Konsep Agama Suku Wana Tentang Kematian, Implikasinya Bagi Misi Kristen di Wana

Wana, one of the tribes in Central Sulawesi, has a custom of demolishing houses and moving when one of the inhabitants dies. This custom is an expression of their fear of death. In theory, cultural activities around death are always associated with religious concepts. This study aims to explore the religious ideas behind their habits. The research method used was an ethnographic study using an interview as data collection techniques. Informants are 8 (eight) original Wana people. Data is analyzed through reduction, display, and conclusions/verification. The results show that the custom is related to the religious concept they professed regarding death. According to the Wana, death is related to Pue, the end of everything, and caused by evil spirits. The Purpose of dismantling the house and moving after death is to avoid the influence of evil spirits against the living. For Christian mission activities that want to contribute to the development in Wana, the results show that religious concept needs to be transformed through a contextual approach

DOSIS IRADIASI OPTIMUM PADA PENGAWETAN SIMPLISIA KULIT BATANG MAHKOTA DEWA (Phaleria macrocarpa (Scheff) Boerl.) SEBAGAI ANTIKANKER

Percobaan ini bertujuan untuk mendapatkan dosisradiasi yang optimum untuk pengawetan dan sekaligus tidak menyebabkan kerusakan pada senyawa anti kanker dalam simplisia kulit batang mahkota dewa. Simplisia kulit batang mahkota dewa diiradiasi dengan 60Co pada beberapa variasidosis 0; 5; 7,5 ; 10; 15; dan 20 kGy dengan laju dosis 10 kGy/jam. Simplisia yang telah diiradiasi dan kontrol masing-masing dimaserasi secara bertingkat menggunakan n-heksan dan etil asetat, kemudian ekstrak etil asetat difraksinasi baik yang diiradiasi maupun kontrol, dilanjutkan dengan fraksinasi terhadap ekstrak etil asetat menggunakan kolom kromatografi sehingga diperoleh masing-masing 8 fraksi. Uji cemaran mikroba terhadap simplisia kulit batang mahkota dewa yang telah diiradiasi dan kontrol menunjukkan bahwa iradiasi dosis ≥ 5 kGy pada simplisiadapat menghambat pertumbuhan serta membunuh semua bakteri, kapang dan khamir yang ada. Uji aktivitas sitotoksik terhadap ekstrak etil asetat dari simplisia yang telah diiradiasi menunjukkan bahwa iradiasi sampai dengan 20 kGy dapat menurunkan aktivitas sitotoksik, meskipun nilai IC50 masih di bawah 50 μg/ml, yangmerupakan nilai batas aktivitas sitotoksik suatu ekstrak. Demikian juga halnya pada uji aktivitas sitotoksik terhadap fraksi 6 yang merupakan fraksi paling aktif dalam simplisia kulit batang mahkota dewa menunjukkan bahwa iradiasi terhadap simplisia sampai dengan dosis 20 kGy menurunkan aktivitas sitotoksik fraksi 6, namun nilai IC50 tersebut masih di bawah 20 μg/ml, yang merupakan batas aktivitas sitotoksik suatu fraksi. Analisis senyawa 2,4’—dihidroksi—4 metoksi benzofenon—2—O—β—D—glukopiranosida menggunakan kromatografi cair kinerja tinggi (KCKT) dalam fraksi 6 dari sampel yang diiradiasi menunjukkan bahwa semua konsentrasi senyawa tersebut dalam sampel yang diiradiasi menurun secara signifikan dibandingkan kontrol. Penurunan konsentrasi senyawa 2,4’—dihidroksi—4 metoksi benzofenon—2—O—β—D—glukopiranosida tidak sebanding dengan penurunan nilai aktivitas sitotoksik dalam ekstrak etil asetat maupun dalam fraksi 6, karena itu senyawa tersebut tidakdapat digunakan sebagai marka efek irradiasi terhadap penurunan aktivitas sitotoksik simplisia kulit batang mahkota dewa. Iradiasi pada dosis 5 sampai dengan 7,5 kGy merupakan pilihan terbaik untuk menurunkan angka cemaran bakteri dan kapang/khamir pada simplisia kulit batang mahkota dewa tanpa menurunkanaktivitas sitotoksik. Dosis iradiasi sampai dengan 20 kGy masih dapat digunakan,karena sampai dengan dosis tersebut penurunan aktivitas sitotoksik belummelampaui batas suatu ekstrak dan fraksi dinyatakan tidak aktif

Strain-dependent exciton diffusion in transition metal dichalcogenides

Monolayers of transition metal dichalcogenides have a remarkable excitonic landscape with deeply bound bright and dark exciton states. Their properties are strongly affected by lattice distortions that can be created in a controlled way via strain. Here, we perform a joint theory-experiment study investigating exciton diffusion in strained tungsten disulfide (WS2) monolayers. We reveal a non-trivial and non-monotonic influence of strain. Lattice deformations give rise to different energy shifts for bright and dark excitons changing the excitonic landscape, the efficiency of intervalley scattering channels and the weight of single exciton species to the overall exciton diffusion. We predict a minimal diffusion coefficient in unstrained WS2 followed by a steep speed-up by a factor of 3 for tensile biaxial strain at about 0.6% strain - in excellent agreement with our experiments. The obtained microscopic insights on the impact of strain on exciton diffusion are applicable to a broad class of multi-valley 2D materials

Mapping of the dark exciton landscape in transition metal dichalcogenides

Transition metal dichalcogenides (TMDs) exhibit a remarkable exciton physics including bright and optically forbidden dark excitonic states. Here, we show how dark excitons can be experimentally revealed by probing the intraexcitonic 1s-2p transition. Distinguishing the optical response shortly after the excitation and after the exciton thermalization allows us to reveal the relative position of bright and dark excitons. We find both in theory and experiment a clear blueshift in the optical response demonstrating the transition of bright exciton populations into lower-lying dark excitonic states

Probing correlations in the exciton landscape of a moir\'e heterostructure

Excitons are two-particle correlated bound states that are formed due to Coulomb interaction between single-particle holes and electrons. In the solid-state, cooperative interactions with surrounding quasiparticles can strongly tailor the exciton properties and potentially even create new correlated states of matter. It is thus highly desirable to access such cooperative and correlated exciton behavior on a fundamental level. Here, we find that the ultrafast transfer of an exciton's hole across a type-II band-aligned moir\'e heterostructure leads to a surprising sub-200-fs upshift of the single-particle energy of the electron being photoemitted from the two-particle exciton state. While energy relaxation usually leads to an energetic downshift of the spectroscopic signature, we show that this unusual upshift is a clear fingerprint of the correlated interactions of the electron and hole parts of the exciton quasiparticle. In this way, time-resolved photoelectron spectroscopy is straightforwardly established as a powerful method to access exciton correlations and cooperative behavior in two-dimensional quantum materials. Our work highlights this new capability and motivates the future study of optically inaccessible correlated excitonic and electronic states in moir\'e heterostructures.Comment: 32 pages, 4 main figures, 5 supplemental figure

Formation of moir\ue9 interlayer excitons in space and time

Moir\ue9 superlattices in atomically thin van der Waals heterostructures hold great promise for extended control of electronic and valleytronic lifetimes1-7, the confinement of excitons in artificial moir\ue9 lattices8-13 and the formation of exotic quantum phases14-18. Such moir\ue9-induced emergent phenomena are particularly strong for interlayer excitons, where the hole and the electron are localized in different layers of the heterostructure19,20. To exploit the full potential of correlated moir\ue9 and exciton physics, a thorough understanding of the ultrafast interlayer exciton formation process and the real-space wavefunction confinement is indispensable. Here we show that femtosecond photoemission momentum microscopy provides quantitative access to these key properties of the moir\ue9 interlayer excitons. First, we elucidate that interlayer excitons are dominantly formed through femtosecond exciton-phonon scattering and subsequent charge transfer\ua0at the interlayer-hybridized Σ valleys. Second, we show that interlayer excitons exhibit a momentum fingerprint that is a direct hallmark of the superlattice moir\ue9 modification. Third, we reconstruct the wavefunction distribution of the electronic part of the exciton and compare the size with the real-space moir\ue9 superlattice. Our work provides direct access to interlayer exciton formation dynamics in space and time and reveals opportunities to study correlated moir\ue9 and exciton physics for the future realization of exotic quantum phases of matter

Ultrafast dynamics of bright and dark excitons in monolayer WSe2_2 and heterobilayer WSe2_2/MoS2_2

The energy landscape of optical excitations in mono- and few-layer transition metal dichalcogenides (TMDs) is dominated by optically bright and dark excitons. These excitons can be fully localized within a single TMD layer, or the electron- and the hole-component of the exciton can be charge-separated over multiple TMD layers. Such intra- or interlayer excitons have been characterized in detail using all-optical spectroscopies, and, more recently, photoemission spectroscopy. In addition, there are so-called hybrid excitons whose electron- and/or hole-component are delocalized over two or more TMD layers, and therefore provide a promising pathway to mediate charge-transfer processes across the TMD interface. Hence, an in-situ characterization of their energy landscape and dynamics is of vital interest. In this work, using femtosecond momentum microscopy combined with many-particle modeling, we quantitatively compare the dynamics of momentum-indirect intralayer excitons in monolayer WSe$_2$ with the dynamics of momentum-indirect hybrid excitons in heterobilayer WSe$_2$/MoS$_2$, and draw three key conclusions: First, we find that the energy of hybrid excitons is reduced when compared to excitons with pure intralayer character. Second, we show that the momentum-indirect intralayer and hybrid excitons are formed via exciton-phonon scattering from optically excited bright excitons. And third, we demonstrate that the efficiency for phonon absorption and emission processes in the mono- and the heterobilayer is strongly dependent on the energy alignment of the intralayer and hybrid excitons with respect to the optically excited bright exciton. Overall, our work provides microscopic insights into exciton dynamics in TMD mono- and bilayers.Comment: 27 pages, 5 figure

Ultrafast nano-imaging of dark excitons

The role and impact of spatial heterogeneity in two-dimensional quantum materials represents one of the major research quests regarding the future application of these materials in optoelectronics and quantum information science. In the case of transition-metal dichalcogenide heterostructures, in particular, direct access to heterogeneities in the dark-exciton landscape with nanometer spatial and ultrafast time resolution is highly desired, but remains largely elusive. Here, we introduce ultrafast dark field momentum microscopy to spatio-temporally resolve dark exciton formation dynamics in a twisted WSe$_2$/MoS$_2$ heterostructure with 55 femtosecond time- and 500~nm spatial resolution. This allows us to directly map spatial heterogeneity in the electronic and excitonic structure, and to correlate these with the dark exciton formation and relaxation dynamics. The benefits of simultaneous ultrafast nanoscale dark-field momentum microscopy and spectroscopy is groundbreaking for the present study, and opens the door to new types of experiments with unprecedented spectroscopic and spatiotemporal capabilities.Comment: 39 pages, 4 main figures, 8 supplemental figure

Inverted valley polarization in optically excited transition metal dichalcogenides

Large spin-orbit coupling in combination with circular dichroism allows access to spin-polarized and valley-polarized states in a controlled way in transition metal dichalcogenides. The promising application in spin-valleytronics devices requires a thorough understanding of intervalley coupling mechanisms, which determine the lifetime of spin and valley polarizations. Here we present a joint theory-experiment study shedding light on the Dexter-like intervalley coupling. We reveal that this mechanism couples A and B excitonic states in different valleys, giving rise to an efficient intervalley transfer of coherent exciton populations. We demonstrate that the valley polarization vanishes and is even inverted for A excitons, when the B exciton is resonantly excited and vice versa. Our theoretical findings are supported by energy-resolved and valley-resolved pump-probe experiments and also provide an explanation for the recently measured up-conversion in photoluminescence. The gained insights might help to develop strategies to overcome the intrinsic limit for spin and valley polarizations

Small Polarons in Transition Metal Oxides

The formation of polarons is a pervasive phenomenon in transition metal oxide compounds, with a strong impact on the physical properties and functionalities of the hosting materials. In its original formulation the polaron problem considers a single charge carrier in a polar crystal interacting with its surrounding lattice. Depending on the spatial extension of the polaron quasiparticle, originating from the coupling between the excess charge and the phonon field, one speaks of small or large polarons. This chapter discusses the modeling of small polarons in real materials, with a particular focus on the archetypal polaron material TiO2. After an introductory part, surveying the fundamental theoretical and experimental aspects of the physics of polarons, the chapter examines how to model small polarons using first principles schemes in order to predict, understand and interpret a variety of polaron properties in bulk phases and surfaces. Following the spirit of this handbook, different types of computational procedures and prescriptions are presented with specific instructions on the setup required to model polaron effects.Comment: 36 pages, 12 figure