Decreased IL7Rα and TdT expression underlie the skewed immunoglobulin repertoire of human B-cell precursors from fetal origin

Newborns are unable to mount antibody responses towards certain antigens. This has been related to the restricted repertoire of immunoglobulin (Ig) genes of their B cells. The mechanisms underlying the restricted fetal Ig gene repertoire are currently unresolved. We here addressed this with detailed molecular and cellular analysis of human precursor-B cells from fetal liver, fetal bone marrow (BM), and pediatric BM. In the absence of selection processes, fetal B-cell progenitors more frequently used proximal V, D and J genes in complete IGH gene rearrangements, despite normal Ig locus contraction. Fewer N-nucleotides were added in IGH gene rearrangements in the context of low TdT and XRCC4 expression. Moreover, fetal progenitor-B cells expressed lower levels of IL7Rα than their pediatric counterparts. Analysis of progenitor-B cells from IL7Rα-deficient patients revealed that TdT expression and N-nucleotides additions in Dh-Jh junctions were dependent on functional IL7Rα. Thus, IL7Rα affects TdT expression, and decreased expression of this receptor underlies at least in part the skewed Ig repertoire formation in fetal B-cell precursors. These new insights provide a better understanding of the formation of adaptive immunity in the developing fetus

Modeling optical properties of particles with small-scale surface roughness: combination of group theory with a perturbation approach

A T-matrix method for scattering by particles with small-scale surface roughness is presented. The method combines group theory with a perturbation expansion approach. Group theory is found to reduce CPU-time by 4-6 orders of magnitude. The perturbation expansion extends the range of size parameters by a factor of 5 compared to non-perturbative methods. An application to optically hard particles shows that small-scale surface roughness changes scattering in side- and backscattering directions, and it impacts the single-scattering albedo. This can have important implications for interpreting remote sensing observations, and for the climate impact of mineral aerosols

Light Scattering Properties of Higher Order Chebyshev Particles and Implications for Aerosols with a Weak Surface Roughness

Chebyshev particles of comparatively low orders n are used in the past to study the effects of nonspherical but concave geometries in remote sensing applications. Their shape is given by r(theta) = r0 * [1 + a * cos(n * theta)] where r0 is the radius of the underlying sphere and a denotes the deformation parameter. We present results of light scattering computations for several Chebyshev particles characterized by higher orders n. Accurate results can be obtained for such particles within a T matrix approach. Moreover the scattering characteristics converge to stable results if the order is increased. Essential differences between, e.g., the phase functions of the higher order Chebyshev particles and the underlying regular scatterers can be observed. In particular an increased backscattering due to the surface roughness is obtained. This behavior is even more pronounced in the case of highly absorbing particles. The effects obtained agree with results of other approaches and correspond to expectations for particles with a weak surface roughness. This demonstrates that, on one hand, higher order Chebyshev particles can be used to estimate the influence of a weak surface roughness on the light scattering behavior of atmospheric aerosols. On the other hand, the consideration of roughness effects is important in the retrieval of aerosol properties

Violation of a Bell-like inequality by a combination of Rayleigh scattering with a Mach-Zehnder setup

In this paper I propose a classical optics experiment that results in a maximum violation of a Bell-like inequality. The first part is concerned with the Bell-like inequality (the so-called CHSH-inequality) itself. Its importance and its maximum violation in Quantum Mechanics (QM) are discussed in detail by employing an abstract probability state concept in a 4-dim. but classical event space. A T-matrix that represents the integral part of a corresponding Green's function as well as a statistical operator that contains a negative quasi-probability can be related to the corresponding quantum mechanical experiment. It is demonstrated that the derivation and usage of the T-matrix and the Green's function are equivalent to what is known from classical scattering theory. It is shown moreover that the negative quasi-probability of the statistical operator may be interpreted as a sink of probabilities related to two single events of the considered 4-dim. event space. A necessary condition for the violation of the CHSH-inequality is derived and discussed afterwards. In the second part of this paper I discuss a modification of the 4-dim. event space considered in the first part. It is shown that a combination of conventional Rayleigh scattering with a Mach-Zehnder setup would be able to put this modification into practice. Thus it becomes possible to achieve a maximum violation of the CHSH-inequality, if formulated in terms of intensities, on a pure classical way. The combination of classical light scattering with correlation experiments such as proposed in this paper may open new ways to study and to use the violation of Bell-like inequalities in modern optics

On the Independent Scattering Assumption in the Electromagnetic and Acoustic Case

The assumption of independent scattering is of some importance in a variety of different scattering scenarios not only in the realm of remote sensing but also in technical and medical diagnostics. This assumption is related to an ensemble of scattering particles within an illuminated volume element. Its justification requires the consideration of two different effects. These are the interference of the scattered fields produced by -, and the scattering interaction between different particles of the ensemble. In our investigations, we consider the simplest ensembles consisting of two and three particles. When dealing with plane electromagnetic wave scattering, the program mstm by Mackowski and Mishchenko (Mackowski D. W. and Mishchenko M. I., “A multiple sphere T-matrix Fortran code for use on parallel computer clusters,” J. Quant. Spectrosc. Radiat. Transfer 112, 2182, 2011) is used. Note that this program is based on a T-matrix approach. The ensemble T-matrix is obtained by an iterative solution of an interaction equation system. Setting the number of iterations to zero results in a solution where no scattering interactions between the spherical particles are taken into account. However interference effects remain. In this way, the two different aspects of the independent scattering assumption – the interference and the scattering interaction – can be studied separately. To deal with plane acoustic wave scattering, an own T-matrix program has been developed. It also allows a separate investigation of above both aspects. In our contribution we discuss conditions under which the scattering interaction between the particles can be neglected. We show that even under these conditions and if averaging over the particle distances, the overall scattering behavior of the ensembles cannot be described by a simple sum over those of the single isolated particles. In analogy to the double and triple slit experiments, interference effects remain in the forward scattering direction. Depending on the particle configuration, interference effects can be also observed in the backscattering direction. We show furthermore that they are attenuated by particle interactions only to a certain degree. It is therefore concluded that in scattering measurements that are based on coherent incident fields (such as Lidar and Radar measurements) the violation of the independent scattering assumption in the near forward and backward direction has to be considered as a potential source of errors in the data analysis