An explanation of the ABC enhancement in the dd -> alpha X reaction at intermediate energies

The dd -> alpha X reaction is studied in a model where each pair of nucleons in the projectile and target deuterons undergoes pion production through the NN -> d pi reaction. The condition that the two deuterons fuse to form an alpha-particle then leads to peaks at small missing masses, the well-known ABC enhancement, but also a broad structure around the maximum missing mass. With a simplified input amplitude the model gives a quantitative description of both the alpha-particle momentum and angular distributions for a deuteron beam energy of 1250 MeV.Comment: 10 pages, Latex2e, 1 eps figure, submitted to Phys. Lett.

The Surface Coverage of Fat on Food Powders Analyzed by Esca (Electron Spectroscopy for Chemical Analysis)

ES.A (electron spectroscopy for chemical analysis) was used to estimate the fat coverage on different spray-dried food powder surfaces. The method presented here represents a new way of estimating the actual surface coverage of fat on a food powder. The ESCAmethod is illustrated with three different series of experimen ts. The results obtained with the ESCA-technique are combined with the results obtained from the conventional free fat extraction technique for different spray-dried powders. In the first series , emulsion s containing different ratios of protein to fat were spray-dried. An increase in the amount of fat in the emulsion gives an increased surface coverage of fat. Powders with a high fat content shows a high free fat level, indicating a continuous network of fat in side the particles. Secondly, the effect of heat treatment on the ability of bovine serum albumin to encapsulate fat has been investigated . The results show that albumin treated at high temperature encapsulates the fat less completely than the albumin treated at low temperature. Finally, emulsions containing oil phases with different melting points were spray-dried and analyzed. Powders with a high melting fat show very well encapsulated fat with only a minor surface coverage of fat. Powders with a qualitatively different distribution of fat can be identified by comparing the surface coverage of fat estimated by ESCA with the free fat measurements

Planar box diagram for the (N_F = 1) 2-loop QED virtual corrections to Bhabha scattering

In this paper we present the master integrals necessary for the analytic calculation of the box diagrams with one electron loop (N_{F}=1) entering in the 2-loop (\alpha^3) QED virtual corrections to the Bhabha scattering amplitude of the electron. We consider on-shell electrons and positrons of finite mass m, arbitrary squared c.m. energy s, and momentum transfer t; both UV and soft IR divergences are regulated within the continuous D-dimensional regularization scheme. After a brief overview of the method employed in the calculation, we give the results, for s and t in the Euclidean region, in terms of 1- and 2-dimensional harmonic polylogarithms, of maximum weight 3. The corresponding results in the physical region can be recovered by analytical continuation. For completeness, we also provide the analytic expression of the 1-loop scalar box diagram including the first order in (D-4).Comment: Misprints in Eqs. (36), (38), (39), and (B.9) have been corrected. The results are now available at http://pheno.physik.uni-freiburg.de/~bhabha, as FORM input file

Two-Loop N_F=1 QED Bhabha Scattering Differential Cross Section

We calculate the two-loop virtual, UV renormalized corrections at order \alpha^4 (N_F=1) in QED to the Bhabha scattering differential cross section, for arbitrary values of the squared c.m. energy s and momentum transfer t, and on-shell electrons and positrons of finite mass m. The calculation is carried out within the dimensional regularization scheme; the remaining IR divergences appear as polar singularities in (D-4). The result is presented in terms of 1- and 2-dimensional harmonic polylogarithms, of maximum weight 3.Comment: 61 pages, 4 figures. Overall sign mistakes in some formulas in appendix corrected, references adde

Two-Loop N_F =1 QED Bhabha Scattering: Soft Emission and Numerical Evaluation of the Differential Cross-section

Recently, we evaluated the virtual cross-section for Bhabha scattering in pure QED, up to corrections of order alpha^4 (N_F =1). This calculation is valid for arbitrary values of the squared center of mass energy s and momentum transfer t; the electron and positron mass m was considered a finite, non vanishing quantity. In the present work, we supplement the previous calculation by considering the contribution of the soft photon emission diagrams to the differential cross-section, up to and including terms of order alpha^4 (N_F=1). Adding the contribution of the real corrections to the renormalized virtual ones, we obtain an UV and IR finite differential cross-section; we evaluate this quantity numerically for a significant set of values of the squared center of mass energy s.Comment: 24 pages, 15 figures. Formulas in Appendix B corrected, changes in Section 3, references adde

Process intensification through integration of upstream perfusion cell culture with downstream continuous chromatography in monoclonal antibody production

Process intensification is gaining interest as a strategy to reduce production costs, while improving product quality and throughput in the manufacturing of biopharmaceuticals. For a competitive production process, continuous or semi-continuous upstream and downstream processing can be employed. Compared with a process performed in batch runs, continuous processing allows for increased capacity utilization and eliminates or minimized the need for intermediate hold-up steps. Here, we describe the integration of a high-performing upstream cell culture process with downstream purification utilizing new emerging technologies such as periodic counter-current (PCC) chromatography and straight-through processing (STP). A high-cell density perfusion process based on commercially available ActiCHO™ cell culture media was developed for a MAb-producing Chinese hamster ovary (CHO) cell line. Medium prototypes were evaluated in small scale using the single-use ReadyToProcess WAVE™ 25 bioreactor system. Medium optimization resulted in a final process with a cell-specific perfusion rate (CSPR) of less than 50 pL/cell/d. Process performance was verified at laboratory scale using single-use stirred-tank bioreactor systems. Productivity and product quality of the developed perfusion process were compared with a standard fed-batch process. MAb capture on MabSelect SuRe™ LX protein A chromatography medium (resin) was performed in a three-column PCC (3C PCC) setup. The capture step was followed by two polishing steps using Capto™ S ImpAct ion exchange and Capto adhere multimodal ion exchange media in serially connected columns in a STP setup. MAb purity and yield of the developed continuous processes were compared with traditional setups performed in batch runs. In this case study, we demonstrate the feasibility of integrated upstream and downstream MAb processing performed in a continuous manner. The developed process shows a performance equivalent to traditional processing performed in batch runs

Efficient approaches for perfusion medium development

Here, we present a fast and convenient strategy for developing a high-cell density perfusion process for antibody-producing Chinese hamster ovary (CHO) cells based on the commercially available ActiCHO™ Media System. ActiCHO P base medium was used as a starting point and ActiCHO Feed-A and Feed-B were added in various concentrations as supplements. The resulting perfusion medium prototypes were first evaluated in batch cultures, applying a design of experiment (DoE) strategy (Figure 1), and then tested in small-scale perfusion cultures in rocking single-use WAVE bioreactor™ systems (Figure 2). The medium optimization resulted in a final process with a cell-specific perfusion rate (CSPR) of less than 50 pL/cell/d, which is a more than 45% decrease compared with the starting process conditions. The performance of the perfusion process was further validated in lab-scale single-use stirred-tank bioreactor systems. Productivity and product quality of the perfusion process were compared with a standard fed-batch culture process

Two-loop QED Corrections to Bhabha Scattering

Recent developments in the calculation of the NNLO corrections to the Bhabha scattering differential cross section in pure QED are briefly reviewed and discussed.Comment: 5 pages, 4 figures, to appear in the proceedings of the 7th International Symposium on Radiative Corrections (RADCOR05), Shonan Village, Japan, 200