Collective character of spin excitations in a system of Mn2+^{2+} spins coupled to a two-dimensional electron gas

We have studied the low energy spin excitations in n-type CdMnTe based dilute magnetic semiconductor quantum wells. For magnetic fields for which the energies for the excitation of free carriers and Mn spins are almost identical an anomalously large Knight shift is observed. Our findings suggests the existence of a magnetic field induced ferromagnetic order in these structures, which is in agreement with recent theoretical predictions [J. K{\"o}nig and A. H. MacDonald, submitted Phys. Rev. Lett. (2002)]Comment: 4 figure

Field #3 of the Palomar-Groningen Survey II. Near-infrared photometry of semiregular variables

Near-infrared photometry (JHKL'M) was obtained for 78 semiregular variables (SRVs) in field #3 of the Palomar-Groningen survey (PG3, l=0, b=-10). Together with a sample of Miras in this field a comparison is made with a sample of field SRVs and Miras. The PG3 SRVs form a sequence (period-luminosity & period-colour) with the PG3 Miras, in which the SRVs are the short period extension to the Miras. The field and PG3 Miras follow the same P/(J--K)o relation, while this is not the case for the field and PG3 SRVs. Both the PG3 SRVs and Miras follow the SgrI period-luminosity relation adopted from Glass et al. (1995, MNRAS 273, 383). They are likely pulsating in the fundamental mode and have metallicities spanning the range from intermediate to approximately solar.Comment: 14 pages LaTeX (2 tables, 8 figures), to appear in A&A 338 (1998); minor modifications in tex

The Stellar Population of the M31 Spiral Arm Around OB Association A24

A study of the stellar population of the M31 spiral arm around OB association A24 was carried out based on the photometric data obtained from deep V and JHK imaging. The luminosity function was obtained for -7 <~ Mbol <~ -3.5 by applying the extinction correction corresponding to Av=1 and the bolometric correction BC(K) as an empirical function of (J-K)o. In comparing the observed color-luminosity diagrams with semitheoretical isochrones modified for the dust-shell effects, we found the young population of t <~ 30 Myr with supergiants of Mbol <~ -5, the bulk of the intermediate-age population of t ~ 0.2 - 2.5 Gyr with bright asymptotic giant branch (AGB) stars of -5 <~ Mbol <~ -4, and old populations of t ~> 3 Gyr with AGB and red giant branch (RGB) stars of Mbol ~> -4. The average star formation rate was estimated to be ~1.8x10^4 M_o/Myr and ~0.7x10^4 M_o/Myr per deprojected disk area of 1 kpc^2 from the number density of B0 V stars around Mv=-4.0 (age ~10 Myr) and the number density of bright AGB stars around Mbol = -4.3 (age ~1 Gyr), respectively. A study of the local variation in the V and the J and H luminosity functions revealed a kind of anticorrelation between the population of the young component and that of the intermediate-age component when subdomains of ~100 pc scales were concerned. This finding suggests that the disk domain around the A24 area experienced a series of star formation episodes alternatively among different subdomains with a timescale of a few spiral passage periods. Brief discussions are given about the interstellar extinction and about the lifetimes of bright AGB stars and the highly red objects (HROs) in the same area.Comment: 27 pages, 11 figures, accepted: ApJ, July 1, 199

Near-Infrared Properties of Metal-poor Globular Clusters in the Galactic Bulge Direction

Aims. J, H, and K' images obtained from the near-infrared imager CFHTIR on the Canada-France-Hawaii Telescope are used to derive the morphological parameters of the red giant branch (RGB) in the near-infrared color-magnitude diagrams for 12 metal-poor globular clusters in the Galactic bulge direction. Using the compiled data set of the RGB parameters for the observed 12 clusters, in addition to the previously studied 5 clusters, we discuss the properties of the RGB morphology for the clusters and compare them with the calibration relations for the metal-rich bulge clusters and the metal-poor halo clusters. Methods. The photometric RGB shape indices such as colors at fixed magnitudes of MK = MH = (-5.5, -5, -4, and -3), magnitudes at fixed colors of (J - K)o = (J - H)o = 0.7, and the RGB slope are measured from the fiducial normal points defined in the near- infrared color-magnitude diagrams for each cluster. The magnitudes of RGB bump and tip are also estimated from the differential and cumulative luminosity functions of the selected RGB stars. The derived RGB parameters have been used to examine the overall behaviors of the RGB morphology as a function of cluster metallicity. Results. The correlations between the near-infrared photometric RGB shape indices and the cluster metallicity for the programme clusters compare favorably with the previous observational calibration relations for metal-rich clusters in the Galactic bulge and the metal-poor halo clusters. The observed near-infrared magnitudes of the RGB bump and tip for the investigated clusters are also in accordance with the previous calibration relations for the Galactic bulge clusters.Comment: 12 pages, 9 figures, accepted for publication in Astronomy & Astrophysic

PENGUJIAN HIPOTESIS RATA-RATA BERURUT UNTUK MEMBANDINGAN TINGKAT KEBOCORAN DI DAERAH DINDING GINGIVAL MENGGUNAKAN TIGA MACAM BAHAN TAMBALAN SEMENTARA (Pendekatan Parametrik)

Jika melalui suatu eksperimen, ingin dibuktikan bahwa efek dari perlakuan membentuk sebuah urutan dengan hipotesis, HB1B : μ1 ≤ ... ≤ μk untuk menguji hipotesis tersebut digunakan statistik uji berbentuk : Σ Σ = = = − = − k j t k o m j k j j k o t T n y s N y y s j j 1 2 2 [ ] [1, ] 1 [ ] 2 2 [1, ] [μˆ ] / [ ] / dengan Σ Σ = = = − + k j k j o j j k j j s n y y n s 1 1 2 2 [1, ] 2 [ ] daerah kritis T C k ≥ , dengan C ditentukan melalui [ ] Σ= − − = ≥ k m m k m n m p P C 2 , [( 1) / 2,( ) / 2] α β .... (*) Variat [m−1) / 2,(n−m) / 2] β dalam persamaan (*) berdistribusi Beta dengan parameter(m-1)/2 dan (n-m)/2. Apabila σ 2 diketahui , statistik uji di atas diperoleh dengan mengganti 2 0 s oleh σ 2 dalam TBk B dan distribusi Beta oleh Distribusi χ 2 dengan dk = m-1 ( Chacko, 1963

OPTIMALISASI MASALAH PENJADWALAN PROYEK PEMBANGUNAN MENGGUNAKAN METODE PERT CPM

Proyek merupakan suatu rangkaian pekerjaan yang diadakan dalam selang waktu tertentu dan mempunyai tujuan khusus. Perbedaan proyek dengan pekerjaan lain terdapat pada keberadaannya yang tidak bersifat rutin, sehingga pengelolaannya memerlukan perhatian lebih. Salah satu hal yang sangat mempengaruhi keberhasilan proyek adalah pada perencanaan jadwal. Penelitian ini bertujuan untuk mengurangi resiko kegagalan dalam proyek dengan perencanaan penjadwalan pembangunan TK Pembina Kecamatan Johan Pahlawan Kabupaten Aceh Barat. Dalam penelitian ini menggunakan metode PERT (Project Evaluation and Review Technique)&nbsp; untuk mengetahui peluang penyelesaian proyek sebelum waktu terjadwal dan CPM (Critical Path Method) untuk mengetahui kegiatan-kegiatan kritis yang harus dilakukan sesuai jadwal tanpa adanya penundaan. Hasil dari CPM adalah kegiatan kritis yaitu B-F-I-J-K-O-Q-T-W-X-AK-AM dengan durasi selama 160 hari dan peluang penyelesaian proyek dari analisis PERT yaitu sebesar 43.86%. Hasil penjadwalan proyek disajikan dalam Diagram Gantt

Entropy and Graphs

The entropy of a graph is a functional depending both on the graph itself and on a probability distribution on its vertex set. This graph functional originated from the problem of source coding in information theory and was introduced by J. K\"{o}rner in 1973. Although the notion of graph entropy has its roots in information theory, it was proved to be closely related to some classical and frequently studied graph theoretic concepts. For example, it provides an equivalent definition for a graph to be perfect and it can also be applied to obtain lower bounds in graph covering problems. In this thesis, we review and investigate three equivalent definitions of graph entropy and its basic properties. Minimum entropy colouring of a graph was proposed by N. Alon in 1996. We study minimum entropy colouring and its relation to graph entropy. We also discuss the relationship between the entropy and the fractional chromatic number of a graph which was already established in the literature. A graph $G$ is called \emph{symmetric with respect to a functional $F_G(P)$} defined on the set of all the probability distributions on its vertex set if the distribution $P^*$ maximizing $F_G(P)$ is uniform on $V(G)$. Using the combinatorial definition of the entropy of a graph in terms of its vertex packing polytope and the relationship between the graph entropy and fractional chromatic number, we prove that vertex transitive graphs are symmetric with respect to graph entropy. Furthermore, we show that a bipartite graph is symmetric with respect to graph entropy if and only if it has a perfect matching. As a generalization of this result, we characterize some classes of symmetric perfect graphs with respect to graph entropy. Finally, we prove that the line graph of every bridgeless cubic graph is symmetric with respect to graph entropy.Comment: 89 pages, 4 figures, MMath Thesi