, 24.95 (1.92-323.79); overweight, 1.76 (0.22-13.64); obesity, 0.25 (0.01-3.46); smoking, 0.51 (0.06-3.88); and the consumption of 4-12 cups of coffee per month, 1.00 (0.12-7.84); citrus fruits, 14.76 (1.90-114.57); NSAIDs, 27.77 (1.12-686.11); chocolate, 0.86 (0.18-4.06); ASA 1.63 (0.12-21.63); carbonated beverages, 4.24 (0.32-55.05); spicy food 7-16 times/month, 1.39 (0.17-11.17); and spicy food ≥ 20 times/month, 4.06 (0.47-34.59). CONCLUSIONS: The relapse rate after short-term treatment with omeprazole was high. The consumption of citrus fruits and NSAIDs increased the possibility of GERD relapse.

A chain-of-states acceleration method for the efficient location of minimum energy paths.

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.

Dietary anhydrous milk fat naturally enriched with conjugated linoleic acid and vaccenic acid modify cardiovascular risk biomarkers in spontaneously hypertensive rats.

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.

First-principles simulations of lithium melting: stability of the bcc phase close to melting.

We report large-scale first-principles simulations of melting of four different phases of Li at pressures ranging from 0 to 50 GPa. We find excellent agreement with existing experimental data at low pressures, and confirm that above 10 GPa the melting line develops a negative slope, in parallel to what occurs for Na at 30 GPa. Surprisingly, our results indicate that the melting temperature of the bcc phase is always higher than that of fcc Li, suggesting the intriguing possibility of the existence of a narrow field of bcc stability separating the fcc and liquid phases, as predicted by Alexander and McTague [Phys. Rev. Lett. 41, 702 (1978)].

Amphiphillic organic crystals.

The amphiphillic character, that is, the capacity to simultaneously attract and repel water, has been traditionally reserved to organic molecules such as phospholipids and surfactants, containing both hydrophilic and hydrophobic groups within the same molecule. However, this general concept can be extended to artificial structures such as micrometer-sized particles, the so-called Janus particles, and patterned surfaces. Here we provide an example of an amphiphillic crystalline solid, l-alanine, by combining atomic force microscopy measurements performed on two different cleavage surfaces showing contrasting behaviors when exposed to water vapor, with computer simulations that allow us to clarify the dipolar origin of this behavior. Although we take l-alanine as an example, our results should apply quite generally to dipolar molecular crystals.

Path integral calculation of free energies: quantum effects on the melting temperature of neon.

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.

LH improves early follicular recruitment in women over 38 years old.

Although the capacity of recombinant FSH alone to induce folliculogenesis is undisputed, many believe that follicular recruitment in women over 38 years old could be improved by supplementing rFSH with human menopausal gonadotrophin (HMG). The present study sought to determine whether recombinant LH could reproduce the effect of HMG in women over 38 years during ovulation induction. Fifty-eight patients received rFSH (225 IU/day) supplemented with one ampoule of HMG (75 IU of FSH/75 IU of LH/HCG per day) for 5 days. Another 36 patients received rFSH (300 IU/day) supplemented with one ampoule of rLH (75 IU/day), also for 5 days. Both groups of patients received similar amounts of rFSH (1500 IU), LH/HCG (375 IU) and rLH (375 IU) and recruited a similar number of follicles as counted on day 6 (4.07 +/- 3.1 in the HMG group versus 3.7 +/- 3.2 in the LH group respectively) or on the day that human chorionic gonadotrophin (HCG) was indicated (6.5 +/- 2.7 versus 5.8 +/- 2.5 respectively). Ovarian stimulation was shorter, but not significantly so, in the group of patients receiving rFSH + HMG (10.5 +/- 1.7 days) than in the group of patients treated with rFSH +/- rLH (12 +/- 1.8 days). Significantly more MII oocytes were seen in the group treated with rFSH + rLH than in the group treated with rFSH + HMG (93.1 versus 75.3%, P < 0.05). With respect to pregnancy rates, 14/54 (26%) patients receiving rFSH + HMG and 16/34 (47%) patients receiving rFSH + rLH had a positive serum HCG. No significant difference in the number of miscarriages was observed between the two groups. In conclusion, the present results seem to indicate that rLH could be the HMG component that aids early follicular recruitment.

Phase diagram of silicon from atomistic simulations.

In this Letter we present a calculation of the temperature-pressure phase diagram of Si in a range of pressures covering from -5 to 20 GPa and temperatures up to the melting point. The phase boundaries and triple points between the diamond, liquid, beta-Sn, and Si34 clathrate phases are reported. We have employed efficient simulation techniques to calculate free energies and to numerically integrate the Clausius-Clapeyron equation, combined with a tight-binding model capable of an accuracy comparable to that of first-principles methods. The resulting phase diagram agrees well with the available experimental data.

Timing ovulation for intrauterine insemination with a GnRH antagonist.

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.

Influence of boron supplementation on vertebral and femoral bone mass in rats on strenuous treadmill exercise. A morphometric, densitometric, and histomorphometric study.

We studied the effect of boron supplement on experimental osteopenia caused by strenuous exercise in 93- d-old female Wistar rats. A control group of 15 rats was not manipulated. The exercise group of 30 rats was divided into 2 groups of 15 rats each, one that was fed a diet supplemented with 50 mg/kg of boron in the form of Na(2)B(4)O(7), and other that, did not receive a boron supplement. The length and weight were determined in the femur and fifth lumbar vertebra and the bone mineral content and density were assessed through densitometry, and trabecular bone volume, trabecular number, trabecular thickness, and trabecular separation with histomorphometry. The femur length and weight, and vertebra weight, and femur and vertebra bone mineral content and density were significantly lower and the trabecular separation was higher in the exercise group than in the others (p < 0.005 in all). The femur weight, bone mineral content and density, trabecular bone volume and trabecular thickness, were significantly higher in the exercise plus boron group (p < 0.005 to 0.0001). It was concluded that boron preserves bone mass in rats that have been exposed to intense exercise.

Effect of uterine horn ligation on bone mass: an experimental study in rats.

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.

Bone mass, bone metabolism, gonadal status and body mass index.

Weight and gonadal status are the main determinants of bone mass in women. Because of this it is important to study which influences it more. The effect of weight (expressed as body mass index, BMI) and gonadal status of women on total-body bone mineral content (TBBMC) and regional bone mineral content (BMC) was investigated. A total of 373 normal women (mean age 48.9 +/- 13.4 years) were studied: 171 postmenopausal women (mean age 59.3 +/- 9.5 years; years since menopause 11.3 +/- 6.7 years); 76 perimenopausal women (mean age 48.9 +/- 2.2 years); and 126 premenopausal women (mean age 34.7 +/- 7.4 years). In all the women, TBBMC and regional BMC were determined by dual-energy X-ray absorptiometry. Also biochemical markers of bone metabolism (total alkaline phosphatase and tartrate-resistant acid phosphatase) and serum estrone and estradiol were determined. When the women were stratified by gonadal status and BMI, thin women (BMI <20 kg/m2) had significantly lower TBBMC and regional BMC, lower gonadal steroid concentration and higher levels of biochemical markers than overweight (BMI 25-30 kg/m2) and obese (BMI >30 kg/m2) women, regardless of gonadal status. Overweight and obese women had findings suggestive of increased parathyroid activity, but greater bone mass. Weight rather than gonadal steroid concentration is the main determinant of bone mass in women regardless of gonadal status.

Can a determination of tartrate-resistant acid phosphatase predict postmenopausal loss of bone mass?

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.

Ultrasound bone mass in paraplegic patients.

STUDY DESIGN: A cross-sectional study. OBJECTIVE: To clarify the existing controversy with regard to whether paraplegic patients suffer a loss of bone mass in the upper limbs. SETTING: Madrid, Spain. METHODS: We evaluated bone mass by phalangeal ultrasonography in 35 male patients with paraplegia (mean age 49+/-12 years), and 25(OH)D3 and PTH to exclude the presence of osteomalacia and secondary hyperparathyroidism. Spasticity was evaluated according to the Ashworth scale. Patients were compared with a control group of 35 healthy male subjects (mean age 48+/-13 years). RESULTS: The patients had lower 25(OH)D3 levels and amplitude-dependent speed of sound (Ad-SOS) than controls (both P<0.001), and higher PTH levels (P<0.05). There was a statistically significant negative association between PTH and 25(OH)D3 levels (r=-0.52, P<0.0001, CI -0.73 to -0.22) and between 25(OH)D3 and injury duration (r=0.34, P<0.05, CI -0.60 to -0.01). There was no correlation between Ad-SOS values, levels of PTH or 25(OH)D3, and the injury duration. No significant difference in Ad-SOS values was found in patients grouped according to low-to-normal 25(OH)D3 level or according to normal-to-high PTH level. There were no differences in relation to muscle tone. Only alkaline phosphatase and tartrate-resistant acid phosphatase levels were higher in patients than in controls (both P<0.001). CONCLUSION: Paraplegic patients had a loss of phalangeal bone mass that was unrelated to the levels of vitamin D or PTH, or to muscle tone, so it seems to be related to increased bone resorption rather than to deficient bone formation.

Quantitative phalangeal bone ultrasound is normal after long-term gluten-free diet in young coeliac patients.

BACKGROUND AND AIMS: To determine bone mass using quantitative phalangeal bone ultrasound in young coeliac patients after a long-term gluten-free diet. SUBJECTS: A total of 99 patients with coeliac disease (CD) (52 girls, mean age 15.5 +/- 9.7 years; 47 boys, mean age 14.4 +/- 8.4 years) and 44 healthy subjects matched for age, weight and height (26 girls, mean age 18.4 +/- 9.9 years; 18 boys, mean age 16.3 +/- 11.2 years) were included in the study. METHODS: Bone status was assessed using an ultrasound device that measures amplitude-dependent speed of sound (Ad-SoS) in metres per second. Measurements were made on the phalanges (II-V) of the non-dominant hand, and an average value was computed. Nutrient intake was assessed using a 7-day record. RESULTS: Analysis of variance (ANOVA) and the unpaired t-test showed that the intake of phosphates (P < 0.05), proteins, fat and carbohydrates (P < 0.005 in all) was higher in patients than in controls. No significant difference in Ad-SoS was found between patients and controls (95% CI -10.9 to 60.6) in the overall group, in girls or boys, or in patients following a gluten-free diet strictly or partially. In the patients, only age (beta 4.01, 95% CI 1.84-6.16, P < 0.0005) and weight (beta 2.62, 95% CI 1.53-3.70, P < 0.0001) showed a significant positive relation with Ad-SoS. CONCLUSIONS: In patients with CD, gluten-free diet and increased nutritional intake were accompanied by normal bone mass values as determined by ultrasound on phalanges.

Behavior of phalangeal bone ultrasound in normal women with relation to gonadal status and body mass index.

The behavior of phalangeal bone ultrasound was studied, measured by amplitude-dependent speed of sound (Ad-SOS) in meters per second, in 324 normal women (mean age 48.9 +/- 13.7 years) classified by gonadal status (premenopausal, perimenopausal and postmenopausal) and body mass index (BMI, thin, normal, overweight and obese). Ad-SOS differed significantly with gonadal status and BMI (p<0.0001 for all). In the overall group of women, Ad-SOS correlated negatively with age (r=-0.84, p<0.0001), weight (r=-0.16, p<0.005), BMI (r=-0.27, p<0.0001), and tartrate-resistant acid phosphatase concentration (TRAP) (r=-0.35, p<0.0001). The negative correlation remained significant in the groups separated by gonadal status, but to a lesser extent. After adjusting for confounding variables such as age and weight, Ad-SOS was dependent on age (but not on weight or BMI) in the overall group of women and in the gonadal status groups. In conclusion, Ad-SOS values differed significantly with gonadal status and BMI, and correlated negatively with TRAP. The plot of Ad-SOS against age differed significantly with gonadal status as well as BMI.