University of Puerto Rico at Mayagüez
Recent publications
Let $\Omega\subseteq\mathbb{R\!}^N$ be a bounded Lipschitz domain with the $W^{1,\overset{\rightarrow} p(\cdot)}$-extension property, for $N\geq3$. We investigate the solvability and global regularity of a class of quasi-linear elliptic equations involving the anisotropic $\overset{\rightarrow}p(\cdot)$-Laplace operator $\Delta_{\overset{\rightarrow}p(\cdot)}$, with nonhomogeneous anisotropic Wentzell boundary conditions $$\displaystyle\sum^N_{i=1}|\nabla u|^{p_i(\cdot)-2}\displaystyle\frac{\partial u}{\partial x_i}\nu_i- \Delta_{_{\overset{\rightarrow}q(\cdot),\Gamma}}u+ \beta|u|^{q_M(\cdot)-2}u\,\ni\,0\,\,\,\,\,\textrm{on}\,\,\,\Gamma:=\partial\Omega,$$ for $\beta\in L^{\infty}(\Gamma)^+$ with a positive lower bound, where $\overset{\rightarrow} p\in C^{0,1}(\overline{\Omega})^N$ and $\overset{\rightarrow} q\in C^{0,1}(\Gamma)^{N-1}$ fulfill $1< p^-_m\leq p^+_M<\infty$, and $1< q^-_m\leq q^+_M<\infty$. Here $\Delta_{_{\overset{\rightarrow}q(\cdot),\Gamma}}$ denotes the anisotropic $\overset{\rightarrow}q(\cdot)$-Laplace-Beltrami operator. We first show existence and uniqueness of weak solutions for the elliptic problem, and moreover, we prove that such solutions are globally bounded over $\overline{\Omega}$. Key $L^{\infty}$-type a priori estimates for the difference of weak solutions are provided, as well as Maximum principles and inverse positivity results. At the end, we establish a sort of "nonlinear anisotropic Fredholm alternative" for the corresponding anisotropic Wentzell problem of nonstandard structure.
We conducted a scientific literature review, and a comprehensive analysis based on international fisheries databases, for dolphinfish (Coryphaena hippurus) from the Western Central Atlantic Ocean (WCA) from 1950 to 2018. This analysis updated the dolphinfish catch and efforts trends in comparison to those calculated in Mahon (1999), the first regional catch review for the species that was conducted with data from the 1950s through the mid-1990s. Results showed that the commercial pelagic longline effort doubled within, and quadrupled outside, of national jurisdictions. Commercial landings increased nearly three-fold, but 23 nations still do not report explicit dolphinfish landings to the FAO yet are known to catch dolphinfish. In the WCA, the US Atlantic recreational fishery represents the largest reporting sector by two-fold. When combined with reported commercial landings for 2016, total direct dolphinfish catch was 14,110 metric tons, of which 62 % was estimated to be recreational catch. Since the first regional fishery analysis of dolphinfish, the uncertainty of the status of the fishery has increased with several nations reporting higher landings of unidentified marine fish species. Also, new burgeoning social (e.g., FAD programs) and environmental processes (e.g., Sargassum blooms) lead to the presumption that higher amounts of juvenile dolphinfish are caught throughout the region. First reports of consequential amounts of dolphinfish bycatch have been documented in the pelagic longline fisheries, as well as the first modeled and anecdotal evidence of stock decline has been suggested. Results stress the immediate need for WCA nations to adopt a precautionary approach for proper fishery management of dolphinfish throughout the WCA, not only to increase spawning biomass but also for overall stock health and its conservation.
Environmental contamination with Cadmium (Cd) is of great concern due to its hazardous effects on living organisms.Query In the present research, Leucaena leucocephala plants were exposed to Cd concentrations of 5, 10, and 15 mg/L to determine their potential use in Cd remediation. Different parameters including Cd uptake, macro/micronutrient content, chlorophyl, and catalase production were determined. Results indicated that Cd uptake by L. leucocephala roots did not show a significant difference between treatments. However, a significant increase in Cd content (Tukey´s HSD) was observed in stems as Cd levels in the media augmented. The highest Cd content (830 ± 20 mg/kg) was determined in stems of plants exposed to 15 mg/L Cd, and no Cd was detected in leaves. Data showed that as Cd concentration increased in the media, Ca, Mg, K, Zn, and Mn decreased. Moreover, while the presence of Cd reduced catalase activity in roots, chlorophyll production was not affected.
This paper investigates the impact of quadrature signal generation based phase-locked loop (QSG-PLL) methods on data-driven modeling of grid-connected single-phase inverters (GCSI). The magnitudes of the grid voltage and current injected by a GCSI simulated in MATLAB/Simulink are estimated by each QSG-PLL approach. The best transfer function for the GCSI model is estimated in terms of goodness of fit, using the magnitudes obtained by each approach and the instrument variable system identification approach. Different grid disturbances (e.g., voltage sag, phase angle jumps, harmonic distortions, frequency fluctuation) are used to evaluate the performance of each data-driven model in comparison to the simulated model. The paper provides researchers guidance on which QSG-PLL to use to model GCSIs using data-driven methods.
(Ba0.955Ca0.045)(Zr0.17Ti0.83)O3 [BCZT] epitaxial were grown on La0.67Sr0.33MnO3 (LSMO) coated (100)‐oriented MgO single crystal substrates by pulsed laser deposition (PLD) technique. Herein, we report crystal structure, ferroelectric, piezoresponse force microscopy (PFM) and energy storage properties near the morphotropic phase boundary (MPB) composition of [Ba0.850Ca0.15Zr0.1Ti0.90O3] solid solution. Epitaxial growth of the films was confirmed using X‐ray diffraction (XRD) spectra. Room temperature Raman spectroscopy confirms perovskite phase of BCZT films. Room temperature polarization‐electric field (P‐E) loops confirm the ferroelectric nature of BCZT films. Ferroelectric hysteresis loops demonstrate high saturation polarization (Pmax ~ 97.96 μC/cm2) and remanant polarization (Pr~70.1 μC/cm2) at an applied maximum electric field~ 2.77 MV/cm. The optimized BCZT epitaxial thin films have shown moderate dielectric properties at different measured frequencies (10 kHz–100 kHz). Nanoscale Piezoresponse Force Microscopy (PFM) images demonstrate switchable ferroelectric polarization of these thin films above ± 9V of dc voltage applied. Energy storage properties measured from ferroelectric loops revealed a high discharge curve energy density ~27.5 J/cm3 at a maximum electric field of 2.77 MV/cm. Epitaxial grown BCZT films are suitable candidate materials for capacitor applications. This article is protected by copyright. All rights reserved.
Desmoplastic fibroma is an extremely rare primary bone tumor that can mimic the presentation of other bone lesions. We describe the case of a middle-aged male with a mass on the left distal femur initially diagnosed as fibrous dysplasia that underwent a wide margin excision followed by a distal femoral replacement to restore anatomy and functionality. Histologic examination of the complete surgical specimen was consistent with a desmoplastic fibroma. This case is the first report of a successful application of endoprosthetic reconstruction after desmoplastic fibroma resection.
Early-onset scoliosis (EOS) is defined as any spinal deformity that is present before 10 years old, regardless of etiology. Deformity must be evaluated based on the intercorrelation between the lungs, spine, and thorax. Curvatures of early-onset have increased risk of progression, cardiorespiratory problems, and increased morbidity and mortality. Progression of the deformity may produce thoracic insufficiency syndrome, where a distorted thorax is unable to support normal respiratory function or lung growth. Management and treatment of EOS should pursue a holistic approach in which the psychological impact and quality of life of the patient are also taken into consideration. Growth-friendly surgical techniques have not met the initial expectations of correcting scoliotic deformity, promoting thoracic growth, and improving pulmonary function.
L-Asparaginase (ASNase) is used in medicine for neoplasms treatment and in food industry for mitigation of acrylamide in high-temperature processed food. In medicine, commercial ASNases have exhibited side effects and l-glutaminase (GLNase) activity affecting the clinical treatment. The aim of this work was to study a novel ASNase from Enterobacter sp. M55 isolated from Maras Salters in Peru, which was purified and biochemically characterised. This ASNase exhibited a Km of 5.71 mM and a Vmax of 0.16 µmol mL–1 min–1, as well as an optimum temperature and pH of 37 °C and 6, respectively. Moreover, a good activity (80 %) was observed at physiological pH. Likewise, the enzyme increased its activity by around 50% in presence of urea, glutathione, and glucose. Whilst in presence of serum compounds, it kept more that 60 % of activity. In addition, this ASNase showed low GLNase activity.
Sugarcane aphid [Melanaphis sacchari (Zehntner)] is a destructive pest that has had an economic impact on sorghum in North America since 2013. The identification, development, and use of resistant sorghum germplasm is the most feasible strategy to control the pest. Nevertheless, the genetic control of sugarcane aphid (SCA) resistance is unknown for most sorghum resistant lines. To identify the genetic regions that confer SCA resistance in sorghum line SC112‐14, 103 recombinant inbred lines (RILs) derived by its cross with the susceptible line PI 609251 were evaluated for their SCA resistance response in Georgia during two consecutive years. The resistance response was determined based on two ratings (two weeks apart) for aphid population size (APS) and aphid‐induced plant damage (APD) each year. Segregation for SCA resistance was observed for the first APS and both APD ratings, and the broad‐sense heritability estimate ranged from 0.71 to 0.76, respectively. A QTL analysis using a high‐density linkage map of 3,852 single nucleotide polymorphisms (SNPs) detected an 81 kb genomic region on chromosome 6 that explained 50 ‐ 55% of the phenotypic variation. Comparative mapping analysis found that the resistance locus in SC112‐14 is located 8 and 10 cM upstream of the Henong 16 (RMES1) and Tx2783 resistance loci, respectively, and encloses the SNP Sbv3.1_06_2316351 associated in Haitian resistant lines. Therefore, the line SC112‐14 is an additional SCA resistance source that can be combined or strategically used with other resistance sources to assure a more robust host plant resistance to the SCA. This article is protected by copyright. All rights reserved
Schistosomatidae Stiles and Hassall 1898 is a medically significant family of digenetic trematodes (Trematoda: Digenea), members of which infect mammals or birds as definitive hosts and aquatic or amphibious gastropods as intermediate hosts. Currently, there are 17 named genera, for many of which evolutionary interrelationships remain unresolved. The lack of a resolved phylogeny has encumbered our understanding of schistosomatid evolution, specifically patterns of host-use and the role of host-switching in diversification. Here, we used targeted sequence capture of ultra-conserved elements (UCEs) from representatives of 13 of the 17 named genera and 11 undescribed lineages that are presumed to represent either novel genera or species to generate a phylogenomic dataset for the estimation of schistosomatid interrelationships. This study represents the largest phylogenetic effort within the Schistosomatidae in both the number of loci and breadth of taxon sampling. We present a near-comprehensive family-level phylogeny providing resolution to several clades of long-standing uncertainty within Schistosomatidae, including resolution for the placement of the North American mammalian schistosomes, implying a second separate capture of mammalian hosts. Additionally, we present evidence for the placement of Macrobilharzia at the base of the Schistosoma + Bivitellobilharzia radiation. Patterns of definitive and intermediate host use and a strong role for intermediate host-switching are discussed relative to schistosomatid diversification.
This study examines how brand communication influences consumer‐based brand equity through social networking sites in the presence of brand attachment as a mediator. The outcomes related to consumer‐based brand equity, such as consumers' pay intention and loyalty to a brand and a brand's vocal ability, are also explored in this study. An empirical investigation for 498 responses was carried using Smart‐PLS, Process‐Macro & Artificial Neural Network modeling (ANN) based hybrid approach. The analysis indicates that brand consumer‐based brand equity is high when a brand's communication on social media platforms is positive. A strong mediating role of brand attachment is confirmed. The study is unique in terms of explaining the role of brand communication on Social Networking Sites (SNSs) and its impact on consumer‐based brand equity in the presence of brand attachment as a mediator. While focusing on Millennials' tech‐savvy characteristics and considering SNSs as an advanced tool for brand communication, brands should refine their marketing strategy.
Prior studies on the in‐store experience focus on the impact of store atmosphere. Sensory marketing and brand experience, on the other hand, have been found to be significant in providing a better consumer experience in recent studies. Thus, the goal of this paper is to broaden the scope of this study by examining the causal effect of sensory marketing cues and brand experience on emotional attachment, and subsequent brand loyalty in a luxury retail store setting. We also studied the moderating role of store image in the relationships. To this end, the three separate but related studies (Study 1, N = 409, Study 2, N = 294, Study 3, N = 139) were conducted. Study 1 shows that sensory marketing cues positively contribute to enhancing the luxury retail brand experiences. Both sensory marketing and brand experiences appeared promising in increasing emotional attachment and subsequent brand loyalty. Study 2 findings further suggest that sensory marketing cues and brand experience interact significantly with store image to improve consumers' emotional attachment with luxury brands. Study 3 replicated the pattern observed in Studies 1 and 2 and further suggested that consumers in the luxury store setting expressed stronger emotional attachment and brand loyalty than consumers in the nonluxury store environment.
Solid acid composite electrolytes RbH2PO4/LaPO4 were prepared with the molar percentage ratio and observed the structural, thermal, and transport properties. The superprotonic phase transition was identified in RbH2PO4 at 250 °C. The outstanding performance of RbH2PO4 was enhanced due to the addition of LaPO4 in the form of conductivity and stability. An enhancement in conductivity of 3–5 orders of magnitude was found at high temperatures compared to low temperatures in composite electrolytes. Thermal characterization showed that by introducing the additives, the dehydration behavior in DSC at higher temperatures shifted to lower. The minimum weight loss of composite indicates stability with LaPO4. Stable protonic conductivity for RbH2PO4 and composites was observed in a hermetically closed chamber and also under highly humidified conditions. The ionic conductivity and thermal stability of RbH2PO4/LaPO4 is the key point of our study that lays the foundation for the study of the solid electrolytes composites mechanism.
Coral‐reef degradation is driving global‐scale reductions in reef‐building capacity and the ecological, geological, and socioeconomic functions it supports. The persistence of those essential functions will depend on whether coral‐reef management is able to rebalance the competing processes of reef accretion and erosion. Here, we reconstructed census‐based carbonate budgets of 46 reefs throughout the Florida Keys from 1996 to 2019. We evaluated the environmental and ecological drivers of changing budget states and compared historical trends in reef‐accretion potential to millennial‐scale baselines of accretion from reef cores and future projections with coral restoration. We found that historically, most reefs had positive carbonate budgets, and many had reef‐accretion potential comparable to the ~3 mm year−1 average accretion rate during the peak of regional reef building ~7000 years ago; however, declines in reef‐building Acropora palmata and Orbicella spp. corals following a series of thermal stress events and coral disease outbreaks resulted in a shift from positive to negative budgets for most reefs in the region. By 2019, only ~15% of reefs had positive net carbonate production. Most of those reefs were in inshore, Lower Keys patch‐reef habitats with low water clarity, supporting the hypothesis that environments with naturally low irradiance may provide a refugia from thermal stress. We caution that our estimated carbonate budgets are likely overly optimistic; comparison of reef‐accretion potential to measured accretion from reef cores suggests that, by not accounting for the role of nonbiological physical and chemical erosion, census‐based carbonate budgets may underestimate total erosion by ~1 mm year−1 (−1.15 kg CaCO3 m−2 year−1). Although the present state of Florida's reefs is dire, we demonstrate that the restoration of reef‐building corals has the potential to help mitigate declines in reef accretion in some locations, which could allow some key ecosystem functions to be maintained until the threat of global climate change is addressed. We used carbonate budgets to reconstruct reef‐accretion potential at 46 reefs throughout the Florida Keys from 1996–2019. Whereas in 1996 many reefs grew at rates comparable with millennial‐scale baselines from reef cores, over the next two decades, thermal stress drove substantial losses of reef‐building corals. As a result, erosion is now the dominant process on most reefs in the region. Although the present state of Florida’s reefs appears dire, we demonstrate that coral restoration has the potential to reverse long‐term declines in reef growth on a local scale and preserve key reef functions until global‐scale threats are mitigated.
The vulnerability of fish spawning aggregations (FSA) to fishing pressure has led to seasonal fishing bans for certain aggregating reef-fish species and seasonal or permanent closures of known FSA sites throughout the Caribbean. While discerning the degree of compliance with fisheries regulations is essential in evaluating their success, this information can be scarce when opportunistic surveillance from enforcement vessels is minimal or absent. We used passive acoustic recorders to determine the temporal patterns of vessel activity at three red hind, Epinephelus guttatus, spawning aggregation sites off western Puerto Rico with varying levels of protection (Buoy 4: no regulation, Abrir la Sierra (ALS): seasonal closure, and Mona: permanent closure) during the closed (January and February) and open (March) periods for the capture of red hind. We proposed that dynamic vessel sounds (e.g., gear shifting, sudden changes in speed) at known FSA sites and during aggregating periods could be indicative of fishing activity. A band-limited energy detector was used to detect vessel sounds, with detections grouped into discreate vessel events and classified as having only constant vessel sounds or containing dynamic vessel sounds. While most of the vessel events consisted of constant vessel sounds at all sites, events with dynamic vessel sounds were greatest at Buoy 4, followed by ALS and only one detected at Mona. Average events with dynamic vessel sounds were greater during the closed than the open period at Buoy 4, while the opposite was found at ALS, and red hind calling activity was significantly correlated with vessel detections during 3 years at Buoy 4. Results suggest fishers may have been targeting red hind at Buoy 4 despite red hind's seasonal closure, and the site-specific regulations at ALS may have served as a deterrent and divert fishing effort towards other areas. Acoustic records can reveal high-resolution temporal patterns of vessel activity and of events with dynamic vessel sounds, which could be used to infer about fishing activities and complement other surveys to provide estimates of compliance.
Sampling-based motion planning (SBMP) is a major algorithmic trajectory planning approach in autonomous driving given its high efficiency and outstanding performance in practice. However, driving safety still calls for further refinement of SBMP. In this article we organically integrate algorithmic motion planning with learning models to improve SBMP in highway traffic scenarios from the following two perspectives. First, given the number of points to be sampled, we develop a new model to sample “important” points for SBMP by predicting the intention of surrounding vehicles and learning the distribution of human drivers’ trajectory. Second, we empirically study the relationship between the number of sample points and the environment, which is largely ignored in conventional SBMP. Then, we provide a guideline to select the appropriate number of points to be sampled under different scenarios to guarantee efficiency. The simulation experiments are conducted based on the vehicle trajectory dataset NGSIM. The results show that the proposed sampling strategy outperforms existing sampling strategies in terms of the computing time, traveling time, and smoothness of the trajectory.
In variographic analysis the nugget effect provides an estimate of the total process measurement system error. The value of variographic analysis can be further increased by differentiating the analytical error from the sampling errors. The ratio of the minimum practical error (MPE) to the analytical error provides an estimate of the suitability and performance of a sampling system since the analytical error would still remain even if sampling errors could be completely eliminated. The sampling and analytical errors for four systems used to obtain 1-D lots of pharmaceutical powder blends is presented. The first studies were conducted with blends moving over a conveyor belt and with the feed-frame of a tablet press. The researchers then developed and patented a new stream sampler and chute for sampling and analysis of pharmaceutical powder blends. Near Infrared or Raman spectra were obtained as the powder blends flowed or moved and used to determine the drug concentration in the blends. Even though these methods do not require sample extraction and sample preparation in a laboratory, they are still subject to sampling errors which were estimated through the variographic analysis. The MPE was compared to the analytical error for these four systems. The results obtained show that it is often possible to reduce sampling errors to less than ten times the analytical error. These studies represent the first efforts to estimate and reduce sampling errors in the analysis of the powder blends used to manufacture the tablets that many patients take daily.
Background : People Who Inject Drugs (PWID) are at a higher risk of acquiring bloodborne infections. This study aimed to estimate the prevalence of Hepatitis C Virus (HCV) in People Who Inject Drugs (PWID) and identify correlates and risk factors using data from the Puerto Rico National HIV Behavioral System, PWID cycle 5 conducted in 2018. Methods : A total of 502 San Juan Metropolitan Statistical Area participants were recruited through Respondent Driven Sampling method. Sociodemographic, health-related, and behavioral characteristics were assessed. Detection of HCV antibodies was completed after the face-to-face survey. Descriptive and logistic regression analyses were performed using STATA 17™. Results : The prevalence of HCV was 76.5% (95%CI: 70.8%-81.4%). Adjusted multivariate logistic regression models showed that frequent speedball injectors and knowing the HCV serostatus of the last sharing partner were significantly more associated with HCV infection (OR a = 4.17; 95% CI: 1.40-12.42; OR a = 4.49; 95% CI: 1.43-14.09, respectively). Conclusions : A high prevalence of HCV infection in PWID was observed in this sample, validating the continuing call for local action for public health and prevention strategies.
View Video Presentation: Lagrangian Coherent Structures (LCS) have recently received a significant attention due to its advantages over Eulerian coherent structure identification schemes. Transport barriers and transport enhancers as material surfaces are identified by LCS techniques and can be used to analyze turbulent mixing in many engineering applications. This study utilized high-fidelity Direct Numerical Simulation (DNS) databases of spatially-developing turbulent boundary layers (SDTBL) at the incompressible, supersonic (Mach = 2.5), and hypersonic (Mach = 5) flow regimes. The main purpose is to qualitatively study the effects of flow compressibility and Reynolds number on LCS. Compressibility effects on turbulent coherent structures were observed to be weak, becoming more noticeable in the hypersonic regime for low Reynolds cases. Furthermore, the presence of hairpin vortices was scarce beyond y+ = 100 (i.e., in the log-wake region) of hypersonic turbulent boundary layers. In contrast, the Reynolds number dependency on LCS was evident given by the high level of isotropization of turbulent coherent structures. Moreover, strong compressibility effects were observed once the Reynolds number was increased. This resulted in more abundant and more isotropic structures for high Reynolds supersonic flow.
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5,396 members
Mauricio Cabrera-Rios
  • Department of Industrial Engineering
Sandra Cruz-Pol
  • Department of Electrical and Computer Engineering
Eduardo Schroder
  • Departamento de Ciencias Agroambientales
Paul Sundaram
  • Department of Mechanical Engineering
Dimuth Siritunga
  • Departamento de Biología
Call Box 9000, 00681, Mayagüez, Puerto Rico