Non-Tachyonic Semi-Realistic Non-Supersymmetric Heterotic String Vacua

The heterotic--string models in the free fermionic formulation gave rise to some of the most realistic string models to date, which possess N=1 spacetime supersymmetry. Lack of evidence for supersymmetry at the LHC instigated recent interest in non-supersymmetric heterotic-string vacua. We explore what may be learned in this context from the quasi--realistic free fermionic models. We show that constructions with a low number of families give rise to proliferation of a priori tachyon producing sectors, compared to the non--realistic examples, which typically may contain only one such sector. The reason being that in the realistic cases the internal six dimensional space is fragmented into smaller units. We present one example of a quasi--realistic, non--supersymmetric, non--tachyonic, heterotic--string vacuum and compare the structure of its massless spectrum to the corresponding supersymmetric vacuum. While in some sectors supersymmetry is broken explicitly, i.e. the bosonic and fermionic sectors produce massless and massive states, other sectors, and in particular those leading to the chiral families, continue to exhibit fermi-bose degeneracy. In these sectors the massless spectrum, as compared to the supersymmetric cases, will only differ in some local or global U(1) charges. We discuss the conditions for obtaining $n_b=n_f$ at the massless level in these models. Our example model contains an anomalous U(1) symmetry, which generates a tadpole diagram at one loop-order in string perturbation theory. We speculate that this tadpole diagram may cancel the corresponding diagram generated by the one-loop non-vanishing vacuum energy and that in this respect the supersymmetric and non-supersymmetric vacua should be regarded on equal footing. Finally we discuss vacua that contain two supersymmetry generating sectors.Comment: 31 pages. 10 tables. Minor corrections. Tables are amended. Published versio

Monolayer honeycomb structures of group IV elements and III-V binary compounds

Using first-principles plane wave calculations, we investigate two dimensional honeycomb structure of Group IV elements and their binary compounds, as well as the compounds of Group III-V elements. Based on structure optimization and phonon mode calculations, we determine that 22 different honeycomb materials are stable and correspond to local minima on the Born-Oppenheimer surface. We also find that all the binary compounds containing one of the first row elements, B, C or N have planar stable structures. On the other hand, in the honeycomb structures of Si, Ge and other binary compounds the alternating atoms of hexagons are buckled, since the stability is maintained by puckering. For those honeycomb materials which were found stable, we calculated optimized structures, cohesive energies, phonon modes, electronic band structures, effective cation and anion charges, and some elastic constants. The band gaps calculated within Density Functional Theory using Local Density Approximation are corrected by GW0 method. Si and Ge in honeycomb structure are semimetal and have linear band crossing at the Fermi level which attributes massless Fermion character to charge carriers as in graphene. However, all binary compounds are found to be semiconductor with band gaps depending on the constituent atoms. We present a method to reveal elastic constants of 2D honeycomb structures from the strain energy and calculate the Poisson's ratio as well as in-plane stiffness values. Preliminary results show that the nearly lattice matched heterostructures of ...Comment: 12 Pages, 7 Figures, 1 Table; http://link.aps.org/doi/10.1103/PhysRevB.80.15545

Case Report: Labial Veneer All Porcelain with Press Method for Improving Aesthetic on Patient with Central Diastema Case

Patients with central diastema disorders often feel shame and less of confident. The disorder can be repaired by a Labial veneer restoration. This restoration is an improvement in the form of a layer on the labial surface of the tooth selected because it gives satisfactory aesthetic results and maintains the tooth structure. At this time, the method of fabricating labial veneer all porcelain growing rapidly, such as making labial veneer all porcelain with base layer using press method like all porcelain E-max press. This paper aims to determine the stages and problem solving of the difficulties that arise in the procedure of fabricating labial veneer all porcelain with the basic layer of labial veneer using press method. The method is based on working model done in dental laboratory, starting from work model preparation, wax contouring (wax up), Sprueing, Investing, Preheating, Pressing, Divesting, Cutting sprue and Build-up porcelain. Results obtained from making this labial veneer all porcelain is a tightly closed diastema that forms a contact of the field, smooth and glossy surface and good aesthetic

Studi Tentang Pengaruh Hari Perdaganganterhadap Return Saham Pada Bursa Efek Indonesia

Penelitian ini bertujuan untuk menguji pengaruh hari perdagangan terhadap return sahamserta fenomena-fenomena yang berkaitan denganday of the week effect, yakni Monday effect, weekfour effect dan Rogalski effect. Populasi dalam penelitian ini adalah Perusahaan yang terdaftar dalam Indeks Saham LQ-45 di Bursa Efek Indonesia selama periode Januari – Desember 2014.Teknik pengambilan sampel menggunakan metode purposive sampling.Data yang digunakan dalam penelitian ini adalah data sekunder, diperoleh dari informasi yang tersedia di Bursa Efek Indonesia. Pengumpulan data dilakukan dengan studi dokumentasi.Metode yang digunakan adalah metode analisis deskriptif dan metode analisis statistik. Hasil pengujian dalam penelitian ini menunjukkan bahwa hari perdagangan tidak berpengaruh signifikan terhadap return saham harian pada Bursa Efek Indonesia tahun 2014. Hal ini tidak membuktikan bahwa terjadi fenomena day of week effect di Bursa Efek Indonesia, dimana return terendah terjadi pada hari Senin dan return tertinggi terjadi pada hari Selasa. Hasil empiris ini juga tidak membuktinya terjadinya Monday Effect pada Bursa Efek Indonesia pada tahun 2014. Fenomena week four effect juga tidak berhasil ditemukan pada Bursa Efek Indonesia pada tahun 2014, dimana return negatif signifikan terjadi pada hari Senin minggu keempat dan kelima setiap akhir bulan. Penelitian ini juga tidak berhasil menemukan bukti terjadinya adanya Rogalski Effect pada bulan April diBursa Efek Indonesia pada tahun 2014

Ballisticity of nanotube FETs: Role of phonon energy and gate bias

We investigate the role of electron-phonon scattering and gate bias in degrading the drive current of nanotube MOSFETs. Our central results are: (i) Optical phonon scattering significantly decreases the drive current only when gate voltage is higher than a well-defined threshold. It means that elastic scattering mechanisms are most detrimental to nanotube MOSFETs. (ii) For comparable mean free paths, a lower phonon energy leads to a larger degradation of drive current. Thus for semiconducting nanowire FETs, the drive current will be more sensitive than carbon nanotube FETs because of the smaller phonon energies in semiconductors. (iii) Radial breathing mode phonons cause an appreciable reduction in drive current.Comment: 16 pages, 1 table, 4 figure

Peningkatan Keterampilan Generik Sains Dan Penguasaan Konsep Melalui Laboratorium Virtual Bebasis Inkuiri

Penelitian ini bertujuan untuk mengetahui peningkatan keterampilan generik sains dan penguasaan konsep pada materi arus listrik searah serta memperoleh gambaran respon mahasiswa terhadap penggunaan laboratorium virtual berbasis inkuiri. Penelitian ini dilakukan dengan metode pre-eksperimental design melalui one group pretest-posttest design yang dilaksanakan di Prodi Pendidikan Fisika Fakultas Tarbiyah dan Keguruan UIN Ar-Raniry Banda Aceh. Sampel yang terpilih menggunakan teknik porposive sampling yaitu angkatan 2014 unit 2 yang dijadikan kelas eksperimen. Pengumpulan data dilakukan dengan pretest dan posttest untuk mengetahui peningkatan keterampilan generik sains dan penguasaan konsep, lembar observasi untuk mengamati aktivitas mahasiswa selama proses pembelajaran, serta angket untuk mengetahui tanggapan mahasiswa terhadap penggunaan laboratorium virtual berbasis inkuiri. Hasil uji normalitas menunjukkan bahwa data N-gain berdistribusi normal. Persentase N-gain keterampilan generik sains tertinggi terjadi pada indikator kesadaran tentang skala sebesar 60% dengan kategori sedang dan terendah terjadi pada indikator pemodelan sebesar 27,81% dengan kategori rendah. Persentase rata-rata penguasaan konsep N-gain tertinggi pada sub konsep kuat arus dan beda potensial listrik sebesar 62,72% dan yang terendah pada sub konsep rangkaian hambatan listrik sebesar 33,33%. Mahasiswa memberikan tanggapan positif terhadap penggunaan laboratorium virtual berbasis inkuiri. Dapat disimpulkan penggunaan laboratorium virtual berbasis inkuiri dapat meningkatkan keterampilan generik sains dan penguasaan konsep

PENGEMBANGAN MODEL PERMAINAN GERAK DASAR LEMPAR UNTUK SISWA KELAS V SDN TAWANGARGO 4 KARANGPLOSO MALANG

Penelitian ini bertujuan mengembangkan permainan gerak dasar lempar bagi siswa kelas V di SDN Tawangargo 4 Karangploso Kabupaten Malang Jawa Timur. Metode penelitian yang digunakan adalah penelitian dan pengembangan dengan model konseptual. Prosedur  penelitian meliputi: analisis kebutuhan, pengembangan produk, dan uji coba produk. Teknik analisis data yang digunakan adalah analisis data kualitatif dan kuantitatif. Hasil penelitian menunjukkan bahwa produk ini valid digunakan siswa kelas V di SDN Tawangargo 4 Karangploso Kabupaten Malang. Hasil uji coba kelompok kecil dan kelompok besar mendapat rata-rata persentase 89,26%. Angka tersebut menunjukkan bahwa model permainan ini praktis digunakan oleh siswa kelas V di SD dan efektif meningkatkan gerak dasar lempar kelas V SD. Kata Kunci: model permainan, gerak dasar lempar, siswa SD