Abraham Alvarado - Academia.edu (original) (raw)
Papers by Abraham Alvarado
Pediatric Neurosurgery
Introduction: Optimal material and timing of cranioplasty in the pediatric population continue to... more Introduction: Optimal material and timing of cranioplasty in the pediatric population continue to be debated. Autologous and alloplastic materials have various indications for use and risk factors for complications. Methods: A single-center retrospective cohort study was undertaken of all pediatric patients who underwent cranioplasty with any material from 1991–2021. Results: 149 cranioplasty implants were included. Younger age (6 years old or under), a diagnosis of craniosynostosis as reason for implant, use of autologous bone, and shorter times to cranioplasty were predictive of need for revision surgery. No factors studied had a statistically significant impact on rate of removal of implant at time of revision surgery. Conclusion: Autologous and alloplastic cranioplasty materials both have good outcomes with low rates of revision surgery in the pediatric population. Alloplastic implants may be considered in the setting of infection as reason for craniectomy given the lower rate o...
Carbohydrate Polymers, 2007
A new PCP tri-block copolymer consisting of poly (e-caprolactone)-b-chitooligosaccharide-b-poly(e... more A new PCP tri-block copolymer consisting of poly (e-caprolactone)-b-chitooligosaccharide-b-poly(ethylene glycol) (PCL-b-COS-b-PEG, PCP) was synthesized and characterized. The potential for delivering doxorubicin (DOX), a model drug, with or without genipin crosslinking was evaluated. The PCP copolymers were analyzed by Fourier-transform infrared spectrometry (FT-IR) to confirm the amine and ester groups of the COS and the PCL of the copolymer, respectively. 1 H nuclear magnetic resonance (1 H NMR) was performed to determine the structure of the PCP copolymer for demonstrating both PCL and PEG blocks grafted onto the COS block. Moreover, gel permeation chromatography (GPC) was applied to determine the number average molecular weight of the tri-block copolymer (M n), which was 11,340 Da/mole. The PCP form polymeric micelles at the critical micelle concentration (CMC) of 0.0107 wt% (or 1.0 lM) with the mean diameter 90 nm, as determined by a dynamic light-scattering (DLS) analyzer. Since PCP micelles contain COS, the zeta potentials of the micelles are changed from a neutral (e.g., À3.2 ± 1.3 mV at pH 7.4) to a cationic state (13.9 ± 4.4 mV at pH 3.0) when pH values of the suspension medium are varied. This change is a unique property of the micelles. In addition, drug delivery behavior of the PCP micelles is influenced by genipin crosslinking COS. The DOX release period of crosslinked micelles is significantly longer than that of the non-crosslinked ones (e.g., 8 days vs. 4 days, respectively) while the burst release of DOX of crosslinked ones is significantly reduced compared with that of non-crosslinked ones. In conclusion, a new tri-block COS-containing PCP copolymer/polymeric micelle has been synthesized and characterized. Moreover, the unique properties of COS-containing PCP micelles are demonstrated by varying zeta potentials via changing pH of medium and by influencing DOX delivering behaviors after genipin crosslinking.
BioResources
Cellulosic henequen fibers were subjected to steam explosion and impregnated with polyethylene gl... more Cellulosic henequen fibers were subjected to steam explosion and impregnated with polyethylene glycol (PEG) to improve fiber-matrix compatibility in polylactic acid (PLA) composites. Through Fourier-transform infrared spectroscopy (FTIR) it was shown that the hydroxyl, methyl, and ether functional groups were increased after the steam explosion treatment. Changes in the cellulose morphology caused by the steam explosion and impregnation with PEG were observed via scanning electron microscopy (SEM). Good adhesion of the treated cellulose and the PLA matrix was observed through improvement of the tensile strength and Young’s modulus of the PLA composite. The PEG impregnated into the fiber plasticized the PLA matrix and reduced the Tg from 59 °C to 52 °C. The increase in crystallinity confirmed the cellulose fibers induced nucleation of the PLA, which resulted in greater rigidity of the PLA composites.
Journal of Craniofacial Surgery, 2021
Introduction: Craniosynostosis is the premature fusion of 1 or more cranial sutures. The presenta... more Introduction: Craniosynostosis is the premature fusion of 1 or more cranial sutures. The presentation may vary, and there are differing opinions regarding surgical indications and timing. Though increased intracranial pressure (ICP) is a well-established risk of craniosynostosis, its response to treatment is not uniform. This study aims to identify the signs and symptoms indicative of increased ICP that are most likely to improve after craniosynostosis surgery. Methods: Pre- and post-operative data were retrospectively collected from patients at our institution with syndromic and non-syndromic craniosynostosis from January 2009 to June 2020. Demographics, symptoms (headache, nausea, emesis, and lethargy), signs (visual disturbances and papilledema), and imaging characteristics (copper beaten changes), if available, were analyzed. Results: One hundred fifty-three children with craniosynostosis were identified, and 56 with preoperative symptoms met inclusion criteria. Older age was si...
Results in Chemistry, 2021
Journal of Polymer Research, 2020
In this paper we present the results of the recovery of Ni(II) ions in aqueous media using poly(a... more In this paper we present the results of the recovery of Ni(II) ions in aqueous media using poly(acrylamide-co-itaconic acid) hydrogels. The copolymer was synthetized via free radical polymerization at 30°C using the potassium persulfate and N,N,N′,N′tetramethylethylenediamine redox pair. Several methodologies were studied and compared by varying the following parameters: temperature, pH of the media, Ni(II) ion concentration and aqueous solution / xerogel weight ratio. Finally, the removal efficiency of the applications of the hydrogel and the influence of the parameters was measured. Our main result was found by swelling the hydrogel in an aqueous media with pH 13, then placed at the Ni(II) solution. With this methodology, the ion recovery performance was up to 94%, this because the polymeric matrix is saturated with a NaOH solution and the nickel ions cannot penetrate the hydrogel considerably. Thus instead of absorbing the Ni(II) ion, it reacts with the OH − ions delivered at the surface of the hydrogel, forming Ni(OH) 2 layer at the surface, which is partially absorbed.
Polymer Engineering & Science, 2019
A simple but comprehensive model considering homogeneous and micellar nucleation, coagulation, en... more A simple but comprehensive model considering homogeneous and micellar nucleation, coagulation, entry of radicals to particles and to micelles and radicals' exit from particles, is presented. The model is validated, in a starved semicontinuous heterophase polymerization of ethyl methacrylate, at three monomer addition rates. The model accurately describes the overall and instantaneous conversion, the average particle density and diameter, and the number and weight average molar masses evolutions over time. It is found that even though the average number of radicals is much smaller than 0.5, the system is not 0‐1. An empirical function was used to describe the gel effect. The homogeneous nucleation was the prevailing mechanism for particle formation and large exit rates of radicals were observed. POLYM. ENG. SCI., 60: 223–232, 2019. © 2019 Society of Plastics Engineers
Child's Nervous System, 2017
Purpose Evaluation of cervical spine injury (CSI) in children requires rapid, yet accurate assess... more Purpose Evaluation of cervical spine injury (CSI) in children requires rapid, yet accurate assessment of damage. Given concerns of radiation exposure, expert consensus advises that computed tomography (CT) should be used sparingly. However, CT can provide superior image resolution and detection of pathology. Herein, we evaluate if X-ray offers equal diagnostic accuracy compared to CT imaging in identifying CSI in children. Methods We conducted a retrospective study between October 2000 and March 2012 of pediatric patients evaluated for cervical spine injury at a level 1 trauma center. All patients included in this study were imaged with cervical spine X-rays and CT at the time of injury. Demographic information, mechanism of injury, significant versus non-significant injury (as defined by the NEXUS criteria), radiographic findings, level of the injury, presence of spinal cord injury, treatment, clinical outcome, and length of follow-up were collected. Chi-squared (χ 2) and Fisher's exact tests were used as appropriate and means and standard deviations were reported. Results We identified 1296 patients who were screened for CSI. Of those, 164 patients were diagnosed with spinal cord/ column injuries (CSI). Eighty-nine patients were excluded for only having a CT or X-ray imaging without the other modality. Thus, a total of 75 patients with CSI were included in the final cohort. Using the NEXUS definitions, 78% of patients had clinically significant injuries while 22% had nonsignificant injuries. There were no injuries detected on X-ray that were not also detected on CT. For all injuries, X-ray sensitivity was 50.7%. X-rays were more sensitive to significant injuries (62.3%) compared in non-significant injuries, which were missed on all X-rays (0%). Therefore, X-rays did not identify 24 significant cervical spine injuries (32%) as defined by NEXUS. Conclusions CT is superior to X-rays in detecting both clinically significant and insignificant cervical spine injuries. These results were not dependent on patient age or location of the injury. We recommend CT imaging in the evaluation of suspected cervical spine injuries in children. Level of evidence: III
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 1991
Using electroluminescence associated with scanning tunneling microscope in AlxGa1−xAs heterostruc... more Using electroluminescence associated with scanning tunneling microscope in AlxGa1−xAs heterostructures, we show that: (a) luminescence due to recombination can be induced within single quantum wells of dimensions down to a few nm and can also be used to image them, (b) the energy of bulk bands can be determined, and (c) transport parameters can be measured, e.g., the thermalization length and the diffusion length of minority electrons. This technique opens up new possibilities for the study and characterization of semiconductors and devices—including the possibility of studying surface states and single trapping centers associated with lattice defects, impurities, chemisorbed species, etc.
Colloid and Polymer Science, 2017
The polymerization of several alkyl methacrylates in nanoemulsions made by the phase inversion te... more The polymerization of several alkyl methacrylates in nanoemulsions made by the phase inversion temperature method is presented here. The temperature versus surfactant concentration fish-like phase diagrams for a fixed mixture of alkyl methacrylate/squalane (SQ) of 95/5 w/w, Brij 56 and water were elaborated. Reaction rates were extremely fast (ca. 100% conversion in less than 3 min), and only two reaction rate intervals were observed, which is typical of nanoemulsion polymerization. It suggests that chain transfer to monomer is the main termination mechanism. The addition of squalane inhibits monomer diffusion from small droplets to larger ones and prevents the diffusion of monomer from nonreacting droplets to reacting ones, which guarantees that each monomer droplet acted as a nanoreactor. Polymer particles have similar size than the original nanoemulsion droplets indicating that the nanodroplets act as templates for the formation of the polymer nanoparticles. Reaction rates, as well as kinetics and nanoparticle characterizations by quasielastic light scattering (QLS), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC), are reported. Spheroidal nanoparticles with similar sizes and narrow distribution were observed by TEM for poly(ethyl methacrylate), poly(butyl methacrylate), and poly(hexyl methacrylate). The large molar masses and the narrow molar mass distributions were obtained by gel permeation chromatography.
Journal of Macromolecular Science, Part B, 2016
The synthesis, by two sequential inverse microemulsion polymerizations, of interpenetrating polym... more The synthesis, by two sequential inverse microemulsion polymerizations, of interpenetrating polymer networks (IPN) formed by polyacrylamide (PAM) and poly(acrylic acid) (PAA) and
Journal of Macromolecular Science, Part A, 2015
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Journal of Macromolecular Science, Part A, 2015
Macromolecular Reaction Engineering, 2015
Ethnicity & disease, 2012
To provide a descriptive profile of the people with diabetes (PWD) who received the services of t... more To provide a descriptive profile of the people with diabetes (PWD) who received the services of the Puerto Rico Quitline (PRQ) during 2008, compared to non-diabetic people (NDP) to establish a significant statistical difference. Using a cross-sectional study methodology, the Quitline database was analyzed. Ninety-four percent of the 1,137 people who received the services of the PRQ during 2008 and completed all the interviews were included in the analysis. Frequency distributions and means calculation were performed to describe the PWD. Chi-square tests, odds ratio, t test and 95% confidence intervals were calculated to identify statistically significant differences between the PWD and NDP. Nearly 11 percent (10.9%) of the people who received the services of the PRQ during 2008 and completed all the interviews reported a diabetes diagnosis. Health conditions were reported by 95.7% of PWD vs. 62.3% of NDP (P < .01). People with diabetes were more likely to have hypertension (P <...
Journal of Nursing Education and Practice, 2013
Background: Currently there is no country, social class, or group of people worldwide that has no... more Background: Currently there is no country, social class, or group of people worldwide that has not been affected by HIV/AIDS. The HIV epidemic has been surrounded by great secrecy and ignorance that has fostered the spread of the virus. HIV/AIDS and tobacco use represent the only two major causes of death worldwide. Likewise, tobacco use is a leading cause of morbidity and mortality in people without HIV and is highly prevalent in HIV positive population. The main objective of this research is to provide an epidemiological profile of people who reported having an HIV test in their lifetime and smoke (PHHT-S) in Puerto Rico. Our secondary objectives are: 1) identify the existence of statistically significant differences between PHHT-S vs. people who have had an HIV test in their lifetime and do not smoke (PHHT-NS), and 2) determine the risk of having been in a risk situation for HIV infection among PHHT-S vs. PHHT-NS. Methods: Through a cross-sectional study methodology the analysis of 2010 database of the Puerto Rico Behavioral Risk Factor Surveillance System (PRBRFSS) was performed with the Statistical Package for the Social Sciences (SPSS). In the first part, a univariate analysis was performed using frequency distributions and percentages for categorical variables and means and standard deviation calculation for continuous variables. In the second part through a bivariate analysis, smokers and non-smokers who have had an HIV test in their lifetime were compared using chi-square tests, Odds Ratio and 95% confidence intervals (CI). Results: Among the 43.2% (1,009,587) of the Puerto Ricans of 18 years and over who reported having an HIV test in their lifetime, 16.6% (167,242) reported being smokers. This study provides statistically significant data to support the existence of differences between PHHT-S and PHHT-NS, especially in the area of risk behaviors related to HIV. PHHT-S are 2.24 times more likely to engage in some risky behavior that can lead them become infected with HIV in comparison with the PHHT-NS. Conclusions: This study provides strong evidence that confirm the need for collaboration between the Tobacco Control Programs and HIV programs to implement new strategies to promote a greater number of people who smoke get tested for HIV and to influence public policy and systems change.
Protein Misfolding, Aggregation, and Conformational Diseases, 2007
Light-chain amyloidosis (AL) is characterized by the clonal expansion of plasma B cells that secr... more Light-chain amyloidosis (AL) is characterized by the clonal expansion of plasma B cells that secrete large amounts of monoclonal immunoglobulin light chains. The free light chains circulate in serum and form amyloid fibrils on vital organs such as the kidney, heart, and liver causing organ ...
Pediatric Neurosurgery
Introduction: Optimal material and timing of cranioplasty in the pediatric population continue to... more Introduction: Optimal material and timing of cranioplasty in the pediatric population continue to be debated. Autologous and alloplastic materials have various indications for use and risk factors for complications. Methods: A single-center retrospective cohort study was undertaken of all pediatric patients who underwent cranioplasty with any material from 1991–2021. Results: 149 cranioplasty implants were included. Younger age (6 years old or under), a diagnosis of craniosynostosis as reason for implant, use of autologous bone, and shorter times to cranioplasty were predictive of need for revision surgery. No factors studied had a statistically significant impact on rate of removal of implant at time of revision surgery. Conclusion: Autologous and alloplastic cranioplasty materials both have good outcomes with low rates of revision surgery in the pediatric population. Alloplastic implants may be considered in the setting of infection as reason for craniectomy given the lower rate o...
Carbohydrate Polymers, 2007
A new PCP tri-block copolymer consisting of poly (e-caprolactone)-b-chitooligosaccharide-b-poly(e... more A new PCP tri-block copolymer consisting of poly (e-caprolactone)-b-chitooligosaccharide-b-poly(ethylene glycol) (PCL-b-COS-b-PEG, PCP) was synthesized and characterized. The potential for delivering doxorubicin (DOX), a model drug, with or without genipin crosslinking was evaluated. The PCP copolymers were analyzed by Fourier-transform infrared spectrometry (FT-IR) to confirm the amine and ester groups of the COS and the PCL of the copolymer, respectively. 1 H nuclear magnetic resonance (1 H NMR) was performed to determine the structure of the PCP copolymer for demonstrating both PCL and PEG blocks grafted onto the COS block. Moreover, gel permeation chromatography (GPC) was applied to determine the number average molecular weight of the tri-block copolymer (M n), which was 11,340 Da/mole. The PCP form polymeric micelles at the critical micelle concentration (CMC) of 0.0107 wt% (or 1.0 lM) with the mean diameter 90 nm, as determined by a dynamic light-scattering (DLS) analyzer. Since PCP micelles contain COS, the zeta potentials of the micelles are changed from a neutral (e.g., À3.2 ± 1.3 mV at pH 7.4) to a cationic state (13.9 ± 4.4 mV at pH 3.0) when pH values of the suspension medium are varied. This change is a unique property of the micelles. In addition, drug delivery behavior of the PCP micelles is influenced by genipin crosslinking COS. The DOX release period of crosslinked micelles is significantly longer than that of the non-crosslinked ones (e.g., 8 days vs. 4 days, respectively) while the burst release of DOX of crosslinked ones is significantly reduced compared with that of non-crosslinked ones. In conclusion, a new tri-block COS-containing PCP copolymer/polymeric micelle has been synthesized and characterized. Moreover, the unique properties of COS-containing PCP micelles are demonstrated by varying zeta potentials via changing pH of medium and by influencing DOX delivering behaviors after genipin crosslinking.
BioResources
Cellulosic henequen fibers were subjected to steam explosion and impregnated with polyethylene gl... more Cellulosic henequen fibers were subjected to steam explosion and impregnated with polyethylene glycol (PEG) to improve fiber-matrix compatibility in polylactic acid (PLA) composites. Through Fourier-transform infrared spectroscopy (FTIR) it was shown that the hydroxyl, methyl, and ether functional groups were increased after the steam explosion treatment. Changes in the cellulose morphology caused by the steam explosion and impregnation with PEG were observed via scanning electron microscopy (SEM). Good adhesion of the treated cellulose and the PLA matrix was observed through improvement of the tensile strength and Young’s modulus of the PLA composite. The PEG impregnated into the fiber plasticized the PLA matrix and reduced the Tg from 59 °C to 52 °C. The increase in crystallinity confirmed the cellulose fibers induced nucleation of the PLA, which resulted in greater rigidity of the PLA composites.
Journal of Craniofacial Surgery, 2021
Introduction: Craniosynostosis is the premature fusion of 1 or more cranial sutures. The presenta... more Introduction: Craniosynostosis is the premature fusion of 1 or more cranial sutures. The presentation may vary, and there are differing opinions regarding surgical indications and timing. Though increased intracranial pressure (ICP) is a well-established risk of craniosynostosis, its response to treatment is not uniform. This study aims to identify the signs and symptoms indicative of increased ICP that are most likely to improve after craniosynostosis surgery. Methods: Pre- and post-operative data were retrospectively collected from patients at our institution with syndromic and non-syndromic craniosynostosis from January 2009 to June 2020. Demographics, symptoms (headache, nausea, emesis, and lethargy), signs (visual disturbances and papilledema), and imaging characteristics (copper beaten changes), if available, were analyzed. Results: One hundred fifty-three children with craniosynostosis were identified, and 56 with preoperative symptoms met inclusion criteria. Older age was si...
Results in Chemistry, 2021
Journal of Polymer Research, 2020
In this paper we present the results of the recovery of Ni(II) ions in aqueous media using poly(a... more In this paper we present the results of the recovery of Ni(II) ions in aqueous media using poly(acrylamide-co-itaconic acid) hydrogels. The copolymer was synthetized via free radical polymerization at 30°C using the potassium persulfate and N,N,N′,N′tetramethylethylenediamine redox pair. Several methodologies were studied and compared by varying the following parameters: temperature, pH of the media, Ni(II) ion concentration and aqueous solution / xerogel weight ratio. Finally, the removal efficiency of the applications of the hydrogel and the influence of the parameters was measured. Our main result was found by swelling the hydrogel in an aqueous media with pH 13, then placed at the Ni(II) solution. With this methodology, the ion recovery performance was up to 94%, this because the polymeric matrix is saturated with a NaOH solution and the nickel ions cannot penetrate the hydrogel considerably. Thus instead of absorbing the Ni(II) ion, it reacts with the OH − ions delivered at the surface of the hydrogel, forming Ni(OH) 2 layer at the surface, which is partially absorbed.
Polymer Engineering & Science, 2019
A simple but comprehensive model considering homogeneous and micellar nucleation, coagulation, en... more A simple but comprehensive model considering homogeneous and micellar nucleation, coagulation, entry of radicals to particles and to micelles and radicals' exit from particles, is presented. The model is validated, in a starved semicontinuous heterophase polymerization of ethyl methacrylate, at three monomer addition rates. The model accurately describes the overall and instantaneous conversion, the average particle density and diameter, and the number and weight average molar masses evolutions over time. It is found that even though the average number of radicals is much smaller than 0.5, the system is not 0‐1. An empirical function was used to describe the gel effect. The homogeneous nucleation was the prevailing mechanism for particle formation and large exit rates of radicals were observed. POLYM. ENG. SCI., 60: 223–232, 2019. © 2019 Society of Plastics Engineers
Child's Nervous System, 2017
Purpose Evaluation of cervical spine injury (CSI) in children requires rapid, yet accurate assess... more Purpose Evaluation of cervical spine injury (CSI) in children requires rapid, yet accurate assessment of damage. Given concerns of radiation exposure, expert consensus advises that computed tomography (CT) should be used sparingly. However, CT can provide superior image resolution and detection of pathology. Herein, we evaluate if X-ray offers equal diagnostic accuracy compared to CT imaging in identifying CSI in children. Methods We conducted a retrospective study between October 2000 and March 2012 of pediatric patients evaluated for cervical spine injury at a level 1 trauma center. All patients included in this study were imaged with cervical spine X-rays and CT at the time of injury. Demographic information, mechanism of injury, significant versus non-significant injury (as defined by the NEXUS criteria), radiographic findings, level of the injury, presence of spinal cord injury, treatment, clinical outcome, and length of follow-up were collected. Chi-squared (χ 2) and Fisher's exact tests were used as appropriate and means and standard deviations were reported. Results We identified 1296 patients who were screened for CSI. Of those, 164 patients were diagnosed with spinal cord/ column injuries (CSI). Eighty-nine patients were excluded for only having a CT or X-ray imaging without the other modality. Thus, a total of 75 patients with CSI were included in the final cohort. Using the NEXUS definitions, 78% of patients had clinically significant injuries while 22% had nonsignificant injuries. There were no injuries detected on X-ray that were not also detected on CT. For all injuries, X-ray sensitivity was 50.7%. X-rays were more sensitive to significant injuries (62.3%) compared in non-significant injuries, which were missed on all X-rays (0%). Therefore, X-rays did not identify 24 significant cervical spine injuries (32%) as defined by NEXUS. Conclusions CT is superior to X-rays in detecting both clinically significant and insignificant cervical spine injuries. These results were not dependent on patient age or location of the injury. We recommend CT imaging in the evaluation of suspected cervical spine injuries in children. Level of evidence: III
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 1991
Using electroluminescence associated with scanning tunneling microscope in AlxGa1−xAs heterostruc... more Using electroluminescence associated with scanning tunneling microscope in AlxGa1−xAs heterostructures, we show that: (a) luminescence due to recombination can be induced within single quantum wells of dimensions down to a few nm and can also be used to image them, (b) the energy of bulk bands can be determined, and (c) transport parameters can be measured, e.g., the thermalization length and the diffusion length of minority electrons. This technique opens up new possibilities for the study and characterization of semiconductors and devices—including the possibility of studying surface states and single trapping centers associated with lattice defects, impurities, chemisorbed species, etc.
Colloid and Polymer Science, 2017
The polymerization of several alkyl methacrylates in nanoemulsions made by the phase inversion te... more The polymerization of several alkyl methacrylates in nanoemulsions made by the phase inversion temperature method is presented here. The temperature versus surfactant concentration fish-like phase diagrams for a fixed mixture of alkyl methacrylate/squalane (SQ) of 95/5 w/w, Brij 56 and water were elaborated. Reaction rates were extremely fast (ca. 100% conversion in less than 3 min), and only two reaction rate intervals were observed, which is typical of nanoemulsion polymerization. It suggests that chain transfer to monomer is the main termination mechanism. The addition of squalane inhibits monomer diffusion from small droplets to larger ones and prevents the diffusion of monomer from nonreacting droplets to reacting ones, which guarantees that each monomer droplet acted as a nanoreactor. Polymer particles have similar size than the original nanoemulsion droplets indicating that the nanodroplets act as templates for the formation of the polymer nanoparticles. Reaction rates, as well as kinetics and nanoparticle characterizations by quasielastic light scattering (QLS), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC), are reported. Spheroidal nanoparticles with similar sizes and narrow distribution were observed by TEM for poly(ethyl methacrylate), poly(butyl methacrylate), and poly(hexyl methacrylate). The large molar masses and the narrow molar mass distributions were obtained by gel permeation chromatography.
Journal of Macromolecular Science, Part B, 2016
The synthesis, by two sequential inverse microemulsion polymerizations, of interpenetrating polym... more The synthesis, by two sequential inverse microemulsion polymerizations, of interpenetrating polymer networks (IPN) formed by polyacrylamide (PAM) and poly(acrylic acid) (PAA) and
Journal of Macromolecular Science, Part A, 2015
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Journal of Macromolecular Science, Part A, 2015
Macromolecular Reaction Engineering, 2015
Ethnicity & disease, 2012
To provide a descriptive profile of the people with diabetes (PWD) who received the services of t... more To provide a descriptive profile of the people with diabetes (PWD) who received the services of the Puerto Rico Quitline (PRQ) during 2008, compared to non-diabetic people (NDP) to establish a significant statistical difference. Using a cross-sectional study methodology, the Quitline database was analyzed. Ninety-four percent of the 1,137 people who received the services of the PRQ during 2008 and completed all the interviews were included in the analysis. Frequency distributions and means calculation were performed to describe the PWD. Chi-square tests, odds ratio, t test and 95% confidence intervals were calculated to identify statistically significant differences between the PWD and NDP. Nearly 11 percent (10.9%) of the people who received the services of the PRQ during 2008 and completed all the interviews reported a diabetes diagnosis. Health conditions were reported by 95.7% of PWD vs. 62.3% of NDP (P < .01). People with diabetes were more likely to have hypertension (P <...
Journal of Nursing Education and Practice, 2013
Background: Currently there is no country, social class, or group of people worldwide that has no... more Background: Currently there is no country, social class, or group of people worldwide that has not been affected by HIV/AIDS. The HIV epidemic has been surrounded by great secrecy and ignorance that has fostered the spread of the virus. HIV/AIDS and tobacco use represent the only two major causes of death worldwide. Likewise, tobacco use is a leading cause of morbidity and mortality in people without HIV and is highly prevalent in HIV positive population. The main objective of this research is to provide an epidemiological profile of people who reported having an HIV test in their lifetime and smoke (PHHT-S) in Puerto Rico. Our secondary objectives are: 1) identify the existence of statistically significant differences between PHHT-S vs. people who have had an HIV test in their lifetime and do not smoke (PHHT-NS), and 2) determine the risk of having been in a risk situation for HIV infection among PHHT-S vs. PHHT-NS. Methods: Through a cross-sectional study methodology the analysis of 2010 database of the Puerto Rico Behavioral Risk Factor Surveillance System (PRBRFSS) was performed with the Statistical Package for the Social Sciences (SPSS). In the first part, a univariate analysis was performed using frequency distributions and percentages for categorical variables and means and standard deviation calculation for continuous variables. In the second part through a bivariate analysis, smokers and non-smokers who have had an HIV test in their lifetime were compared using chi-square tests, Odds Ratio and 95% confidence intervals (CI). Results: Among the 43.2% (1,009,587) of the Puerto Ricans of 18 years and over who reported having an HIV test in their lifetime, 16.6% (167,242) reported being smokers. This study provides statistically significant data to support the existence of differences between PHHT-S and PHHT-NS, especially in the area of risk behaviors related to HIV. PHHT-S are 2.24 times more likely to engage in some risky behavior that can lead them become infected with HIV in comparison with the PHHT-NS. Conclusions: This study provides strong evidence that confirm the need for collaboration between the Tobacco Control Programs and HIV programs to implement new strategies to promote a greater number of people who smoke get tested for HIV and to influence public policy and systems change.
Protein Misfolding, Aggregation, and Conformational Diseases, 2007
Light-chain amyloidosis (AL) is characterized by the clonal expansion of plasma B cells that secr... more Light-chain amyloidosis (AL) is characterized by the clonal expansion of plasma B cells that secrete large amounts of monoclonal immunoglobulin light chains. The free light chains circulate in serum and form amyloid fibrils on vital organs such as the kidney, heart, and liver causing organ ...