bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical effect observation of intravenous application of zoledronic acid in patients with cervical spondylosis and osteoporosis after anterior cervical discectomy and fusion: A randomized controlled study
Authors: Liu Bin , Liu Xiangyang , Chen Yixin , Wang GuoPing , Wang Guohua , Shen Xiongjie , Liu Hongzhe , Liao Xiaoyun
Published: May 2019

Objective:

To observe the clinical effect of zoledronic acid (ZA) in patients with cervical spondylosis and osteoporosis after anterior cervical discectomy and fusion (ACDF) surgery.

Methods:

All selected patients were divided into the study group and the control group according to the sequence of surgery time. In the study group, 5 mg (100 ml) of ZA was applied intravenously as intervention on the 5 day after ACDF surgery. Patients were followed up regularly after surgery.

Results:

Forty-three cases completed the follow-ups (21/22), the neck disability index (NDI) score significantly decreased at the 3rd month after surgery in both groups, it came to a plateau at the 6th month after surgery, and it had some rise at the 12th month after surgery, but the NDI score was lower in the study group at the 12th month after surgery ( p < 0.05). C-telopeptide of type I collagen (CTX) and amino terminal propeptide of type I procollagen of bone turnover markers in the study group showed a downward trend after surgery, among which CTX decreased significantly and no significant changes in the control group. At the 12th month after surgery, the bone mineral density of lumbar spine area in the study group was significantly improved ( p < 0.05). During the 3rd and the 6th month follow-up after surgery, 1/2 osteogenesis rate of the study group was significantly higher ( p < 0.05). However, all patients in the two groups obtained stable fusion at the 12th month follow-up after surgery.

Conclusions:

For patients with cervical spondylosis and osteoporosis, intravenous application of ZA after ACDF surgery can shorten the time of cervical osteogenesis, promote local bone graft fusion, and improve the postoperative clinical effect to some extent.
No Effect of Musical Training on Frequency Selectivity Estimated Using Three Methods
Authors: Moore Brian C. J. , Wan Jie , Varathanathan Ajanth , Naddell Sophie , Baer Thomas
Published: May 2019

It is widely believed that the frequency selectivity of the auditory system is largely determined by processes occurring in the cochlea. If so, musical training would not be expected to influence frequency selectivity. Consistent with this, auditory filter shapes for low center frequencies do not differ for musicians and nonmusicians. However, it has been reported that psychophysical tuning curves (PTCs) at 4000 Hz were sharper for musicians than for nonmusicians. This study explored the origin of the discrepancy across studies. Frequency selectivity was estimated for musicians and nonmusicians using three methods: fast PTCs with a masker that swept in frequency, “traditional” PTCs obtained using several fixed masker center frequencies, and the notched-noise method. The signal frequency was 4000 Hz. The data were fitted assuming that each side of the auditory filter had the shape of a rounded-exponential function. The sharpness of the auditory filters, estimated as the Q10 values, did not differ significantly between musicians and nonmusicians for any of the methods, but detection efficiency tended to be higher for the musicians. This is consistent with the idea that musicianship influences auditory proficiency but does not influence the peripheral processes that determine the frequency selectivity of the auditory system.
Evacuation Shelter Deficits for Socially Vulnerable Texas Residents During Hurricane Harvey
Authors: Karaye Ibraheem M. , Thompson Courtney , Horney Jennifer A.
Published: May 2019

Background:

Socially vulnerable residents of US Gulf Coast counties have higher exposure to physical hazards and disaster-associated risks. Evacuation is one way to mitigate the consequences of disaster exposure among socially vulnerable populations. However, it is unknown whether existing evacuation shelter capacity and locations in designated hurricane evacuation zones of Texas are adequate to accommodate persons with housing and transportation needs. This study estimated the evacuation shelter deficit arising from demand from socially vulnerable residents of the Houston-Galveston area.

Methods:

Spatial statistical methods including Global Moran’s I and Getis-Ord (Gi*) were used to measure spatial autocorrelation and identify census tracts in the study area with high (hot spots) and low (cold spots) social vulnerability in both housing and transportation domains. The shelter deficit in each county within the study area was estimated as well as for the entire Houston-Galveston Metropolitan Statistical Area.

Results:

Designated evacuation zones in the Houston-Galveston area have an overall shelter deficit of 163 317 persons. Shelters in the area can only accommodate 36% of evacuees with significant housing and transportation needs, while 3 of 4 counties had county-specific evacuation shelter deficits. The highest deficits were in Harris County, where Houston is located, and the lowest were in Matagorda County, a rural county southwest of Harris County.

Conclusion:

Emergency managers and other authorities should consider data related to demand from socially vulnerable residents for public shelters during disasters and increase shelter capacity in certain locations to address evacuation shelter shortage for vulnerable persons in designated evacuation zones of Texas.
Access to Physical Therapy for Pediatric and Adolescent Patients Following Orthopedic Surgery
Authors: Sarkisova Natalya , Smith Ryan , VandenBerg Curtis , Pace J. Lee , Goldstein Rachel Y.
Published: May 2019

The objective of this study was to evaluate the relationship between insurance status and access to physical therapy (PT). Masked telephone interviews with PT facilities in a major metropolitan area were conducted with researchers posing as parents of children. Each facility was called twice: once with a private insurer and once with a government insurer. Earliest available appointment, if the facility accepted insurance, and amount of time required to return a call were recorded. Fifty-four PT clinics responded. Clinics that accepted private insurance were significantly greater than the proportion that accepted government insurance (85.2% vs 14.8%, P < .001). There was no significant difference in time between initial call and first offered appointment, in the 2 insurance conditions (private: 8.09 days, government: 8.67 days, P = .33). There were no significant differences in appointment delays between both insurance conditions. Our study found there was a significantly lower rate of children with government-funded insurance that had access to postsurgical rehabilitation.
The behaviour of as-applied and artificially weathered silica–epoxy consolidants on a typical Mediterranean porous limestone: a comparison with TEOS
Authors: Briffa Sophie M. , Vella Daniel A.
Published: May 2019

A water based epoxy–silica consolidant and variants of the same consolidant containing silica nanoparticles (NP) were applied to Globigerina Limestone (GL) blocks by brushing and full immersion techniques. The consolidants were applied for their improved strength, toughness and adhesion to the stone surface. As-consolidated dried stone blocks were characterised (colour, total porosity, pore size distribution and microstructure) and their physical and mechanical properties assessed by a water uptake by capillary test, drilling resistance and resistance to salt crystallisation test. In another set of experiments, the consolidated limestone blocks were subject to 28 wet–dry cycles (8-h wet, 16-h dry) in a weathering chamber. The physical and mechanical properties of the weathered consolidated limestone blocks were then re-assessed. Parallel tests were also performed on tetraethyl orthosilicate (TEOS)-consolidated and untreated GL blocks. The water absorption coefficients of limestone blocks consolidated by brush-applied epoxy–silica dropped marginally. No significant changes to the water absorption coefficients were recorded after weathering. The drilling resistance curves showed a clear improvement of the mechanical properties of epoxy–silica treated GL, but the effects of the consolidants were reversed with weathering. The epoxy–silica consolidants reduced the resistance of GL to salt crystallisation. This resistance was partly restored after weathering, corroborating the drilling resistance results, and supporting the consolidation reversal hypothesis. Test results for the epoxy–silica consolidants applied by immersion showed similar trends, albeit complicated by pore blocking. The formation of an undesirable surface crust with epoxy–silica consolidants remains a pertinent issue with such hybrid materials. The behaviour of TEOS-consolidated GL was very different to the epoxy–silica consolidants and this can be traced to the hydrophobic nature of TEOS that persisted months after application.
Clinical Guidelines and PTH Measurement: Does Assay Generation Matter?
Authors: Smit Marjon A , van Kinschot Caroline M J , van der Linden Joke , van Noord Charlotte , Kos Snježana
Published: May 2019

PTH is an important regulator of calcium and phosphate homeostasis and bone remodeling. It is metabolized into PTH fragments, which are measured to a different extent by PTH assays of different generations because of differences in fragments recognized and lack of assay standardization. PTH is measured in the workup of several conditions, and clinical guidelines provide recommendations concerning these measurements. This review provides an overview of the impact of differences between PTH assays, applying distinct clinical guidelines for primary and secondary hyperparathyroidism and perioperative use of PTH measurements. Guidelines deal with PTH measurement in different ways, recommending either trend monitoring, the use of a fold increase of the upper reference limit, or an absolute PTH cutoff value. For classic primary hyperparathyroidism (PHPT), the type of PTH assay used will not affect diagnosis or management because the precise concentration of PTH is less relevant. In chronic kidney disease, the guideline recommends treating secondary hyperparathyroidism above a twofold to ninefold PTH increase, which will result in different clinical decisions depending on the assay used. For patients after bariatric surgery, guidelines state absolute cutoff values for PTH, but the impact of different generation assays is unknown because direct comparison of PTH assays has never been performed. During parathyroid surgery, PTH measurements with a third-generation assay reflect treatment success more rapidly than second-generation assays. Increased awareness among clinicians regarding the complexity of PTH measurements is warranted because it can affect clinical decisions.
Panorama similarity and navigational knowledge in the nocturnal bull ant, Myrmicia midas
Authors: Freas Cody A. , Cheng Ken
Published: May 2019

Nocturnal ants forage and navigate during periods of reduced light, making detection of visual cues difficult, yet they are skilled visual navigators. These foragers retain visual panoramic memories both around the nest and along known routes for later use, be it to return to previously visited food sites or to the nest. Here, we explore the navigational knowledge of the nocturnal bull ant, Myrmecia midas, by investigating differences in nest-ward homing after displacement of three forager groups based on similarities in the panoramas between the release site and previously visited locations. Foragers that travel straight up the foraging tree or to close trees around the nest show reduced navigational success in orienting and returning from displacements compared to individuals that forage further from the nest site. By analysing the cues present in the panorama, we show that multiple metrics of forager navigational performance correspond with the degree of similarity between the release site panorama and panoramas of previously visited sites. In highly cluttered environments, where panoramas change rapidly over short distances, the views acquired near the nest are only useful over a small area and memories acquired along foraging routes become critical.
Distinctive mechanisms underlie the emission of social electric signals of submission in Gymnotus omarorum
Authors: Comas Virginia , Langevin Kim , Silva Ana , Borde Michel
Published: May 2019

South American weakly electric fish (order Gymnotiformes) rely on a highly conserved and relatively fixed electromotor circuit to produce species-specific electric organ discharges (EOD) and a variety of meaningful adaptive EOD modulations. The command for each EOD arises from a medullary pacemaker nucleus composed by electrotonically coupled intrinsic pacemaker and bulbospinal projecting relay cells. During agonistic encounters Gymnotus omarorum signals submission by interrupting its EOD (offs) and by emitting transient high rate barrages of low amplitude discharges (chirps). Previous studies in gymnotiformes have shown that electric signal diversity is based on the segregation of descending synaptic inputs to pacemaker or relay cells and differential activation of the neurotransmitter receptors -for glutamate or γ-aminobutyric acid (GABA)- of these cells. Therefore, we tested whether GABAergic and glutamatergic inputs to pacemaker nucleus neurons are involved in the emission of submissive electric signals in G. omarorum. We found that GABA applied to pacemaker cells evokes EOD interruptions that closely resembled natural offs. Although in other species chirping is likely due to glutamatergic suprathreshold depolarization of relay cells, here, application of glutamate to these cells was unable to replicate the emission of this submissive signal. Nevertheless, chirp-like discharges were emitted after the enhancement of excitability of relay cells by blocking an IA-type potassium current and, in some cases, by application of vasotocin, a status-dependent modulator peptide of G. omarorum agonistic behavior. Modulation of electrophysiological properties of pacemaker nucleus neurons in gymnotiformes emerges as a novel putative mechanism, endowing electromotor networks with higher functional versatility.
Eccentric resistance training and β-Hydroxy-β-methylbutyrate free acid affects muscle PGC-1α expression and serum irisin, nesfatin-1 and resistin
Authors: Shirvani Hossein , Rahmati-Ahmadabad Saleh , Broom David Robert , Mirnejad Reza
Published: May 2019

The hypothalamus controls metabolism and feeding behavior via several signals with other tissues. Exercise and supplements can change hypothalamic signaling pathways, so the present study investigated the influence of eccentric resistance training and β-Hydroxy-β-methylbutyrate free acid supplement on PGC-1α expression, serum irisin, nesfatin-1 and resistin concentrations. Thirty-two male rats (8 weeks old, 200±17 g body mass) were randomized to control (CON), β-Hydroxy-β-methylbutyrate free acid (HMB) supplementation, eccentric resistance training (ERT), and β-Hydroxy-β-methylbutyrate free acid supplementation plus eccentric resistance training (HMB+ERT) groups. Training groups undertook eccentric resistance training (6 weeks, 3 times a week) and supplement groups consumed HMB-FA orally (76 mg/kg/day). Twenty-four hours after the last training session, rats were sacrificed after which serum and triceps brachii muscle were collected and sent to the laboratory for analyses. Two-way ANOVA and Pearson correlation were employed (significant level: P< 0.05). The results showed that eccentric resistance training increases skeletal muscle PGC-1α gene expression, as well as serum levels of irisin and nesfatin-1 (P= 0.001). Eccentric resistance training decreases serum concentration of resistin (P= 0.001). HMB-FA supplement increases skeletal muscle PGC-1α gene expression (P= 0.002), as well as serum concentartion of irisin and nesfatin-1 (P= 0.001). HMB-FA decreases the serum concentration of resistin (P= 0.001). Significant correlations were observed between PGC-1α gene expression and serum concentrations of irisin, nesfatin-1 and resistin. Generally, HMB-FA with eccentric resistance training may induce crosstalk between releasing peptides from other tissues and increases maximal strength. Their combination had a more substantial effect than each intervention in isolation.
Sideline Coverage of Figure Skating Events
Authors: Lambrinakos-Raymond Kristen , FitzGerald Brian , Geminiani Ellen T.
Published: May 2019

The sport of figure skating has evolved to include various disciplines and athletes continue to push the limits of the skills they perform, thus increasing the potential for injury in practice, as well as in competition. To provide optimal rink side coverage, health care professionals must be aware of the elements skaters perform and the injuries to be expected. Appropriate planning and coordination of medical services is required to ensure adequate and timely care of injured figure skaters. Protocols developed for local, national, and international events are available to assist in this process.
Protein Supplementation Does Not Augment Adaptations to Endurance Exercise Training
Authors: JONVIK KRISTIN L. , PAULUSSEN KEVIN J. M. , DANEN SHIANNAH L. , CEELEN INGRID J. M. , HORSTMAN ASTRID M. , WARDENAAR FLORIS C. , VAN LOON LUC J. C. , VAN DIJK JAN-WILLEM
Published: May 2019

Introduction

Recently, it has been speculated that protein supplementation may further augment the adaptations to chronic endurance exercise training. We assessed the effect of protein supplementation during chronic endurance exercise training on whole-body oxidative capacity (V˙O2max) and endurance exercise performance.

Methods

In this double-blind, randomized, parallel placebo-controlled trial, 60 recreationally active males (age, 27 ± 6 yr; body mass index, 23.8 ± 2.6 kg·m−2; V˙O2max, 47 ± 6 mL·min−1·kg−1) were subjected to 12 wk of triweekly endurance exercise training. After each session and each night before sleep, participants ingested either a protein supplement (PRO; 28.7 g casein protein) or an isoenergetic carbohydrate placebo (PLA). Before and after the 12 wk of training, V˙O2max and endurance exercise performance (~10-km time trial) were assessed on a cycle ergometer. Muscular endurance (total workload achieved during 30 reciprocal isokinetic contractions) was assessed by isokinetic dynamometry and body composition by dual-energy x-ray absorptiometry. Mixed-model ANOVA was applied to assess whether training adaptations differed between groups.

Results

Endurance exercise training induced an 11% ± 6% increase in V˙O2max (time effect, P < 0.0001), with no differences between groups (PRO, 48 ± 6 to 53 ± 7 mL·min−1·kg−1; PLA, 46 ± 5 to 51 ± 6 mL·min−1·kg−1; time–treatment interaction, P = 0.50). Time to complete the time trial was reduced by 14% ± 7% (time effect, P < 0.0001), with no differences between groups (time–treatment interaction, P = 0.15). Muscular endurance increased by 6% ± 7% (time effect, P < 0.0001), with no differences between groups (time–treatment interaction, P = 0.84). Leg lean mass showed an increase after training (P < 0.0001), which tended to be greater in PRO compared with PLA (0.5 ± 0.7 vs 0.2 ± 0.6 kg, respectively; time–treatment interaction, P = 0.073).

Conclusion

Protein supplementation after exercise and before sleep does not further augment the gains in whole-body oxidative capacity and endurance exercise performance after chronic endurance exercise training in recreationally active, healthy young males.
Aggregation and the Gravity Equation
Authors: Redding Stephen J. , Weinstein David E.
Published: May 2019

One of the most successful empirical relationships in international trade is the gravity equation. A key decision for researchers in estimating this relationship is the level of aggregation, since the gravity equation is log linear, whereas aggregation involves summing the level rather than the log of trade. In this paper, we derive a Jensen's inequality correction term for nested constant elasticity of substitution preferences, such that a log-linear gravity equation holds exactly for each nest. We provide evidence that sectoral composition is quantitatively relevant for the aggregate effect of distance on international trade, particularly for more disaggregated definitions of sectors.
Mobile Wallet and Entrepreneurial Growth
Authors: Agarwal Sumit , Qian Wenlan , Yeung Bernard Y. , Zou Xin
Published: May 2019

Using mobile wallet and card transaction data from a leading Singapore bank, this paper studies the effect of a mobile wallet payment technology introduction in 2017 on business growth. We find that mobile wallet usage doubled after the new technology introduction, and the improved payment efficiency generated a significant spillover effect. Small merchants experienced a monthly increase in debit and credit card sales amount (count) of 3.5 percent (3.4 percent) compared to large merchants. The payment technology promoted sales growth primarily for new businesses by facilitating customer acquisition.
A Reason to Wait: The Effect of Legal Status on Teen Pregnancy
Authors: Kuka Elira , Shenhav Na’ama , Shih Kevin
Published: May 2019

Although teen pregnancy has been on the decline in the United States, it remains among the highest within developed countries. Hispanics, who are more likely to be undocumented immigrants, lead this trend, yet the role of legal status has yet to be considered. To investigate this question, we examine teenage fertility responses to the Deferred Action for Childhood Arrivals (DACA) program, which provides temporary legal status to undocumented youth. We find that DACA reduced the likelihood of having a teenage birth by 1.6 percentage points and eliminated roughly half of the gap in teenage childbearing between documented and undocumented women.
Who Pays for Rent Control? Heterogeneous Landlord Response to San Francisco’s Rent Control Expansion
Authors: Diamond Rebecca , McQuade Tim , Qian Franklin
Published: May 2019

Using a 1994 law change, we exploit quasi-experimental variation in the assignment of rent control in San Francisco to study which types of landlords bear the burden of decreased rental payments versus substitute away from supplying rent-controlled housing. We find rent control leads to a long-run decrease in the supply of rental housing. This effect is more pronounced among properties managed by corporate landlords versus individual landlords. Raising revenue for rental subsidies through rent control appears to be regressive, since corporations can evade the tax burden of rent control more easily, likely due to their superior access to capital.
Housing Supply Dynamics under Rent Control: What Can Evictions Tell Us?
Authors: Asquith Brian J.
Published: May 2019

Measuring how rent-controlled landlords change their housing supply in response to rent increases is difficult, because new construction is automatically exempt. This paper explores evictions as a barometer for landlords' willingness to return their units to market when prices increase using San Francisco data. I find no evidence that controlled landlords turnover existing tenants to return their units to market, and some evidence they instead withdraw individual units. I also look at other ways of exiting controls, and find that small landlords are 54 percent more likely to first apply to condo-convert when condo prices rise 5.4 percent.
Matching with Stochastic Arrival
Authors: Thakral Neil
Published: May 2019

This paper examines efficiency and fairness properties in a dynamic allocation problem. The model applies to situations in which objects of different types arrive stochastically over time and must be assigned to agents in a queue, such as the allocation of public housing units. The main result demonstrates the impossibility of designing an allocation mechanism in an environment with stochastic arrival that can guarantee resulting assignments that are efficient or fair ex post.
Unequal Distributions: EG DNA versus DINA Approach
Authors: Zwijnenburg Jorrit
Published: May 2019

In the past years, projects have been initiated to develop distributional results in line with national accounts totals. Their results differ from those obtained from micro statistics, but also show differences across projects, due to different underlying concepts and methodology to derive the results. This paper explains the differences between the work by the OECD-Eurostat Expert Group on Disparities in National Accounts (EG DNA) and the work on Distributional National Accounts (DINA) as developed in the context of the World Wealth and Income Database. It shows that different concepts and assumptions in the compilation process may significantly affect distributional results.
How Elastic is the Demand for Tax Havens? Evidence from the US Possessions Corporations Tax Credit†
Authors: Garrett Daniel , Suárez Serrato Juan Carlos
Published: May 2019

Why do some firms adopt certain tax havens, and how sensitive is the demand for tax havens? We address these questions by studying how the repeal of section 936 tax credits affected firms with affiliates in Puerto Rico. We first describe the characteristics of US multinationals that were exposed to section 936. We then show that the market value of exposed firms decreased after losing access to section 936, implying that firms could not perfectly substitute to other tax havens. Finally, we find that firms exposed to section 936 did not respond by expanding their network of tax havens.
Flow Origins of Labor Force Participation Fluctuations
Authors: Elsby Michael , Hobijn Bart , Karahan Fatih , Kos¸ar Gizem , S¸ahin Ays¸egül
Published: May 2019

We investigate the origins of cyclical and trend movements in the labor force participation rate (LFPR) using a three-state flow decomposition. The procyclicality of LFPR can be traced to cyclical flows between employment and unemployment. By contrast, labor force entry and exit explain virtually all of the trend movements. Among men, rising labor force exit rates account for two-thirds of the trend decline in male LFPR since the 1990s. For women, trend increases in female LFPR during the 1990s were dominated by declining exit rates, while the trend decline since the Great Recession can be traced to declining entry rates.
China versus the United States: IMS Meets IPS
Authors: Farhi Emmanuel , Maggiori Matteo
Published: May 2019

Currently both the International Monetary System (IMS) and the International Price Systems (IPS) are dominated by the United States. The emergence of China, both as reserve currency and as a currency of invoicing, is likely to disrupt this status quo. We provide a framework to understand the forces that will shape this transition and identify sources of instability. We highlight the risk of an abrupt shift triggered by a run on the dollar.
Augmenting Pre-Analysis Plans with Machine Learning
Authors: Ludwig Jens , Mullainathan Sendhil , Spiess Jann
Published: May 2019

Concerns about the dissemination of spurious results have led to calls for pre-analysis plans (PAPs) to avoid ex-post “p-hacking.” But often the conceptual hypotheses being tested do not imply the level of specificity required for a PAP. In this paper we suggest a framework for PAPs that capitalize on the availability of causal machine-learning (ML) techniques, in which researchers combine specific aspects of the analysis with ML for the flexible estimation of unspecific remainders. A “cheap-lunch” result shows that the inclusion of ML produces limited worst-case costs in power, while offering a substantial upside from systematic specification searches.
Neutral Bargaining in Financial Over-The-Counter Markets
Authors: Kim Jin Yeub
Published: May 2019

I study bargaining over prices between two investors in financial over-the-counter markets with asymmetric information. I focus on environments in which an asset owner has private information about both her liquidity state and asset quality, and so a buyer is uncertain about the owner's true motive for selling--whether it is because of a liquidity need or because of a low asset valuation. I apply the concept of neutral bargaining solution to characterize the prices at which the investors trade with each other. I illustrate the implications for asset prices in over-the-counter markets where private information may be prevalent.
Toward the Next Generation of Scholarship: Challenges and Opportunities for Full Participation in PhD Training in Economics
Authors: Jeitschko Thomas D.
Published: May 2019

A great advantage of our rigorous doctoral training is that as PhD economists we speak a common language that allows for efficient vetting and quick dissemination of ideas and insights. But what good is sophisticated grammar and a powerful vocabulary if the contents of our narratives are lacking? Our top three criteria for admissions to PhD programs are prior coursework in math, the quantitative GRE score, and prior coursework in economics. To attract top talent and prevent becoming a stagnant discipline that loses the influence we have in society and academia, students' creativity, originality, and drive should receive more weight.
The Gender Gap in Undergraduate Economics Course Persistence and Degree Selection
Authors: Ahlstrom Laura J. , Asarta Carlos J.
Published: May 2019

This study examines male and female course persistence and choice of economics degree via a combination of student, instructor, and structural characteristics. We find that students of both genders who declare economics as their major are more likely to take additional economics courses than their non-major peers. Additionally, students' economics grades are a significant determinant of course persistence and degree selection, but men and women respond somewhat differently to their absolute and relative grades. Finally, men's economics degree selection is significantly correlated with their math abilities, while women's economics degree selection is correlated with both their math and verbal aptitudes.
A Comparative Study of Seminal Plasma and Blood Serum Macro and Trace Elements in the the Breeding (October) and the Non-Breeding (April) Seasons in Merino Ram
Authors: BULBUL B. , AKALIN P. P. , BAŞPINAR N. , BUCAK M. N. , KIRBAŞ M. , ÖZTÜRK C. , GÜNGÖR S. , AKBULUT K.
Published: May 2019

In this study, it was aimed to investigate the concentrations of macro and trace elements in seminal plasma and blood serum in the breeding (October) and the non-breeding (April) seasons in Merino Ram. Nineteen Merino Rams, aged 18-24 months, were involved in the study. Blood (once) and ejaculate samples (6 replicates) were taken in the breeding (October) and the non-breeding (April) seasons. Blood serum, seminal plasma and diet Calcium, Sodium, Potassium, Magnesium, Phosphorus, Sulfur, Zinc, Selenium, Chrome, Manganese, Nickel, Molybdenum and Boron concentrations were determined by ICP-AES. In blood serum, Sodium and Selenium concentrations were higher (p<0.05 and 0.001, respectively) in the the breeding season than in non-breeding season, whereas Potassium, Chromium and Boron concentrations were lower (p<0.05, 0.001 and 0.001, respectively) in the breeding season than in the non-breeding season. In seminal plasma Calcium, Sodium, Zinc and Manganese concentrations were higher (p<0.05, 0.001, 0.01 and 0.05, respectively) in the breeding season than in the non-breeding season, whereas Phosphorus, Chrome, Molybdenum and Boron concentrations were lower (p<0.001, 0.001, 0.05 and 0.001, respectively) in the breeding season than in the non-breeding season. No difference was detected regarding the other elements. The higher levels of Cr and B in the non-breeding season compared to the breeding season both in serum and seminal plasma, regardless of diet intake, suggest that these elements may play a crutial role on male fertility in Merino Ram.
Feeding a definite concentration of eicosapentaenoic and docosahexaenoic fatty acids to laying hens
Authors: NASSEF E. E. , BAKR A. A. , SALAMA A. S.
Published: May 2019

The experiment designed to study the influences of nutritional eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids (FA) on performance, egg yolk fat characteristics and FA profile in laying hens. From 30 to 36 weeks of age, 180 laying hens were allotted randomly to 2 dietary treatments, each of 6 replicates (15 birds for each replicate). The control diet was supplied with soy oil while the experimental diet was supplied with EPA and DHA to create 2 different ratio of n-6 to n-3 FA (18.8:1 and 5:1, respectively). The egg production % was recorded daily. The eggs were weighed to estimate egg mass. Also, feed consumption was recorded daily and the feed conversion ratio (FCR) was estimated. The FA profile of egg yolk was determined in the last week of the experiment. The dietary EPA and DHA resulted in significantly higher egg production (76.89 versus 67.23%), weightier egg mass (42.46 versus 37. 72 g) and lower FCR (2.49 versus 2.72) than the control. Also, supplying the dietary EPA and DHA was reflected in increasing of total polyunsaturated and n-3 FA in the eggs. Moreover, reducing the ratio of n-6 to n-3 FA to 5:1 decreased egg triglycerides, total cholesterol and cholesterol associated with low density lipoprotein and very low density lipoprotein. In conclusion, supplying EPA and DHA in the diet of laying hens positively influences performance, egg yolk FA profile and cholesterol. Practically, EPA and DHA could be used in laying hen diets to improve their performance and enhance public health of egg consumers.
The investigation of xylazine, detomidine, isoflurane and sevoflurane anaesthetic combinations on clinical, laboratory and cardiovascular parameters and on intraocular pressure in horses
Authors: EROL H. , ARICAN M.
Published: May 2019

The aim of this study was to investigate the effects of anaesthetic combinations of xylazine, detomidine, sevoflurane and isoflurane on clinical, laboratory, and cardiovascular parameters as well as their effects on intraocular pressure in horses. Twenty-four mixed-breed horses (twelve male and twelve female) were used for this study. The horses were allocated into four groups (six horses in each group): XS (xylazine-sevoflurane), XI (xylazine-isoflurane), DS (detomidine-sevoflurane) and DI (detomidine-isoflurane). Clinical evaluations, hematological, biochemical tests and measurement of intraocular pressure were done before (0th), during (5th, 15th and 30th min) and at the end of anaesthesia (60th min). The detected differences were statistically evaluated. In conclusion, this study shows that the anaesthetic combinations of sevoflurane and isoflurane with xylazine and detomidine provided safe and suitable anaesthesia in horses. Our study did not reveal any statistical differences in intraocular pressure measurements. However, it should be noted that intraocular pressures were measured with the animals lying down and our results do not rule out changes in intraocular pressures in a standing position. We concluded that these anaesthesia protocols are suitable for ophthalmic surgery.
Ciliary body cysts associated with glaucoma in a Great Dane
Authors: PAPAVASILEIOU E. , DURIEUX P.
Published: May 2019

An 8-year-old female Great Dane, was referred to the Ophthalmology Unit of the Centre Hospitalier Vétérinaire (CHV) des Cordeliers, for corneal opacity of the left eye that did not respond to topical treatment, administered by the referring vet. On initial examination, bilateral ciliary body cysts were noticed. Lens subluxation, pseudo-plateau iris and glaucoma were observed on the left eye. The diagnosis was confirmed by applanation tonometry and high resolution ocular ultrasonography. Medical treatment resulted in temporary clinical improvement of the left eye. No signs of glaucoma were observed on the right eye upon the last re-check examination.
Controllability of joint integrity and mechanical properties of friction stir welded 6061-T6 aluminum and AZ31B magnesium alloys based on stationary shoulder
Authors: Wu Baosheng , Liu Jinglin , Song Qi , Lv Zan , Bai Wei
Published: May 2019

In order to improve joint integrity and reduce the amount of intermetallic compounds (IMCs), 6061-T6 Al and AZ31B Mg alloys were successfully joined by stationary shoulder friction stir welding (SSFSW). The stationary shoulder effectively enhanced the joint surface integrity and reduced the thickness reduction of the Al/Mg joint. The elimination of pin adhesion was beneficial to increasing material transfer and then improving interfacial joining length of Al/Mg joint. Extremely thin IMCs layer could be achieved because of the heat sink induced by the stationary shoulder. The maximum tensile strength of the Al/ Mg joint reached 137 MPa at a welding speed of 60 mm/min, rotating velocity of 1000 rpm and offset to Mg sheet of 0.3 mm, which was 130% higher than that of conventional joint. SSFSW is feasible and has the potential to join dissimilar materials with the formation of IMCs, such as Al/Mg alloys, Al/copper alloys, Al/titanium alloys and so on.
Dough moulding compound reinforced silicone rubber insulating composites using polymerized styrene butadiene rubber as a compatibilizer
Authors: Wu Weili , Huang He , Chen Zhe
Published: May 2019

Dough moulding compound (DMC) reinforced polymerized styrene butadiene rubber (SBR) / methyl vinyl silicone rubber (MVQ) composites were prepared, in which MVQ was matrix, DMC was a reinforcement phase and SBR was a compatibilizer. Dynamic thermomechanical analysis (DMA), infrared spectrum analysis (IR) and the effect of SBR and DMC content on mechanical properties, electrical insulating property and compatibility of the composites were investigated. The results showd that the morphology and thermal properties of the composites were improved when dough moulding compound was used as a reinforcement, and styrene butadiene rubber was compatibilizer, and had excellent insulating property with volume resistivity above 4.8×1012 Ω·m.
Comparación de métodos gravimétricos y termogravimétricos para la de obtención del porcentaje de residuo de asfalto de una emulsión asfáltica
Authors: Rodriguez Castro Ellen , Salazar Delgado Jorge , Zúñiga Araya Cindy
Published: May 2019

La caracterización de las emulsiones asfálticas incluye el ensayo de destilación para cuantificar el contenido de asfalto. Este ensayo se realiza desde hace mucho tiempo, tanto en Costa Rica como en otros países. Es un método tradicional y preciso, que ha representado una muy buena opción para la recuperación del asfalto residual de una emulsión asfáltica, pero consume mucho tiempo y  requiere de la pericia del analista para identificar  momentos clave de la separación.

En vista de que se pueden utilizar las nuevas tecnologías para la cuantificación de la composición de las emulsiones asfálticas, se propone aplicar técnicas de análisis termogravimétricos instrumentales.

La primera fase del proyecto consiste en determinar los parámetros que se deben utilizar en un analizador termogravimétrico (TGA, por sus siglas en inglés) para obtener resultados comparables con el método de destilación. Para lo cual se varían las rampas de temperatura y la velocidad de calentamiento en cada una de las muestras analizadas.

A pesar de que los resultados no presentan diferencias estadísticamente significativas, se percibe el efecto que tienen los cambios de parámetros en el análisis termogravimétricos en los resultados.

Los resultados obtenidos muestran que es posible utilizar los análisis termogravimétricos instrumentales para determinar el porcentaje de residuo asfáltico en la emulsión, pero además permite establecer las condiciones que deben definirse como parte de un procedimiento de análisis, según los resultados debe seleccionarse tasas de calentamiento de 10 °C/min o menores a 5° C/min. Asimismo se determina que las tasas de calentamiento moduladas no arrojan buenos resultados.

En la siguiente fase se compararán los métodos mencionados utilizando emulsiones fabricadas en el laboratorio, considerando los parámetros definidos en esta fase.
Determinación de la resistencia a la tracción del asfalto (BBS) y trabajo de adhesión (WaL,S) de los ligantes asfalticos, mediante determinaciones de ángulo de contacto.
Authors: Salazar Delgado Jorge Alberto , Pacheco Fallas Juan Francisco , Jimenez Alvarado Marìa Jose
Published: May 2019

Debido a los problemas generados por el agua en muchos de los pavimentos alrededor del mundo se ha buscado una forma de mejorar los materiales que componen las mezclas asfálticas. Con este fin se han desarrollado diferentes métodos para poder medir las propiedades de los materiales que se relacionen con el daño por humedad. Los métodos que se describen son conocidos como ensayos de goniometría y ensayos de resistencia a la tracción de asfaltos (ABS).

Parte de las investigaciones en este campo están enfocadas en las propiedades físico-químicas de los asfaltos relacionadas con falla por adhesión. Este artículo pretende describir dos de los principales métodos de ensayo utilizados en laboratorios para medir el trabajo de adhesión en los ligantes asfálticos y emulsiones. Los procedimientos aquí descritos pueden ser de interés para los ingenieros y profesionales que trabajan en el diseño de pavimentos y en áreas afines.
Concepto para un túnel de viento de vórtice variable
Authors: Monge Gapper Juan Gabriel
Published: May 2019

Se propone un diseño de bajo costo de un túnel de viento con vórtice variable, que mediante la inyección controlada de flujos cruzados direccionales, permite variar el tamaño y velocidad de rotación de los vórtices independientemente de la velocidad promedio del flujo. Se evita con ello la reconfiguración de la sección de estabilización, comúnmente utilizado en los túneles de capa limite. El uso de este túnel de viento en la escala y velocidad indicada serían para pruebas prácticas usando modelos a escala para cuantificar la interacción del viento atmosférico con construcciones civiles, caracterizar patrones de erosión de terrenos y transporte de sedimentos, y determinar los patrones generales de dispersión de contaminantes atmosféricos en ciertas escalas de terreno; podría utilizarse también para definir parámetros de calibración en modelos numéricos de flujo de fluidos a baja velocidad en dos dimensiones.
Proceso de normalización de métodos de ensayo de laboratorio para mezclas asfálticas en caliente (MAC)
Authors: Jiménez Acuña Mónica , Montero Vega Mariana
Published: May 2019

El Instituto de Normas Técnicas de Costa Rica (INTECO) nace en 1987 como respuesta a una necesidad costarricense de normalización técnica. INTECO ha evolucionado enormemente a través de los años elaborando una gama muy extensa de normativas con alrededor de 30 comités técnicos y más de 500 normas publicadas. Dentro de estos comités se encuentra la “CTN 04 Mezclas Bituminosas y Ligantes Asfalticos” perteneciente a la categoría de Mezclas Asfálticas la cual nace en el 2004 gracias a la solicitud del LanammeUCR.

Este documento incluye un resumen de cada norma INTECO relacionada a Mezclas Bituminosas, con imágenes ilustrativas del equipo y recomendaciones de profesionales del LanammeUCR para la buena práctica de dichos procesos. A su vez, incluye tres tablas comparativas en donde se demuestran las diferencias más relevantes del equipo, procedimiento y criterios de aceptación entre las normas más actualizadas de AASHTO y ASTM de mezclas bituminosas con las equivalentes a las INTECO.

Estos métodos tienen más de 7 años de no ser actualizados en Costa Rica, por lo que se invita a los anteriores miembros del comité técnico y a cualquier persona en el medio interesada a conformar un nuevo equipo de trabajo para lograr no solo actualizar dichas normas sino que también crear nuevas.
Estado del arte de la normativa técnica sobre elementos prefabricados de concreto para vivienda unifamiliar en Costa Rica
Authors: Villalobos Ramírez Francisco
Published: May 2019

En Costa Rica el sistema prefabricado de columnas y baldosas horizontales figura como una de las opciones más utilizadas en proyectos de vivienda de interés social desarrollados por el Banco Hipotecario de la vivienda, BAHNVI, este es una institución que aprueba y otorga bonos financiados por el Estado de Costa Rica para solucionar las necesidades de vivienda de sectores vulnerables de la población. Como consecuencia directa, la oferta de este producto ha aumentado considerablemente en los últimos años en la figura de pequeñas y medianas empresas distribuidas por todo el territorio nacional. Como una forma de velar por la buena calidad de estos productos se desarrolla por medio del Instituto de Normas Técnicas de Costa Rica, INTECO, la norma para elementos prefabricados de concreto para la construcción de viviendas unifamiliares de un nivel, mediante el sistema de baldosas horizontales y columnas. La primera edición de esta norma se publica en 2013 y en el mes de febrero del 2017 se publica la segunda edición, la cual expone cambios en aspectos normativos, métodos experimentales y métodos de muestreo. Desde la publicación la primera edición de la norma, se ha dado un una mejora significativa en la verificación de calidad de este producto y un desarrollo importante en trabajos de investigación en el tema. Este artículo describe las principales investigaciones nacionales desarrolladas en el tema y su relación con la evolución de la normativa técnica.
RODRIGO FACIO Y SU GENUINO PENSAMIENTO HUMANISTA EN LA UNIVERSIDAD
Authors: Cerdas Prado Emmanuel
Published: May 2019

Este ensayo consiste en estudiar el pensamiento humanista del Rodrigo Facio desde la perspectiva de un estudiante. En este sintético ensayo se explica su apor te a la vida universitaria, a la concepción de la educación superior y como estatista en la constituyente de 1949, la cual ha marcado la vida de los costarricenses. En conmemoración de sus cien años de nacimiento, se le da la oportunidad a un estudiante, en un certamen de ensayo, de profundizar en su humanismo para definir desde los tiempos recientes el baluarte de aquélhombre al modelo universitario actual. El sistema universitario necesita tener como referencia para las personas jóvenes figuras como Rodrigo Facio, fomentando la transmisión académica de una juventud activa e interesada por la realidad del país.
Colaboradores
Authors: 160 Colaboradores
Published: May 2019

Resumen biográfico
JÓVENES ANTISOCIALES O CON TENDENCIAS SEGÚN LAS PRECEPTORÍAS MEXIQUENSES
Authors: Osorio Ballesteros Abraham , Tinoco-García Alicia
Published: May 2019

En este artículo se analizan algunas ideas de las autoridades de las preceptorías del Estado de México para explicar la existencia de jóvenes con conductas antisociales entre los sectores populares, con base en una investigación cualitativa realizada en el año 2016. Se destaca que tales autoridades consideran que estos jóvenes se orientan hacia tales conductas, tanto por cambios personales como por situaciones sociales que enfrentan, otorgándole la responsabilidad a ellos y a sus familias, sin considerar los factores estructurales.
LA CIENCIA QUE CUENTA ES LA QUE SE CUENTA: LA RELACIÓN PERSONAL INVESTIGADOR-PERSONAL PERIODÍSTICO
Authors: Castillo Vargas Andrés
Published: May 2019

El objetivo principal del presente artículo es describir la valoración que el personal investigador posee del personal periodístico, a partir de un estudio descriptivo a personal investigador de 25 centros e institutos de investigación de la Universidad de Costa Rica. Los resultados evidencian actitudes y percepciones vinculares que pueden ser mejoradas en beneficio de la progresividad del conocimiento científico y la comunicabilidad de la ciencia. En este sentido, es necesario que el personal investigador identifique las habilidades y los puntos de encuentro que renueven el vínculo entre ambas profesiones, con miras a comprender mejor el engranaje que representan los procesos de comunicación pública de la ciencia.