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Search Results: 1 - 10 of 297503 matches for " J. Jochum "
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Results from the CRESST Dark Matter Search at Gran Sasso
J. Jochum,CRESST Collaboration
Physics , 2000, DOI: 10.1134/1.855777
Abstract: We present the current status of CRESST(Cryogenic Rare Event Search using Superconducting Thermometers) project and new results concerning the development of new detectors based on the simultaneous measurement of phonons and scintillation light. A significant reduction in the background rate could recently be achieved. With our newly developed method for the simultaneous measurement of scintillation light, strong background discrimination is possible also in larger detectors, resulting in a substantial increase in WIMP detection sensitivity.
The scalar Singlet-Triplet Dark Matter Model
Oliver Fischer,Jochum J. van der Bij
Physics , 2013, DOI: 10.1088/1475-7516/2014/01/032
Abstract: We consider a model for cold dark matter, which combines a real scalar singlet and a real scalar $SU(2)_L$ triplet field, both of which are residing in the odd representation of a global $Z_2$ symmetry. The parameter space of the model is constrained by the inferred dark matter abundance from the WMAP and Planck data, the most recent results from the direct dark matter search experiment LUX, the Z boson decay width from LEP-I and perturbativity of the coupling parameters. The phenomenology of the remaining parameter space is studied. We find that the model allows for DM masses near the electroweak scale and a variety of decay scenarios.
HIV-infection during treatment of a chronic hepatitis B virus infection: implications for PrEP?
J Storim,C Jochum,J Timm,D Schadendorf
Journal of the International AIDS Society , 2012, DOI: 10.7448/ias.15.6.18169
Abstract: The protective effect of oral tenofovir disoproxil fumarate (TDF) with or without emtricitabine (FTC) as pre-exposure prophylaxis (PrEP) against HIV differed significantly among clinical studies and poor PrEP-adherence was closely associated with PrEP-failure. Despite HIV-infections during PrEP-exposure the development of resistance mutations against PrEP was rarely observed so far. As PrEP is an emerging tool against HIV transmission, it is important to identify risk-factors for PrEP-failure and the induction of PrEP-associated resistance mutations against antiretroviral drugs. We here present the case of a 25-year old MSM who was successfully treated with TDF due to a chronic hepatitis B virus (HBV) infection (HBV-DNA always <357 IU/ml after ten months of treatment). As HIV tests were negative when the treatment was initiated and six months later, no routine HIV tests were performed although the patient repetitively acquired sexually transmitted infections (STI). After 30 months, an HIV infection (subtype B) was diagnosed during a syphilis re-infection. At this point, HIV was TDF-resistant (K65R and A62V mutations within the reverse transcriptase gene). Retrospective analysis of frozen serum samples revealed HIV-seroconversion 12 months prior to diagnosis and low HIV-RNA levels from seroconversion to diagnosis (always <400 copies/ml). The TDF-based therapy of the chronic HBV-infection resembles a TDF-HIV-PrEP. But here poor therapy adherence is an unlikely cause for the 'PrEP-failure' as the constantly suppressed HBV-DNA indicates therapeutic TDF-levels over years. Combining TDF with FTC might have augmented the prophylactic effect. However, TDF-levels in the rectal mucosa are high and should therefore protect MSM who practice receptive anal intercourse. On the other hand, the concomitant STI of our patient may have promoted HIV transmission (via compromising the mucosal barrier function and promoting inflammatory reactions) and therefore possibly counteracted TDF-effects. Finally, infection with a TDF-resistant virus strain might explain the lack of protection in this case. But K65R is a rarely transmitted drug resistance mutation and low level viremia for one year suggests considerable TDF effectiveness. In fact, we here rather present a K65R mutation induced by a PrEP-like TDF therapy. The development of the K65R mutation in a PrEP-like situation emphasizes the urgent need of regular HIV-tests during PrEP exposure.
Neonatology/Paediatrics – Guidelines on Parenteral Nutrition, Chapter 13
Fusch, C.,Bauer, K.,B?hles, H. J.,Jochum, F.
GMS German Medical Science , 2009,
Abstract: There are special challenges in implementing parenteral nutrition (PN) in paediatric patients, which arises from the wide range of patients, ranging from extremely premature infants up to teenagers weighing up to and over 100 kg, and their varying substrate requirements. Age and maturity-related changes of the metabolism and fluid and nutrient requirements must be taken into consideration along with the clinical situation during which PN is applied. The indication, the procedure as well as the intake of fluid and substrates are very different to that known in PN-practice in adult patients, e.g. the fluid, nutrient and energy needs of premature infants and newborns per kg body weight are markedly higher than of older paediatric and adult patients. Premature infants <35 weeks of pregnancy and most sick term infants usually require full or partial PN. In neonates the actual amount of PN administered must be calculated (not estimated). Enteral nutrition should be gradually introduced and should replace PN as quickly as possible in order to minimise any side-effects from exposure to PN. Inadequate substrate intake in early infancy can cause long-term detrimental effects in terms of metabolic programming of the risk of illness in later life. If energy and nutrient demands in children and adolescents cannot be met through enteral nutrition, partial or total PN should be considered within 7 days or less depending on the nutritional state and clinical conditions.
Neutron Activation of 74Ge and 76Ge
Meierhofer G.,Canella L.,Grabmayr P.,Jochum J.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/20100205002
Abstract: The upcoming GERDA and MAJORANA experiments will use germanium crystals, isotopically enriched in 76Ge to search for the neutrinoless double beta decay (0ν2β). The very long half-life of 0ν2β (> 1025 y for 76Ge) requires an extremely low background level. Neutrons induced by cosmic muons can be captured after thermalization by 74Ge or 76Ge, followed by β -decay of 75Ge and 77Ge respectively. The prompt γ-cascade after neutron capture and the β-decay contribute to the total backround in these experiments. For a good estimation of the background the poorly known cross-sections for the 74Ge(n,γ)75,75mGe reactions were measured using targets, isotopically depleted in 76Ge. Furthermore the prompt γ-rays in 77Ge were measured with isotopically enriched germanium targets. The results of the latter measurement were combined with the results of a dedicated coincidence measurement to reconstruct the prompt γ-ray decay scheme.
Low temperature light yield measurements in NaI and NaI(Tl)
C. Sailer,B. Lubsandorzhiev,C. Strandhagen,J. Jochum
Physics , 2012, DOI: 10.1140/epjc/s10052-012-2061-7
Abstract: The scintillation light output of a pure and a Thallium doped Sodium Iodide (NaI) crystal under irradiation with 5.486MeV \alpha -particles has been measured over a temperature range from 1.7K to 300K. Estimates of the decay time constant at three selected temperatures are given. For pure NaI an increase in light yield towards low temperatures could be confirmed and measured at higher precision. For NaI(Tl) below 60K an increase in light output has been found.
Neutron Flux at the Gran Sasso Underground LaboratoryRevisited
H. Wulandari,J. Jochum,W. Rau,F. von Feilitzsch
Physics , 2003, DOI: 10.1016/j.astropartphys.2004.07.005
Abstract: The neutron flux induced by radioactivity at the Gran Sasso underground laboratory is revisited. We have performed calculations and Monte Carlo simulations; the results offer an independent check to the available experimental data reported by different authors, which vary rather widely. This study gives detailed information on the expected spectrum and on the variability of the neutron flux due to possible variations of the water content of the environment.
Neutron Background Studies for the CRESST Dark Matter Experiment
H. Wulandari,J. Jochum,W. Rau,F. von Feilitzsch
Physics , 2004,
Abstract: The new detection concept applied for the direct WIMP search experiment CRESST II, which enables a clear discrimination between electron recoils and nuclear recoils, will leave neutrons as the main background. This background will soon limit the sensitivity of the experiment and therefore become an important issue for the next phase of CRESST. We have performed a study based on Monte Carlo simulations to investigate how neutrons from different origins affect CRESST and which measures have to be taken to reach the projected sensitivity.
Der Souver n
Uwe Jochum
Libreas : Library Ideas , 2009,
Uwe Jochum
Libreas : Library Ideas , 2006,
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