A new approach to improving the efficiency of fel oscillator simulations

During the last year we have been benchmarking FEL oscillator simulation codes against the measured performance of the three Jefferson Lab oscillator FELs. While one might think that a full 4D simulation is de facto the best predictor of performance, the simulations are computationally intensive, even when analytical approximations to the electron bunch longitudinal distribution are used. In this presentation we compare the predictions of the 4D FEL interaction codes Genesis and Medusa, in combination with the optical code OPC, with those using a combination of the 2D & 3D versions of these codes, which can be run quickly on a single CPU core desktop computer

Magnetoresistance and dephasing in a two-dimensional electron gas at intermediate conductances

We study, both theoretically and experimentally, the negative magnetoresistance (MR) of a two-dimensional (2D) electron gas in a weak transverse magnetic field $B$. The analysis is carried out in a wide range of zero-$B$ conductances $g$ (measured in units of $e^2/h$), including the range of intermediate conductances, $g\sim 1$. Interpretation of the experimental results obtained for a 2D electron gas in GaAs/In$_x$Ga$_{1-x}$As/GaAs single quantum well structures is based on the theory which takes into account terms of higher orders in $1/g$, stemming from both the interference contribution and the mutual effect of weak localization (WL) and Coulomb interaction. We demonstrate that at intermediate conductances the negative MR is described by the standard WL "digamma-functions" expression, but with a reduced prefactor $\alpha$. We also show that at not very high $g$ the second-loop corrections dominate over the contribution of the interaction in the Cooper channel, and therefore appear to be the main source of the lowering of the prefactor, $\alpha\simeq 1-2/\pi g$. We further analyze the regime of a "weak insulator", when the zero-$B$ conductance is low $g(B=0)<1$ due to the localization at low $T$, whereas the Drude conductance is high, $g_0>>1.$ In this regime, while the MR still can be fitted by the digamma-functions formula, the experimentally obtained value of the dephasing rate has nothing to do with the true one. The corresponding fitting parameter in the low-$T$ limit is determined by the localization length and may therefore saturate at $T\to 0$, even though the true dephasing rate vanishes.Comment: 36 pages, 16 figure

Singularities of bi-Hamiltonian systems

We study the relationship between singularities of bi-Hamiltonian systems and algebraic properties of compatible Poisson brackets. As the main tool, we introduce the notion of linearization of a Poisson pencil. From the algebraic viewpoint, a linearized Poisson pencil can be understood as a Lie algebra with a fixed 2-cocycle. In terms of such linearizations, we give a criterion for non-degeneracy of singular points of bi-Hamiltonian systems and describe their types

Magnetic trapping of an atomic 55Mn-52Cr mixture

Atomic manganese 55Mn and chromium 52Cr are simultaneously loaded and confined in a magnetic trap. Using a cryogenic 3 He buffer gas, 1011 manganese and 1012 chromium atoms are trapped at an initial temperature of 600 mK. The buffer gas is then pumped away, thermally isolating the sample. The Mn-Cr interspecies inelastic rate constant is measured to be GMn,Cr=1.5s±0.2d310−13 cm3 /s.Physic

Conductometric biosensor based on whole-cell microalgae for assessment of heavy metals in wastewater

Whole-cell Chlorella vulgaris conductometric biosensors consisting of gold planar interdigitated electrodes and sol-gel algal membranes have been used for assessment of heavy-metal ions in water. These analytes act as algal alkaline phosphatase inhibitors. Enzyme residual activity has been measured in Tris-nitrate buffer in the presence of Mg²⁺ ions as activator. Operating conditions of this biosensor have been optimized and its characteristics are discussed. Detection limits are about 1 ppb for Cd²⁺, Co²⁺, Ni²⁺, Pb²⁺ and 10 ppb for Zn²⁺. The storage stability of the biosensor in buffer solution at 4 oC is more than 40 days. The biosensor has been used to assess wastewater pollution.Описан биосенсор для оценки содержания тяжелых металлов в воде. Для его создания клетки Chlorella vulgaris иммобилизировали на золотых планарных гребенчатых электродах с помощью золь–гель технологии. Тяжелые металлы являются ингибиторами щелочной фосфатазы. Остаточную активность иммобилизованного фермента измеряли в трис-нитратном буферном растворе в присутствии активатора: ионов магния. Оптимизированы рабочие характеристики биосенсора. Нижняя граница определения составляла 1 млрд ⁻¹ для Cd²⁺, Co²⁺, Ni²⁺, Pb²⁺ и 10 млрд ⁻¹ для Zn²⁺. Срок хранения биосенсора в буферном растворе при температуре 4 оC составляет более 40 дней. Биосенсор использован для оценки загрязнения тяжелыми металлами сточных вод.Описано біосенсор для оцінки вмісту важких металів у воді. Для його створення клітини Chlorella vulgaris іммобілізували на золотих планарних гребінчастих електродах за допомогою золь–гель технології. Важкі метали є інгібіторами лужної фосфатази. Залишкову активність іммобілізованого ферменту вимірювали в трис-нітратному буферному розчині за присутності активатора – іонів магнію. Оптимізовано робочі характеристики біосенсора. Нижня межа визначення складала 1 млрд ⁻¹ для Cd²⁺, Co²⁺, Ni²⁺, Pb²⁺ та 10 млрд ⁻¹ для Zn²⁺. Термін зберігання біосенсора у буферному розчині за температури 4 оC був більшим, ніж 40 діб. Біосенсор використано для оцінки забруднення важкими металами стічних вод

Magnetoelectric ordering of BiFeO3 from the perspective of crystal chemistry

In this paper we examine the role of crystal chemistry factors in creating conditions for formation of magnetoelectric ordering in BiFeO3. It is generally accepted that the main reason of the ferroelectric distortion in BiFeO3 is concerned with a stereochemical activity of the Bi lone pair. However, the lone pair is stereochemically active in the paraelectric orthorhombic beta-phase as well. We demonstrate that a crucial role in emerging of phase transitions of the metal-insulator, paraelectric-ferroelectric and magnetic disorder-order types belongs to the change of the degree of the lone pair stereochemical activity - its consecutive increase with the temperature decrease. Using the structural data, we calculated the sign and strength of magnetic couplings in BiFeO3 in the range from 945 C down to 25 C and found the couplings, which undergo the antiferromagnetic-ferromagnetic transition with the temperature decrease and give rise to the antiferromagnetic ordering and its delay in regard to temperature, as compared to the ferroelectric ordering. We discuss the reasons of emerging of the spatially modulated spin structure and its suppression by doping with La3+.Comment: 18 pages, 5 figures, 3 table

Hypermethylation of the reelin (RELN) promoter in the brain of schizophrenic patients: A preliminary report

DNA methylation changes could provide a mechanism for DNA plasticity and dynamism for short-term adaptation, enabling a type of cell memory to register cellular history under different environmental conditions. Some environmental insults may also result in pathological methylation with corresponding alteration of gene expression patterns. Evidence from several studies has suggested that in schizophrenia and bipolar disorder, mRNA of the reelin gene (RELN), which encodes a protein necessary for neuronal migration, axonal branching, synaptogenesis, and cell signaling, is severely reduced in post-mortem brains. Therefore, we investigated the methylation status of the RELN promoter region in schizophrenic patients and normal controls as a potential mechanism for down regulation of its expression. Ten post-mortem frontal lobe brain samples from male schizophrenic patients and normal controls were obtained from the Harvard Brain Tissue Resources Center. DNA was extracted using a standard phenol-chloroform DNA extraction protocol. To evaluate differences between patients and controls, we applied methylation specific PCR (MSP) using primers localized to CpG islands flanking a potential cyclic AMP response element (CRE) and a stimulating protein-1 (SP1) binding site located in the promoter region. For each sample, DNA extraction, bisulfite treatment, and MSP were independently repeated at least four times to accurately determine the methylation status of the target region. Forty-three PCR trials were performed on the test and control samples. MSP analysis of the RELN promoter revealed an unmethylated signal in all reactions (43 of 43) using DNA from the frontal brain tissue, derived from either the schizophrenic patients or normal controls indicating that this region of the RELN promoter is predominantly unmethylated. However, we observed a distinct methylated signal in 73 of the trials (16 of 22) in schizophrenic patients compared with 24 (5 of 21) of controls. Thus, the hypermethylation of the CpG islands flanking a CRE and SP1 binding site observed at a significantly higher level (t = -5.07, P = 0.001) may provide a mechanism for the decreased RELN expression, frequently observed in post-mortem brains of schizophrenic patients. We also found an inverse relationship between the level of DNA methylation using MSP analysis and the expression of the RELN gene using semi-quantitative RT-PCR. Despite the small sample size, these studies indicate that promoter hypermethylation of the RELN gene could be a significant contributor in effecting epigenetic alterations and provides a molecular basis for the RELN gene hypoactivity in schizophrenia. Further studies with a larger sample set would be required to validate these preliminary observations. © 2005 Wiley-Liss, Inc

Transversity Form Factors and Generalized Parton Distributions of the pion in chiral quark models

The transversity Generalized Parton Distributions (tGPDs) and related transversity form factors of the pion are evaluated in chiral quark models, both local (Nambu--Jona-Lasinio) and nonlocal, involving a momentum-dependent quark mass. The obtained tGPDs satisfy all a priori formal requirements, such as the proper support, normalization, and polynomiality. We evaluate generalized transversity form factors accessible from the recent lattice QCD calculations. These form factors, after the necessary QCD evolution, agree very well with the lattice data, confirming the fact that the spontaneously broken chiral symmetry governs the structure of the pion also in the case of the transversity observables.Comment: 6 pages, 3 figures, presented by WB at LIGHTCONE 2011, 23 - 27 May, 2011, Dalla

Survival of metastatic melanoma patients after dendritic cell vaccination correlates with expression of leukocyte phosphatidylethanolamine-binding protein 1/Raf kinase inhibitory protein

Immunotherapy for metastatic melanoma offers great promise but, to date, only a subset of patients have responded. There is an urgent need to identify ways of allocating patients to the most beneficial therapy, to increase survival and decrease therapy-associated morbidity and costs. Blood-based biomarkers are of particular interest because of their straightforward implementation in routine clinical care. We sought to identify markers for dendritic cell (DC) vaccine-based immunotherapy against metastatic melanoma through gene expression analysis of peripheral blood mononuclear cells. A large-scale microarray analysis of 74 samples from two treatment centers, taken directly after the first round of DC vaccination, was performed. We found that phosphatidylethanolamine binding protein 1 (_PEBP1_)/ Raf Kinase inhibitory protein (RKIP) expression can be used to identify a significant proportion of patients who performed poorly after DC vaccination. This result was validated by q-PCR analysis on blood samples from a second cohort of 95 patients treated with DC vaccination in four different centers. We conclude that low _PEBP1_ expression correlates with poor overall survival after DC vaccination. Intriguingly, this was only the case for expression of _PEBP1_ after, but not prior to, DC vaccination. Moreover, the change in _PEBP1_ expression upon vaccination correlated well with survival. Further analyses revealed that _PEBP1_ expression positively correlated with genes involved in T cell responses but inversely correlated with genes associated with myeloid cells and aberrant inflammation including _STAT3, NOTCH1,_ and _MAPK1_. Concordantly, _PEBP1_ inversely correlated with the myeloid/ lymphoid-ratio and was suppressed in patients suffering from chronic inflammatory disease

Dilepton mass spectra in p+p collisions at sqrt(s)= 200 GeV and the contribution from open charm

The PHENIX experiement has measured the electron-positron pair mass spectrum from 0 to 8 GeV/c^2 in p+p collisions at sqrt(s)=200 GeV. The contributions from light meson decays to e^+e^- pairs have been determined based on measurements of hadron production cross sections by PHENIX. They account for nearly all e^+e^- pairs in the mass region below 1 GeV/c^2. The e^+e^- pair yield remaining after subtracting these contributions is dominated by semileptonic decays of charmed hadrons correlated through flavor conservation. Using the spectral shape predicted by PYTHIA, we estimate the charm production cross section to be 544 +/- 39(stat) +/- 142(syst) +/- 200(model) \mu b, which is consistent with QCD calculations and measurements of single leptons by PHENIX.Comment: 375 authors from 57 institutions, 18 pages, 4 figures, 2 tables. Submitted to Physics Letters B. v2 fixes technical errors in matching authors to institutions. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm