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Papers by Andres Felipe Jimenez Lopez

Nature, 2012

There is intense debate about whether all Native Americans stem from one migration or multiple wa... more There is intense debate about whether all Native Americans stem from one migration or multiple waves of migration from Asia. In addition, little is known about the principal settlement routes and patterns of population diversification within the Americas. We assembled a dataset of 55 Native American and 19 Siberian populations typed at over 370,000 polymorphisms, the most comprehensive survey of genetic diversity in Native Americans to date, and masked out segments of recent European or African ancestry. Along with providing genetic support for controversial linguistic evidence for three episodes of migration from Asia, the data provide strong evidence for a southward population expansion (facilitated by the coast) with sequential splits and little gene flow after divergence. An important exception to this pattern is the history of Chibchanspeakers around the Panama isthmus, who our data suggest derive from a >5,000 year old mixture of South American and North American lineages, highlighting the isthmus as a region of genetic interaction between both hemispheres. Our results refute recent interpretations of mitochondrial DNA (mtDNA) positing a single settlement wave. They also highlight how genome-wide analyses of data directly accounting for the confounder of non-Native admixture can be used to document previously unknown historical events.

Journal of clinical …, 2005

To compare the antitumor activity and toxicity of the two induction chemotherapy treatments of pa... more To compare the antitumor activity and toxicity of the two induction chemotherapy treatments of paclitaxel, cisplatin, and fluorouracil (FU; PCF) versus standard cisplatin and FU (CF), both followed by chemoradiotherapy (CRT), in locally advanced head and neck cancer (HNC). Eligibility criteria included biopsy-proven, previously untreated, stage III or IV locally advanced HNC. Patients received either CF (cisplatin 100 mg/m2 on day 1 plus FU 1000 [corrected] mg/m2 continuous infusion on days 1 through 5) or PCF (paclitaxel 175 mg/m2 on day 1, cisplatin 100 mg/m2 on day 2, and FU 500 mg/m2 continuous infusion on days 2 through 6); both regimens were administered for three cycles every 21 days. Patients with complete response (CR) or partial response of greater than 80% in primary tumor received additional CRT (cisplatin 100 mg/m2 on days 1, 22, and 43 plus 70 Gy). A total of 382 eligible patients were randomly assigned to CF (n = 193) or PCF (n = 189). The CR rate was 14% in the CF arm v 33% in the PCF arm (P < .001). Median time to treatment failure was 12 months in the CF arm compared with 20 months in the PCF arm (log-rank test, P = .006; Tarone-Ware, P = .003). PCF patients had a trend to longer overall survival (OS; 37 months in CF arm v 43 months in PCF arm; log-rank test, P = .06; Tarone-Ware, P = .03). This difference was more evident in patients with unresectable disease (OS: 26 months in CF arm v 36 months in PCF arm; log-rank test, P = .04; Tarone-Ware, P = .03). CF patients had a higher occurrence of grade 2 to 4 mucositis than PCF patients (53% v 16%, respectively; P < .001). Induction chemotherapy with PCF was better tolerated and resulted in a higher CR rate than CF. However, new trials that compare induction chemotherapy plus CRT versus CRT alone are needed to better define the role of neoadjuvant treatment.

Archivos de …, 2008

Spontaneous pneumothorax, or the presence of air in the pleural space not caused by injury or med... more Spontaneous pneumothorax, or the presence of air in the pleural space not caused by injury or medical intervention, is a significant clinical problem. We propose a method for classifying cases into 3 categories: partial, complete, and complete with total lung collapse. This classification, together with a clinical assessment, would provide sufficient information to enable physicians to decide on an approach to treatment. This update introduces simple aspiration in an outpatient setting as a treatment option that has yielded results comparable to conventional drainage in the management of uncomplicated primary spontaneous pneumothorax; this technique is not, as yet, widely used in Spain.

… of Chromatography B, 2003

Dexamethasone, as some other synthetic corticosteroids, is licensed for therapy in veterinary pra... more Dexamethasone, as some other synthetic corticosteroids, is licensed for therapy in veterinary practice, but its misuse as a growth promotor, often in combination with beta-agonists, is forbidden. In this report an analytical method is described for the detection and confirmation of very low concentrations of dexamethasone in urine. The influence of enzymatic hydrolysis time of samples with glucuronidase was studied. The proposed method consisted of the enzymatic hydrolysis of urine samples, which were then extracted and concentrated using solid-phase cartridges with mixed reversed-phase materials (OASIS). No further clean-up step was found to be necessary. Eluates were derivatized following a previously described method [Analyst 119 (1994) 2557]. Detection, identification and quantification of residues of this compound was carried out by gas chromatography with mass spectrometry in the negative chemical ionization mode. The proposed procedure permits the determination of dexamethasone in urine at levels as low as 0.2 ng ml(-1)

The Journal of …, 1996

1,3-Dipolar cycloaddition of 1,3-thiazolium-4-olates, readily prepared from thioureido derivative... more 1,3-Dipolar cycloaddition of 1,3-thiazolium-4-olates, readily prepared from thioureido derivatives, and trans-beta-nitrostyrene at room temperature in methylene chloride (48 h) resulted in two readily separable diastereomeric racemic 4,5-dihydrothiophenes via transient cycloadducts that underwent rearrangement under these reaction conditions. Using chiral carbohydrate-derived nitroalkenes, two diastereomeric dihydrothiophenes were obtained, showing that regiospecificity and facial selectivity were involved in these cycloadditions. (1)H NMR data and trapping experiments with isolated initial cycloadducts indicated that the cycloadditions were reversible and accounted for observed adduct and final product ratios. Single-crystal X-ray determinations established the structures of critical intermediates and products, and PM3 semiempirical MO calculations provide a rationalization for both the reactivity of the thiazolium-4-olates and the regioselectivity observed in the cycloadditions.

Physics Letters B, 2012

This Letter presents evidence for the associated production of a W boson and a top quark using 2.... more This Letter presents evidence for the associated production of a W boson and a top quark using 2.05 fb −1 of pp collision data at √ s = 7 TeV accumulated with the ATLAS detector at the LHC. The analysis is based on the selection of the dileptonic final states with events featuring two isolated leptons, electron or muon, with significant transverse missing momentum and at least one jet. An approach based on boosted decision trees has been developed to improve the discrimination of single top-quark Wt events from background. A template fit to the final classifier distributions is performed to determine the cross-section. The result is incompatible with the background-only hypothesis at the 3.3σ level, the expected sensitivity assuming the Standard Model production rate being 3.4σ. The corresponding cross-section is determined and found to be σ Wt = 16.8 ± 2.9 (stat) ± 4.9 (syst) pb, in good agreement with the Standard Model expectation. From this result the CKM matrix element |V tb | = 1.03 +0.16 −0.19 is derived assuming that the Wt production through |V ts | and |V td | is small.

Nature, 2012

There is intense debate about whether all Native Americans stem from one migration or multiple wa... more There is intense debate about whether all Native Americans stem from one migration or multiple waves of migration from Asia. In addition, little is known about the principal settlement routes and patterns of population diversification within the Americas. We assembled a dataset of 55 Native American and 19 Siberian populations typed at over 370,000 polymorphisms, the most comprehensive survey of genetic diversity in Native Americans to date, and masked out segments of recent European or African ancestry. Along with providing genetic support for controversial linguistic evidence for three episodes of migration from Asia, the data provide strong evidence for a southward population expansion (facilitated by the coast) with sequential splits and little gene flow after divergence. An important exception to this pattern is the history of Chibchanspeakers around the Panama isthmus, who our data suggest derive from a >5,000 year old mixture of South American and North American lineages, highlighting the isthmus as a region of genetic interaction between both hemispheres. Our results refute recent interpretations of mitochondrial DNA (mtDNA) positing a single settlement wave. They also highlight how genome-wide analyses of data directly accounting for the confounder of non-Native admixture can be used to document previously unknown historical events.

Journal of clinical …, 2005

To compare the antitumor activity and toxicity of the two induction chemotherapy treatments of pa... more To compare the antitumor activity and toxicity of the two induction chemotherapy treatments of paclitaxel, cisplatin, and fluorouracil (FU; PCF) versus standard cisplatin and FU (CF), both followed by chemoradiotherapy (CRT), in locally advanced head and neck cancer (HNC). Eligibility criteria included biopsy-proven, previously untreated, stage III or IV locally advanced HNC. Patients received either CF (cisplatin 100 mg/m2 on day 1 plus FU 1000 [corrected] mg/m2 continuous infusion on days 1 through 5) or PCF (paclitaxel 175 mg/m2 on day 1, cisplatin 100 mg/m2 on day 2, and FU 500 mg/m2 continuous infusion on days 2 through 6); both regimens were administered for three cycles every 21 days. Patients with complete response (CR) or partial response of greater than 80% in primary tumor received additional CRT (cisplatin 100 mg/m2 on days 1, 22, and 43 plus 70 Gy). A total of 382 eligible patients were randomly assigned to CF (n = 193) or PCF (n = 189). The CR rate was 14% in the CF arm v 33% in the PCF arm (P < .001). Median time to treatment failure was 12 months in the CF arm compared with 20 months in the PCF arm (log-rank test, P = .006; Tarone-Ware, P = .003). PCF patients had a trend to longer overall survival (OS; 37 months in CF arm v 43 months in PCF arm; log-rank test, P = .06; Tarone-Ware, P = .03). This difference was more evident in patients with unresectable disease (OS: 26 months in CF arm v 36 months in PCF arm; log-rank test, P = .04; Tarone-Ware, P = .03). CF patients had a higher occurrence of grade 2 to 4 mucositis than PCF patients (53% v 16%, respectively; P < .001). Induction chemotherapy with PCF was better tolerated and resulted in a higher CR rate than CF. However, new trials that compare induction chemotherapy plus CRT versus CRT alone are needed to better define the role of neoadjuvant treatment.

Archivos de …, 2008

Spontaneous pneumothorax, or the presence of air in the pleural space not caused by injury or med... more Spontaneous pneumothorax, or the presence of air in the pleural space not caused by injury or medical intervention, is a significant clinical problem. We propose a method for classifying cases into 3 categories: partial, complete, and complete with total lung collapse. This classification, together with a clinical assessment, would provide sufficient information to enable physicians to decide on an approach to treatment. This update introduces simple aspiration in an outpatient setting as a treatment option that has yielded results comparable to conventional drainage in the management of uncomplicated primary spontaneous pneumothorax; this technique is not, as yet, widely used in Spain.

… of Chromatography B, 2003

Dexamethasone, as some other synthetic corticosteroids, is licensed for therapy in veterinary pra... more Dexamethasone, as some other synthetic corticosteroids, is licensed for therapy in veterinary practice, but its misuse as a growth promotor, often in combination with beta-agonists, is forbidden. In this report an analytical method is described for the detection and confirmation of very low concentrations of dexamethasone in urine. The influence of enzymatic hydrolysis time of samples with glucuronidase was studied. The proposed method consisted of the enzymatic hydrolysis of urine samples, which were then extracted and concentrated using solid-phase cartridges with mixed reversed-phase materials (OASIS). No further clean-up step was found to be necessary. Eluates were derivatized following a previously described method [Analyst 119 (1994) 2557]. Detection, identification and quantification of residues of this compound was carried out by gas chromatography with mass spectrometry in the negative chemical ionization mode. The proposed procedure permits the determination of dexamethasone in urine at levels as low as 0.2 ng ml(-1)

The Journal of …, 1996

1,3-Dipolar cycloaddition of 1,3-thiazolium-4-olates, readily prepared from thioureido derivative... more 1,3-Dipolar cycloaddition of 1,3-thiazolium-4-olates, readily prepared from thioureido derivatives, and trans-beta-nitrostyrene at room temperature in methylene chloride (48 h) resulted in two readily separable diastereomeric racemic 4,5-dihydrothiophenes via transient cycloadducts that underwent rearrangement under these reaction conditions. Using chiral carbohydrate-derived nitroalkenes, two diastereomeric dihydrothiophenes were obtained, showing that regiospecificity and facial selectivity were involved in these cycloadditions. (1)H NMR data and trapping experiments with isolated initial cycloadducts indicated that the cycloadditions were reversible and accounted for observed adduct and final product ratios. Single-crystal X-ray determinations established the structures of critical intermediates and products, and PM3 semiempirical MO calculations provide a rationalization for both the reactivity of the thiazolium-4-olates and the regioselectivity observed in the cycloadditions.

Physics Letters B, 2012

This Letter presents evidence for the associated production of a W boson and a top quark using 2.... more This Letter presents evidence for the associated production of a W boson and a top quark using 2.05 fb −1 of pp collision data at √ s = 7 TeV accumulated with the ATLAS detector at the LHC. The analysis is based on the selection of the dileptonic final states with events featuring two isolated leptons, electron or muon, with significant transverse missing momentum and at least one jet. An approach based on boosted decision trees has been developed to improve the discrimination of single top-quark Wt events from background. A template fit to the final classifier distributions is performed to determine the cross-section. The result is incompatible with the background-only hypothesis at the 3.3σ level, the expected sensitivity assuming the Standard Model production rate being 3.4σ. The corresponding cross-section is determined and found to be σ Wt = 16.8 ± 2.9 (stat) ± 4.9 (syst) pb, in good agreement with the Standard Model expectation. From this result the CKM matrix element |V tb | = 1.03 +0.16 −0.19 is derived assuming that the Wt production through |V ts | and |V td | is small.