The 21cm angular-power spectrum from the dark ages

At redshifts z >~ 30 neutral hydrogen gas absorbs CMB radiation at the 21cm spin-flip frequency. In principle this is observable and a high-precision probe of cosmology. We calculate the linear-theory angular power spectrum of this signal and cross-correlation between redshifts on scales much larger than the line width. In addition to the well known redshift-distortion and density perturbation sources a full linear analysis gives additional contributions to the power spectrum. On small scales there is a percent-level linear effect due to perturbations in the 21cm optical depth, and perturbed recombination modifies the gas temperature perturbation evolution (and hence spin temperature and 21cm power spectrum). On large scales there are several post-Newtonian and velocity effects; although negligible on small scales, these additional terms can be significant at l <~ 100 and can be non-zero even when there is no background signal. We also discuss the linear effect of reionization re-scattering, which damps the entire spectrum and gives a very small polarization signal on large scales. On small scales we also model the significant non-linear effects of evolution and gravitational lensing. We include full results for numerical calculation and also various approximate analytic results for the power spectrum and evolution of small scale perturbations.Comment: 29 pages; significant extensions including: self-absorption terms (i.e. change to background radiation due to 21cm absorption); ionization fraction perturbations; estimates of non-linear effects; approximate analytic results; results for sharp redshift window functions. Code available at http://camb.info/sources

Deteksi Distorsi Blok Pada Gambar Digital Terkompresi

Pada penelitian ini, dikemukakan sebuah metode baru berbasis analisis multiresolusi untuk mendeteksi distorsi blok pada gambar digital terkompresi. Gambar digital terkompresi cenderung memiliki artefak codingyang mungkin muncul ketika gambar dikodekan dengan tingkat kompresi yang tinggi. Penelitian ini berfokus pada distorsi blok yang dirasakan signifikan dalam gambar digital terkompresi berbasis blok seperti JPEG. Pada penelitian ini, transformasi Wavelet Haar digunakan untuk mendekomposisi sebuah gambar dan menganalisis karakteristik tepian dari gambar tersebut. Berdasarkan dekomposisi ini, peneliti menyusun sebuah algoritma untuk mendeteksi distorsi blok dengan menganalisis koefisien hasil transformasi wavelet. Hasil eksperimen algoritma terhadap database gambar LIVE menunjukkanhasil yang sangat memuaskan dengan tingkat kesalahan yang rendah. In this study, presented a new method based on multiresolution analysis to detect the distortion of the block in a compressed digital image. Compressed digital image tend to have coding artifacts that may arise when an image is encoded with a high compression rate. This study focuses on a block distortion that significantly perceived in the block-based compressed digital images such as JPEG. In this study, Wavelet Haar transformation is used to decompose an image and analyze the characteristics of the edge of the picture. Based on this decomposition, the researchers compiled an algorithm for detecting a block distortion by analyzing the coefficients of the wavelet transformation. The results of experimental algorithms for image database LIVE shows very satisfactory results with low error rates

P Wave Meson Spectrum in a Relativistic Model with Instanton Induced Interaction

On the basis of the phenomenological relativistic harmonic models for quarks we have obtained the masses of P wave mesons. The full Hamiltonian used in the investigation has Lorentz scalar + vector confinement potential, along with one gluon exchange potential (OGEP) and the instanton-induced quark-antiquark interaction (III). A good agreement is obtained with the experimental masses. The respective role of III and OGEP for the determination of the meson masses is discussed.Comment: Corrected typo

Growth and properties of ZnO:Al on textured glass for thin film solar cells

Aluminium induced texturing (AIT) method has been used to texture glass substrates in order to enhance the photon absorption in thin film solar cells. The resultant glass roughness has been analyzed by varying the AIT process parameters and it has been found that the deposition method of Al is a decisive factor in tuning the texture. Two types of textures, a soft (texture E) and a rough texture (texture S), were achieved from the thermally evaporated and sputtered Al layers through AIT process. Aluminium-doped zinc oxide (AZO) layers of different thickness were deposited over both textures and over smooth glass. Haze values above 30% were obtained for texture S+AZO and above 10% for texture E+AZO. The resultant morphologies were free from sharp edges or deep valleys and the transparency and the resistivity values were also good enough to be used as front contact for thin film solar cells. In order to demonstrate the light absorption enhancement in a solar cell device, 200 nm of a-Si:H followed by 300nm of Ag were grown over the textured and smooth substrates with AZO, and an optical absorption enhancement of 35% for texture E and 53% for texture S was obtained in comparison to the smooth substrate

Molecular-dynamics investigation of nanoburnishing process

It is well known that the burnishing process affects the surface characteristic, namely: surface roughness, surface hardness, wear resistance, fatigue resistance and increased maximum residual stress in compression. Unfortunately we still far from full understanding what parameters and mechanisms are responsible for the certain surface modification. That is why methods of computer modeling can be considered as useful tool to investigate surface changing during contact interaction as well as burnishing process. It is more essential if we consider processes are taking place at atomic scale level. In the paper we try to reproduce the details of burnishing process at nano-scale level. To investigate features of surface treatment we use the molecular dynamics simulation. Various pure crystalline materials were considered. Results of our modeling are very close to the experimental observatio

Neutron and proton drip lines using the modified Bethe-Weizsacker mass formula

Proton and neutron separation energies have been calculated using the extended Bethe-Weizsacker mass formula. This modified Bethe-Weizsacker mass formula describes minutely the positions of all the old and the new magic numbers. It accounts for the disappearance of some traditional magic numbers for neutrons and provides extra stability for some new neutron numbers. The neutron and proton drip lines have been predicted using this extended Bethe-Weizsacker mass formula. The implications of the proton drip line on the astrophysical rp-process and of the neutron drip line on the astrophysical r-process have been discussed.Comment: 5 pages, 2 figure

High-resolution and high-accuracy topographic and transcriptional maps of the nucleosome barrier.

Nucleosomes represent mechanical and energetic barriers that RNA Polymerase II (Pol II) must overcome during transcription. A high-resolution description of the barrier topography, its modulation by epigenetic modifications, and their effects on Pol II nucleosome crossing dynamics, is still missing. Here, we obtain topographic and transcriptional (Pol II residence time) maps of canonical, H2A.Z, and monoubiquitinated H2B (uH2B) nucleosomes at near base-pair resolution and accuracy. Pol II crossing dynamics are complex, displaying pauses at specific loci, backtracking, and nucleosome hopping between wrapped states. While H2A.Z widens the barrier, uH2B heightens it, and both modifications greatly lengthen Pol II crossing time. Using the dwell times of Pol II at each nucleosomal position we extract the energetics of the barrier. The orthogonal barrier modifications of H2A.Z and uH2B, and their effects on Pol II dynamics rationalize their observed enrichment in +1 nucleosomes and suggest a mechanism for selective control of gene expression

GENETIC REGULATION OF HUMAN FETAL LIVER AND ITS CLINICAL APPLICATION

Master'sMASTER OF SCIENC