Errol Sam

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Steven Pinker

Harvard University

Edith Szanto

University of Alabama - Tuscaloosa

Martin van Bruinessen

Universiteit Utrecht

John Johnson

Pennsylvania State University

Armando Marques-Guedes

UNL - New University of Lisbon

Marc Goergen

IE BUSINESS SCHOOL

Thomas L Webb

The University of Sheffield

Joas Wagemakers

Utrecht University

Vusat Azizov

Azerbaijan State University of Economics (UNEC)

Petra Sijpesteijn

Leiden University

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Papers by Errol Sam

Observation of unusual structure in the low-temperature conductance of carbon nanotubes

Carbon nanotubes grown by chemical vapor deposition on a oxidized silicon substrate were contacte... more Carbon nanotubes grown by chemical vapor deposition on a oxidized silicon substrate were contacted to form a gated sample consisting of a pair of tubes in parallel. The sample was tested at low temperature and high magnetic field using a dilution refrigerator and superconducting magnet. The current versus bias voltage graph shows a general trend consistent with the linear relationship except at low voltage. Further investigation is done by computing the differential conductance (dI/dV) and investigating how it varies with bias voltage. Here we see some intriguing behavior including a substantial increase in conductivity near zero voltage and a pronounced asymmetry with bias voltage. The temperature dependence of the zero field peak and asymmetry show that they appear at low temperatures and receding quickly by 3.0K. However, the magnetic field dependence is less intuitive. There are apparent shifts and possible splits that seem to develop but they are not followed in a manner consistent with simple theory.

Whole-Genome Comparison of Two Campylobacter jejuni Isolates of the Same Sequence Type Reveals Multiple Loci of Different Ancestral Lineage

PLOS One, 2011

Campylobacter jejuni ST-474 is the most important human enteric pathogen in New Zealand, and yet ... more Campylobacter jejuni ST-474 is the most important human enteric pathogen in New Zealand, and yet this genotype is rarely found elsewhere in the world. Insight into the evolution of this organism was gained by a whole genome comparison of two ST-474, flaA SVR-14 isolates and other available C. jejuni isolates and genomes. The two isolates were collected from different sources, human (H22082) and retail poultry (P110b), at the same time and from the same geographical location. Solexa sequencing of each isolate resulted in *1.659 Mb (H22082) and *1.656 Mb (P110b) of assembled sequences within 28 (H22082) and 29 (P110b) contigs. We analysed 1502 genes for which we had sequences within both ST-474 isolates and within at least one of 11 C. jejuni reference genomes. Although 94.5% of genes were identical between the two ST-474 isolates, we identified 83 genes that differed by at least one nucleotide, including 55 genes with non-synonymous substitutions. These covered 101 kb and contained 672 point differences. We inferred that 22 (3.3%) of these differences were due to mutation and 650 (96.7%) were imported via recombination. Our analysis estimated 38 recombinant breakpoints within these 83 genes, which correspond to recombination events affecting at least 19 loci regions and gives a tract length estimate of *2 kb. This includes a *12 kb region displaying non-homologous recombination in one of the ST-474 genomes, with the insertion of two genes, including ykgC, a putative oxidoreductase, and a conserved hypothetical protein of unknown function. Furthermore, our analysis indicates that the source of this recombined DNA is more likely to have come from C. jejuni strains that are more closely related to ST-474. This suggests that the rates of recombination and mutation are similar in order of magnitude, but that recombination has been much more important for generating divergence between the two ST-474 isolates.

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Lentiviral Vector-Transduced Dendritic Cells Induce Specific T Cell Response in a Nonhuman Primate Model

Human Gene Therapy, 2005

Dendritic cells (DCs) are effective in stimulating and controlling the outcome of T cell response... more Dendritic cells (DCs) are effective in stimulating and controlling the outcome of T cell responses. Human immunodeficiency virus type 1-based lentiviral vectors can achieve sustained transduction of genes/antigens in dividing and nondividing cells, thus representing a candidate vector for stable expression of antigens in DCs. We previously established conditions for transduction of purified cytokine mobilized rhesus CD34(+) cells in vitro, and transplantation of the autologous transduced cells in a nonhuman primate model in vivo. In the present study, we transplanted DCs derived from EGFP-transduced CD34(+) cells into nonmyeloablated rhesus macaques. Transplantation of DCs stably expressing EGFP into autologous animals induces persistent, long-lived (up to 100 weeks) EGFP-specific T cell responses. Of note, no humoral responses against EGFP are detected in the transplanted animals. These studies provide, to our knowledge, the first demonstration that lentiviral transduction of CD34(+) progenitor cells subsequently differentiated to DCs is capable of priming a specific T cell response in a nonhuman primate in vivo. Taken together, our data provide formal in vivo evidence that lentivirus-transduced dendritic cells represent a potential approach in eliciting cellular immune responses in primates.

The Actn3 R577x Polymorphism In Elite Jamaican And USA Sprinters: 1067

Medicine and Science in Sports and Exercise, 2009

Analysis of unusual splitting of Kondo peak in the differential conductance of a carbon nanotube quantum dot

Carbon nanotubes grown by chemical vapor deposition on an oxidized silicon substrate were contact... more Carbon nanotubes grown by chemical vapor deposition on an oxidized silicon substrate were contacted to form a gated sample of parallel tubes. Testing was done at low temperature and high magnetic field using a dilution refrigerator and superconducting magnet. The current versus voltage graph shows asymmetry with respect to zero volts. The differential conductance (dI/dV) is computed and yields some intriguing behavior. The previous asymmetry is more apparent as is a sharp increase in conductivity near zero voltage. Temperature data further suggests a conductance peak at near zero voltage consistent with the Kondo effect. High magnetic fields, 0 to 11 Tesla in 0.5 Tesla increments, are used to probe the conductance behavior. The magnetic field tests yield unusual shapes and splitting at two critical fields.

Analysis of corrosion and oxidation on metals by spectroscopic means

Fresenius Journal of Analytical Chemistry, 1986

Diese Arbeit betont drei Gesichtspunkte oberflächenanalytischer Untersuchung, die für die Charakt... more Diese Arbeit betont drei Gesichtspunkte oberflächenanalytischer Untersuchung, die für die Charakterisierung von Korrosionsmechanismen als besonders wesentlich erachtet werden: die chemische Bindung, die mikroskopische Analyse und die verbesserte Steuerung experimenteller Bedingungen. Die Röntgen-Photoelektronenspektroskopie (XPS oder ESCA) ist für die Unterscheidung chemischer Spezies besonders erfolgreich gewesen. Die Anwendung von XPS beschränkt sich jedoch im wesentlichen auf die äußere Oberfläche einer Schicht. Die Aufnahme von Tiefenprofilen mit Hilfe von Ionenbeschuß vermindert häufig die chemische Information, die vom Schichtinnern und vom Metall-Oxid-Interface erhältlich wäre; und hier spielen sich oft die Korrosionsvorgänge ab. Mechanische Methoden des Dünnschichtabtrags sind somit aufgefordert, XPS bis an die Leistungsgrenze zu bringen. Mikroskopische Untersuchungen von Korrosionsschichten mittels Raster-Auger-Mikroskopie (SAM) oder Sekundärionen-Massenspektrometrie können Effekte wie die Korngrenzensegregation und die Oxidbildung aufdecken. Ein weiterer bedeutender Gesichtspunkt der Analyse von Korrosionsschichten ist die Behandlung der Metalloberflächen selbst. Die oxidierte Oberfläche kann durch Behandlungsfehler wie z.B. Kaltbearbeitung oder Verunreinigung stark beeinflußt werden. An Hand von drei verschiedenen Beispielen werden diese Aspekte illustriert: (i) die Analyse einer Molybdän-Schutzschicht auf Stahl; (ii) die Untersuchung von Korrosionsprodukten auf 304-Edelstahl; und (iii) die Effekte des H+-Ionenbeschusses zum Ausheilen mechanischer Schäden auf der Oberfläche von Ni-CrLegierungen, vor der Oxidation. This paper addresses three aspects of the surface analytical experiment which are felt to be particularly crucial in characterizing corrosion mechanisms: chemical speciation, microscopic analysis and improved control of experimental conditions. X-ray Photoelectron Spectroscopy (XPS or ESCA) has been particularly effective in differentiating chemical species. The major chemical use of XPS is limited however to the outer surface of the film. Depth profiling by ion bombardment frequently degrades the chemical information available in the film interior and at the metal-oxide interface, and this is often where corrosion mechanisms are established. Mechanical methods of film penetration are thus encouraged to use XPS to its maximum capability. Microscopic analysis of corrosion surfaces using Scanning Auger Microscopy (SAM) or Secondary Ion Mass Spectrometry can reveal effects such as grain boundary segregation and oxide nucleation. Another important aspect of corrosion film analysis is the preparation of the metal surface itself. The oxidized surface can be strongly influenced by preparation artefacts such as cold work or impurities. Three different studies are used to illustrate these aspects: (i) the analysis of a molybdenum inhibitor layer on a steel surface; (ii) the study of corrosion product release from 304-stainless steel; and (iii) the effects of H+ ion bombardment to anneal mechanical work on Ni-Cr alloy surfaces, prior to oxidation.

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The 2010 Interim Report of the Long-Baseline Neutrino Experiment Collaboration Physics Working Groups

In early 2010, the Long-Baseline Neutrino Experiment (LBNE) science collaboration initiated a stu... more In early 2010, the Long-Baseline Neutrino Experiment (LBNE) science collaboration initiated a study to investigate the physics potential of the experiment with a broad set of different beam, near- and far-detector configurations. Nine initial topics were identified as scientific areas that motivate construction of a long-baseline neutrino experiment with a very large far detector. We summarize the scientific justification for each topic and the estimated performance for a set of far detector reference configurations. We report also on a study of optimized beam parameters and the physics capability of proposed Near Detector configurations. This document was presented to the collaboration in fall 2010 and updated with minor modifications in early 2011.

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Induction of Transgene-Specific Immunological Tolerance in Myeloablated Nonhuman Primates Using Lentivirally Transduced CD34+ Progenitor Cells

Molecular Therapy, 2003

Modeling human hematopoietic progenitor cell gene therapy in nonhuman primates allows long-term e... more Modeling human hematopoietic progenitor cell gene therapy in nonhuman primates allows long-term evaluation of safety, maintenance of gene expression, and potential immune response against transgene products. We transplanted autologous G-CSF/SCF-mobilized CD34+ cells transduced with lentiviral vectors expressing EGFP into myeloablated rhesus macaques. To date, more than 4 years posttransplantation, 0.5-8% EGFP expression is maintained in multiple cell lineages. The animals remain healthy with no evidence of hematopoietic abnormalities or malignancies. To assess immune functions, we actively immunized two of our transplanted animals with purified rEGFP proteins and CpG adjuvant and demonstrated stable levels of EGFP+ cell populations maintained for over 29 months despite four active immunizations. We did not detect a persistent anti-EGFP antibody response or anti-EGFP T cell response in these immunized animals. Immune response to an irrelevant antigen was normal. Taken together, our data provide formal support that transplantation of lentivirally transduced CD34+ progenitor cells in myeloablated rhesus macaques induces specific immunological tolerance toward a foreign transgene.

The 3rd Japan–US DNA Repair Meeting, Sendai, Japan, May 7–11, 2007

Dna Repair, 2007

d n a r e p a i r 6 ( 2 0 0 7 ) 1545-1555 a v a i l a b l e a t w w w . s c i e n c e d i r e c t... more

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Angiotensin-i Converting Enzyme Polymorphism In Elite Jamaican And USA Sprinters: 1068

Medicine and Science in Sports and Exercise, 2009

The maternal inheritance of mitochondrial DNA (mtDNA) has enabled construction of detailed phylog... more The maternal inheritance of mitochondrial DNA (mtDNA) has enabled construction of detailed phylogenies. Analysis of key polymorphisms from these phylogenies allows mtDNA to be assigned to haplogroups, which have been associated with elite endurance performance. Purpose: To compare the frequencies of mtDNA haplogroups found in elite Kenyan athletes with those in the general Kenyan population. Methods: DNA samples were obtained from 221 national level Kenyan athletes (N), 70 international Kenyan athletes (I), and 85 members of the general Kenyan population (C). mtDNA haplogroups were classified by sequencing 340 bases of hypervariable section (HVS I) and by genotyping known restriction sites. Frequency differences between groups were assessed using exact tests of population differentiation. Results: The haplogroup distribution of national (P = 0.023) and international athletes (P G 0.001) differed significantly from controls, with international athletes showing a greater proportion of L0 haplogroups (C = 15%, N = 18%, I = 30%) and lower proportion of L3* haplogroups (C = 48%, N = 36%, I = 26%). Although a high number of international athletes originated from the Rift Valley province relative to controls (C = 20%, N = 65%, I = 81%), subjects from this province did not differ in haplogroup distribution from other regions (P = 0.23). Nor did Bantu subjects differ from Nilotic (P = 0.12) despite an overrepresentation of Nilotic languages among the athletes. Conclusions: International athletes differed in their mtDNA haplogroup distribution relative to the general Kenyan population. They displayed an excess of L0 haplogroups and a dearth of L3* haplogroups. These findings suggest that mtDNA haplogroups are influential in elite Kenyan distance running, although population stratification cannot be ruled out.

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