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16,252 result(s) for "Johnson, Peter"
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Mission control : inventing the groundwork of spaceflight
\"Brave astronauts, flaring rockets, and majestic launches are only one side of the story of spaceflight. Any mission to space depends on years--if not decades--of work by thousands of dedicated individuals on the ground. These are the people whose voices offer a friendly link to Earth in the void of space, whose hands maneuver rovers across the face of planets, and whose skills guide astronauts home. This book is a long-overdue history of three major centers that have managed important missions since the dawn of the space age. In Mission Control, Michael Johnson explores the famous Johnson Space Center in Houston, the Jet Propulsion Laboratory in Pasadena, and the European Space Operations Centre in Darmstadt, Germany--each a strategically designed micro-environment responsible for the operation of spacecraft and the safety of passengers. He explains the motivations behind the location of each center and their intricate design. He shows how the robotic spaceflight missions overseen in Pasadena and Darmstadt set these centers apart from Houston, and compares the tracking networks used for different types of spacecraft. Johnson argues that the type of spacecraft and the missions they controlled--not the nations they represented--defined how the centers developed, yet these centers ended up playing vital national roles as space technology became a battleground for international power struggles in the Cold War years and even after. The most visible part of a conflict that was just as real as the wars in Korea, Vietnam, and Afghanistan and caused great global anxiety, mission control centers have served as symbols of national security in the public eye and pivotal links in the history of modern technology. Michael Peter Johnson is former director of the Skylab Oral History Project.\" --Publisher's website.
Risk prediction of covid-19 related death and hospital admission in adults after covid-19 vaccination: national prospective cohort study
AbstractObjectivesTo derive and validate risk prediction algorithms to estimate the risk of covid-19 related mortality and hospital admission in UK adults after one or two doses of covid-19 vaccination.DesignProspective, population based cohort study using the QResearch database linked to data on covid-19 vaccination, SARS-CoV-2 results, hospital admissions, systemic anticancer treatment, radiotherapy, and the national death and cancer registries.SettingsAdults aged 19-100 years with one or two doses of covid-19 vaccination between 8 December 2020 and 15 June 2021.Main outcome measuresPrimary outcome was covid-19 related death. Secondary outcome was covid-19 related hospital admission. Outcomes were assessed from 14 days after each vaccination dose. Models were fitted in the derivation cohort to derive risk equations using a range of predictor variables. Performance was evaluated in a separate validation cohort of general practices.ResultsOf 6 952 440 vaccinated patients in the derivation cohort, 5 150 310 (74.1%) had two vaccine doses. Of 2031 covid-19 deaths and 1929 covid-19 hospital admissions, 81 deaths (4.0%) and 71 admissions (3.7%) occurred 14 days or more after the second vaccine dose. The risk algorithms included age, sex, ethnic origin, deprivation, body mass index, a range of comorbidities, and SARS-CoV-2 infection rate. Incidence of covid-19 mortality increased with age and deprivation, male sex, and Indian and Pakistani ethnic origin. Cause specific hazard ratios were highest for patients with Down’s syndrome (12.7-fold increase), kidney transplantation (8.1-fold), sickle cell disease (7.7-fold), care home residency (4.1-fold), chemotherapy (4.3-fold), HIV/AIDS (3.3-fold), liver cirrhosis (3.0-fold), neurological conditions (2.6-fold), recent bone marrow transplantation or a solid organ transplantation ever (2.5-fold), dementia (2.2-fold), and Parkinson’s disease (2.2-fold). Other conditions with increased risk (ranging from 1.2-fold to 2.0-fold increases) included chronic kidney disease, blood cancer, epilepsy, chronic obstructive pulmonary disease, coronary heart disease, stroke, atrial fibrillation, heart failure, thromboembolism, peripheral vascular disease, and type 2 diabetes. A similar pattern of associations was seen for covid-19 related hospital admissions. No evidence indicated that associations differed after the second dose, although absolute risks were reduced. The risk algorithm explained 74.1% (95% confidence interval 71.1% to 77.0%) of the variation in time to covid-19 death in the validation cohort. Discrimination was high, with a D statistic of 3.46 (95% confidence interval 3.19 to 3.73) and C statistic of 92.5. Performance was similar after each vaccine dose. In the top 5% of patients with the highest predicted covid-19 mortality risk, sensitivity for identifying covid-19 deaths within 70 days was 78.7%.ConclusionThis population based risk algorithm performed well showing high levels of discrimination for identifying those patients at highest risk of covid-19 related death and hospital admission after vaccination.
Time-reversal symmetry breaking in the Fe-chalcogenide superconductors
Topological superconductivity has been sought in a variety of heterostructure systems, the interest being that a material displaying such a phenomenon could prove to be the ideal platform to support Majorana fermions, which in turn could be the basis for advanced qubit technologies. Recently, the high-Tc family of superconductors, FeTe1−xSeₓ, have been shown to exhibit the property of topological superconductivity and further, evidence has been found for the presence of Majorana fermions. We have studied the interplay of topology, magnetism, and superconductivity in the FeTe1−xSeₓ family using high-resolution laser-based photoemission. At the bulk superconducting transition, a gap opens at the chemical potential as expected. However, a second gap is observed to open at the Dirac point in the topological surface state. The associated mass acquisition in the topological state points to time-reversal symmetry breaking, probably associated with the formation of ferromagnetism in the surface layer. The presence of intrinsic ferromagnetism combined with strong spin–orbit coupling provides an ideal platform for a range of exotic topological phenomena.
Distinct genetic changes reveal evolutionary history and heterogeneous molecular grade of DLBCL with MYC/BCL2 double-hit
Using a Burkitt lymphoma-like gene expression signature, we recently defined a high-risk molecular high-grade (MHG) group mainly within germinal centre B-cell like diffuse large B-cell lymphomas (GCB-DLBCL), which was enriched for MYC/BCL2 double-hit (MYC/BCL2-DH). The genetic basis underlying MHG-DLBCL and their aggressive clinical behaviour remain unknown. We investigated 697 cases of DLBCL, particularly those with MYC/BCL2-DH (n = 62) by targeted sequencing and gene expression profiling. We showed that DLBCL with MYC/BCL2-DH, and those with BCL2 translocation, harbour the characteristic mutation signatures that are associated with follicular lymphoma and its high-grade transformation. We identified frequent MYC hotspot mutations that affect the phosphorylation site (T58) and its adjacent amino acids, which are important for MYC protein degradation. These MYC mutations were seen in a subset of cases with MYC translocation, but predominantly in those of MHG. The mutations were more frequent in double-hit lymphomas with IG as the MYC translocation partner, and were associated with higher MYC protein expression and poor patient survival. DLBCL with MYC/BCL2-DH and those with BCL2 translocation alone are most likely derived from follicular lymphoma or its precursor lesion, and acquisition of MYC pathogenic mutations may augment MYC function, resulting in aggressive clinical behaviour.
Electronic properties of the bulk and surface states of Fe1+yTe1−xSex
The idea of employing non-Abelian statistics for error-free quantum computing ignited interest in reports of topological surface superconductivity and Majorana zero modes (MZMs) in FeTe 0.55 Se 0.45 . However, the topological features and superconducting properties are not observed uniformly across the sample surface. The understanding and practical control of these electronic inhomogeneities present a prominent challenge for potential applications. Here, we combine neutron scattering, scanning angle-resolved photoemission spectroscopy, and microprobe composition and resistivity measurements to characterize the electronic state of Fe 1+ y Te 1− x Se x . We establish a phase diagram in which the superconductivity is observed only at sufficiently low Fe concentration, in association with distinct antiferromagnetic correlations, whereas the coexisting topological surface state occurs only at sufficiently high Te concentration. We find that FeTe 0.55 Se 0.45 is located very close to both phase boundaries, which explains the inhomogeneity of superconducting and topological states. Our results demonstrate the compositional control required for use of topological MZMs in practical applications. The compositional dependence of magnetic, superconducting and topological surface states on an iron-based superconductor is reported.
S-adenosylhomocysteine hydrolase inhibition by 3-deazaneplanocin A analogues induces anti-cancer effects in breast cancer cell lines and synergy with both histone deacetylase and HER2 inhibition
Epigenetic abnormalities including abnormal histone methyltransferase activity contribute to breast cancer pathogenesis. An example is over expression of the polycomb repressive complex (PRC) 2 member enhancer of zeste homolog 2 (EZH2) which is linked to epigenetic silencing and poor prognosis. Recent evidence shows that S-adenosylhomocysteine (AdoHcy) hydrolase inhibitors (AHI) such as 3-deazaneplanocin A (DZNep) modulate chromatin through indirect inhibition of histone methyltransferases including EZH2. We investigated the biological effects of AdoHcy hydrolase inhibition using DZNep and its structural analogues 3-deazaadenosine (DZA) and neplanocin A (Nep A) in breast cancer cells. EZH2 protein expression was decreased and dose dependent growth inhibition occurred with variable potencies in MCF7, MDA-MB-231 and SKBr3 breast cancer cells. Cellular proliferation was inhibited through G 2 /M cell cycle arrest and apoptosis. In addition breast cancer cells accumulated cytoplasmic lipid droplets in response to AdoHcy hydrolase inhibition consistent with a differentiating effect. Each analogue induced a similar pattern of biological activity against breast cancer cells but with differences in potency (DZA > DZNep > Nep A). Co-administration with the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) induced synergistic inhibition of breast cancer cell proliferation. Furthermore, the relatively AHI resistant human epidermal growth factor receptor 2 (HER2) positive cell line SKBr3 underwent synergistic growth inhibition in response to co-treatment with the HER2 directed therapeutic antibody trastuzumab. In conclusion, AHI induce growth inhibition, cell cycle arrest, apoptosis and differentiation in breast cancer cells and synergise with HDAC and HER2 inhibition. Targeting histone methyltransferase activity might be of therapeutic value in breast cancer.