Daniel Pérez gomez - Academia.edu (original) (raw)

Papers by Daniel Pérez gomez

there was a 30% lower risk of sPTB in a subsequent delivery if the second stage of labor length w... more there was a 30% lower risk of sPTB in a subsequent delivery if the second stage of labor length was between 55-96 minutes in the first term delivery (Table 3). There were no differences in sPTB when stratified by mode of delivery.

Journal of Nonlinear Science, 2021

The structure, linear stability, and dynamics of localized solutions to singularly perturbed reac... more The structure, linear stability, and dynamics of localized solutions to singularly perturbed reaction-diffusion equations has been the focus of numerous rigorous, asymptotic, and numerical studies in the last few decades. However, with a few exceptions, these studies have often assumed homogeneous boundary conditions. Motivated by the recent focus on the analysis of bulksurface coupled problems we consider the effect of inhomogeneous Neumann boundary conditions for the activator in the singularly perturbed one-dimensional Gierer-Meinhardt reaction-diffusion system. We show that these boundary conditions necessitate the formation of spikes that concentrate in a boundary layer near the domain boundaries. Using the method of matched asymptotic expansions we construct boundary layer spikes and derive a new class of shifted Nonlocal Eigenvalue Problems for which we rigorously prove partial stability results. Moreover by using a combination of asymptotic, rigorous, and numerical methods we investigate the structure and linear stability of selected one-and two-spike patterns. In particular we find that inhomogeneous Neumann boundary conditions increase both the range of parameter values over which asymmetric two-spike patterns exist and are stable.

Bioresource technology, Jan 12, 2017

This paper studies the application of calcium oxide (CaO), peracetic acid (PAA) and a combination... more This paper studies the application of calcium oxide (CaO), peracetic acid (PAA) and a combination of both in order to reduce lignin content and increase biogas potential of cow manure and maize straw. Changes in organic matter were mainly affected by the type of reagent use and the dosage, with minimum influence of exposure time and dilution. Changes in pH may limit the application of chemicals. Increase in biogas production with a combination of CaO and PAA, and separate application of PAA and CaO was 156.5%, 39.1% and 26.1% for cow manure and 125%, 137.5% and 37.5% for maize straw, respectively, compared to unpretreated samples. Pretreating cow manure with the aforementioned reagents does not increase the profitability of a biogas plant due mainly to the increase in operational costs from the intensive use of chemicals.

American Journal of Obstetrics and Gynecology, 2016

OBJECTIVE: To evaluate whether an increased duration of the second stage of labor in a primiparou... more OBJECTIVE: To evaluate whether an increased duration of the second stage of labor in a primiparous singleton term delivery increases the risk of preterm birth in the subsequent singleton pregnancy. METHODS: Cohort study of retrospectively collected obstetric data at Lehigh Valley Health Network between April 2007 and November 2013. The characteristics of a woman's first pregnancy delivered ≥ 37 weeks gestation were obtained and the length of the second stage of labor was used as the exposure of interest. Characteristics of the woman's subsequent delivered pregnancy were analyzed and the gestational age at delivery was the primary outcome of interest. Other outcomes of interest included the diagnosis of spontaneous preterm labor and/ or the diagnosis of cervical shortening in the second pregnancy. RESULTS: Twenty-six out of thirty-three patients were identified as eligible for inclusion in the study, for a total of 52 pregnancies included in analysis. Out of the pregnancies analyzed, 3 patients delivered preterm in their second pregnancy. Our primary outcome of interest, gestational age in a subsequent pregnancy, was similar between the groups (38.8 weeks + 1.5 weeks in those with a normal second stage of labor (n=17, 73.9%) vs. 39.6 + 1.0 weeks in those with a prolonged second stage of labor (n=6, 26.1%), p=0.26). CONCLUSION: Our data thus far does not demonstrate a difference in gestational age among women by the length of the second stage of labor, although results are limited by the small sample size. Through this study possible risk factors for cervical shortening and spontaneous preterm birth in women who have previously delivered at term will be evaluated. The observations made from this study may influence health care providers to make recommendations for preterm delivery screening and labor management in women who do not have obvious risk factors for preterm birth.

Este artículo expone una metodología desarrollada por los autores para estimular la creación sono... more Este artículo expone una metodología desarrollada por los autores para estimular la creación sonora y musical en estudiantes de Diseño. Se exponen los diversos fundamentos teóricos que dan pie a esta práctica, además de los lineamientos específicos para su desarrollo. Basados en valoraciones cualitativas de la producción musical de los estudiantes y en el impacto en la cognición acústica manifiesto por ellos, se concluye la efectividad de su práctica.

Theory and Decision, 2004

We reconsider the Myerson value and the position value for communication situations. In case the ... more We reconsider the Myerson value and the position value for communication situations. In case the underlying game is a unanimity game, we show that each of these values can be computed using the inclusionexclusion principle. Linearity of both values permits us to calculate them without needing the dividends of the induced games (graph-restricted game and link game). The expression of these dividends is only derived in the existing literature for special communication situations. Moreover, the associated inclusion-exclusion decomposability property depends on what we have called the graph allocation rule. This rule is the relative degree (relative indicator) for the position value (Myerson value).

Microbiology, 1999

Human enterotoxigenic Escherichia coli (ETEC) produces a type IV pilus termed tongus which is enc... more Human enterotoxigenic Escherichia coli (ETEC) produces a type IV pilus termed tongus which is encoded on large plasmids in association with colonization factor antigens (CFAs) and enterotoxins. A plasmid-derived 7 kbp BamHl DNA fragment hybridizing with an oligonucleotide probe designed from the aminoterminal amino acid sequence of the denatured 22 kDa structural longus pilin subunit was subcloned and sequenced. DNA sequencing analysis revealed an open reading frame, designated lngA, whose predicted amino acid sequence matched perfectly the N-terminal sequence of LngA obtained by Edman degradation. h g A is the first gene described of the longus gene cluster. Cloned h g A encoded and expressed a prepilin protein of 236 residues with a calculated mass of 25-17 kDa. The prepilin is apparently processed into a mature pilin of 206 residues with a calculated mass of 21.5 kDa. The predicted peptide sequence of lngA showed 7 8 8 and 37% identity to CFAllll pilin (CofA) of ETEC and the toxin-coregulated pilus (TcpA) of Vibrio cholerae. Peptide sequence homology between lngA and cofA was more prominent towards the amino terminus than within the carboxy region. Like other type IV pilins, LngA contains two cysteine residues towards the carboxy-terminal region. Transmission electron microscopy and immunoblot analysis of ETEC strains expressing either longus or CFNIIi detected antigenic differences between native and denatured epitopes of these pili. In addition, differential regulation of pilus expression was identified when ETEC strains were grown in different media. Our data indicate that longus and CFAllll are two distinct but yet highly related type IV pili of ETEC.

Journal of Applied Physics, 2011

Quantum dot-plasmon waveguide systems are of interest for the active control of plasmon propagati... more Quantum dot-plasmon waveguide systems are of interest for the active control of plasmon propagation, and consequently, the development of active nanophotonic devices such as nano-sized optical transistors. This paper is concerned with how varying aspect ratio of the waveguide crosssection affects the quantum dot-plasmon coupling. We compare a stripe waveguide with an equivalent nanowire, illustrating that both waveguides have a similar coupling strength to a nearby quantum dot for small waveguide cross-section, thereby indicating that stripe lithographic waveguides have strong potential use in quantum dot-plasmon waveguide systems. We also demonstrate that changing the aspect ratio of both stripe and wire waveguides can increase the spontaneous emission rate of the quantum dot into the plasmon mode, by up to a factor of five. The results of this paper will contribute to the optimisation of quantum dot-plasmon waveguide systems and help pave the way for the development of active nanophotonics devices.

International Journal of Radiation Oncology*Biology*Physics, 2002

Purpose: Intensity-modulated arc therapy (IMAT) is a method for delivering intensity-modulated ra... more Purpose: Intensity-modulated arc therapy (IMAT) is a method for delivering intensity-modulated radiation therapy (IMRT) using rotational beams. During delivery, the field shape, formed by a multileaf collimator (MLC), changes constantly. The objectives of this study were to (1) clinically implement the IMAT technique, and (2) evaluate the dosimetry in comparison with conventional three-dimensional (3D) conformal techniques. Methods and Materials: Forward planning with a commercial system (RenderPlan 3D, Precision Therapy International, Inc., Norcross, GA) was used for IMAT planning. Arcs were approximated as multiple shaped fields spaced every 5-10°around the patient. The number and ranges of the arcs were chosen manually. Multiple coplanar, superimposing arcs or noncoplanar arcs with or without a wedge were allowed. For comparison, conventional 3D conformal treatment plans were generated with the same commercial forward planning system as for IMAT. Intensity-modulated treatment plans were also created with a commercial inverse planning system (CORVUS, Nomos Corporation). A leaf-sequencing program was developed to generate the dynamic MLC prescriptions. IMAT treatment delivery was accomplished by programming the linear accelerator (linac) to deliver an arc and the MLC to step through a sequence of fields. Both gantry rotation and leaf motion were enslaved to the delivered MUs. Dosimetric accuracy of the entire process was verified with phantoms before IMAT was used clinically. For each IMAT treatment, a dry run was performed to assess the geometric and dosimetric accuracy. Both the central axis dose and dose distributions were measured and compared with predictions by the planning system. Results: By the end of May 2001, 50 patients had completed their treatments with the IMAT technique. Two to five arcs were needed to achieve highly conformal dose distributions. The IMAT plans provided better dose uniformity in the target and lower doses to normal structures than 3D conformal plans. The results varied when the comparison was made with fixed gantry IMRT. In general, IMAT plans provided more uniform dose distributions in the target, whereas the inverse-planned fixed gantry treatments had greater flexibility in controlling dose to the critical structures. Because the field sizes and shapes used in the IMAT were similar to those used in conventional treatments, the dosimetric uncertainty was very small. Of the first 32 patients treated, the average difference between the measured and predicted doses was ؊0.54 ؎ 1.72% at isocenter. The 80%-95% isodose contours measured with film dosimetry matched those predicted by the planning system to within 2 mm. The planning time for IMAT was slightly longer than for generating conventional 3D conformal plans. However, because of the need to create phantom plans for the dry run, the overall planning time was doubled. The average time a patient spent on the table for IMAT treatment was similar to conventional treatments. Conclusion: Initial results demonstrated the feasibility and accuracy of IMAT for achieving highly conformal dose distributions for different sites. If treatment plans can be optimized for IMAT cone beam delivery, we expect IMAT to achieve dose distributions that rival both slice-based and fixed-field IMRT techniques. The efficient delivery with existing linac and MLC makes IMAT a practical choice.

Cancer Research, 2007

Balanced expression of proteases and their inhibitors is one prerequisite of tissue homeostasis. ... more Balanced expression of proteases and their inhibitors is one prerequisite of tissue homeostasis. Metastatic spread of tumor cells through the organism depends on proteolytic activity and is the death determinant for cancer patients. Paradoxically, increased expression of tissue inhibitor of metalloproteinases-1 (TIMP-1), a natural inhibitor of several endometalloproteinases, including matrix metalloproteinases and a disintegrin and metalloproteinase-10 (ADAM-10), in cancer patients is negatively correlated with their survival, although TIMP-1 itself inhibits invasion of some tumor cells. Here, we show that elevated stromal expression of TIMP-1 promotes liver metastasis in two independent tumor models by inducing the hepatocyte growth factor (HGF) signaling pathway and expression of several metastasis-associated genes, including HGF and HGF-activating proteases, in the liver. We also found in an in vitro assay that suppression of ADAM-10 is in principle able to prevent shedding of cMet, which may be one explanation for the increase of cell-associated HGF receptor cMet in livers with elevated TIMP-1. Similar TIMP-1-associated changes in gene expression were detected in livers of patients with metastatic colorectal cancer. The newly identified role of TIMP-1 to create a prometastatic niche may also explain the TIMP-1 paradoxon.

$Research paper thumbnail of Histopathologic characterization of radioactive iodine‐refractory fluorodeoxyglucose‐positron emission tomography‐positive thyroid carcinoma$

Cancer, 2008

BACKGROUND. Radioactive iodine-refractory (RAIR) 18F-fluorodeoxyglucose (FDG)-positron emission t... more BACKGROUND. Radioactive iodine-refractory (RAIR) 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) positive thyroid carcinomas represent the major cause of deaths from thyroid carcinomas (TC) and are therefore the main focus of novel target therapies. However, to the authors' knowledge, the histology of FDG-PET-positive RAIR metastatic thyroid carcinoma has not been described to date. METHODS. Metastatic tissue from RAIR PET-positive patients identified between 1996 and 2003 at the study institution were selected for histologic examination. The biopsied metastatic site corresponded to a FDG-PET positive lesion sampled within 2 years (87% of which were sampled within 1 year) of the PET scan. Detailed microscopic examination was performed on the metastatic deposit and the available primary tumors. Poorly differentiated thyroid carcinomas (PDTC) were defined on the basis of high mitotic activity (5 mitoses/10 high-power fields) and/or tumor necrosis. Other types of carcinomas were defined by conventional criteria. The histology of the metastases and primary were analyzed, with disease-specific survival (DSS) as the endpoint. RESULTS. A total of 70 patients satisfied the selection criteria, 43 of whom had primary tumors available for review. Histologic characterization of the metastasis/recurrence in 70 patients revealed that 47.1% (n 5 33 patients) had PDTC, 20% (n 5 14 patients) had the tall cell variant (TCV) of papillary thyroid carcinoma, 22.9% (n 5 16 patients) had well-differentiated papillary thyroid carcinoma (WDPTC), 8.6% (n 5 6 patients) had Hurthle cell carcinoma (HCC), and 1.4% (n 5 1 patient) had anaplastic carcinomas. The histopathologic distribution of the tumor in the primaries was: PDTC, 51%; TCV, 19%; WDPTC, 23%; and widely invasive HCC, 7%. A differing histology between the primary tumor and metastasis was observed in 37% of cases (n 5 16 patients). In the majority of instances (63%; 10 of 16 patients) this was noted as transformation to a higher grade. Of the primary tumors classified as PTC, 70% progressed to more aggressive histotypes in the metastasis. Tumor necrosis and extensive extrathyroid extension in the primary tumor were found to be independent predictors of poorer DSS in this group of patients (P 5 .015). Approximately 68% of the PDTC primary tumors were initially classified by the primary pathologist as better-differentiated tumors on the basis of the presence of papillary and/or follicular architecture or the presence of typical PTC nuclear features. CONCLUSIONS. Several observations can be made based on the results of the current study. The majority of metastases in patients with RAIR PET-positive metastases are of a histologically aggressive subtype. However, well-differentiated RAIR metastatic disease is observable. Poorly differentiated disease is underrecognized in many cases if defined by architectural and nuclear features alone. The presence of tumor necrosis was found to be a strong predictor of aggressive behavior, even within this group of clinically aggressive tumors. Finally, there is a

Acta Societatis Botanicorum Poloniae, 2011

The intra- and interpopulational geographic variation of three distant populations of J... more The intra- and interpopulational geographic variation of three distant populations of J. oxycedrus subsp. macrocarpa was examined biometrically on the basis of morphological key-characters of needles, seeds and cones. The shortest Euclidean distances were used in the agglomerative grouping of closest neighbourhood and discrimination analysis with principal component analysis (PCA) was performed to verify the south-north differentiation of the taxon in Italy. Most of the cone and seed dimensional characters are correlated. No significant correlations were found between cone and needle characters. The sampled populations differ only insignificantly from one another, while the intrapopulational variation is slightly higher. Cone length as well as seed number, width and thickness were significantly correlated with geographic latitude, while the other four characters are not. Differences in cone shape were observed between individuals, so that se...

Journal of Thoracic Oncology, 2010

Radiation therapy often plays a critical role in the treatment of thymic malignancies. However, b... more Radiation therapy often plays a critical role in the treatment of thymic malignancies. However, because of the location of these tumors, historically patients have been at a significant risk for radiationrelated toxicity such as pericardial effusions, radiation pneumonitis, long-term pulmonary fibrosis, and occasional long-term esophageal stricture, particularly for unresectable thymoma. Recent advancements in technology have provided the treating radiation oncologist with the ability to more accurately target the region at risk while sparing normal structures. In this review, we provide an overview of key advances in radiation techniques for thymoma over the past two decades. These techniques include 3D conformal therapy, intensity-modulated radiation therapy, 4D treatment planning, adaptive radiation therapy, and proton therapy. Each advancement has brought with it unique advantages in maintaining long-term disease control while improving quality of life in this manageable disease.