A new exact quantum mechanical propagator

The authors derive a closed-form expression for the time-dependent propagator for a quantum mechanical particle which is subject to an external force which is the sum of (i) a reflecting half-plane barrier with a straight edge, and (ii) a harmonic force pointing towards a point of the edge. This new addition to the short list of exactly known quantum mechanical Green functions is a simple combination of exponential functions and Fresnel integrals, the arguments of which are combinations of trigonometric function

The history of the rice gene pool in Suriname: circulations of rice and people from the eighteenth century until late twentieth century

Alongside the trans-Atlantic slave trade, plant species travelled from Africa to the Americas and back. This article examines the emerging rice gene pool in Suriname due to the global circulation of people, plants and goods. We distinguish three phases of circulation, marked by two major transitions. Rice was brought to the Americas by European colonizers, mostly as food on board slave ships. In Suriname rice started off as a crop grown only by Maroon communities in the forests of the Suriname interior. For these runaway slaves cultivating several types of rice for diverse purposes played an important role in restoring some of their African culture. Rice was an anti-commodity that acted as a signal of protest against the slave-based plantation economy. After the end of slavery, contract labourers recruited from British India and the Dutch Indies also brought rice to Suriname. These groups grew rice as a commodity for internal and global markets. This formed the basis of a second transition, turning rice into an object of scientific research. The last phase of science-driven circulation of rice connected the late-colonial period with the global Green Revolution.El comercio transatlantico de esclavos tuvo como consecuencia la transferencia de numerosas especies vegetales. Este artículo se centra en la aparición de un acervo genético del arroz en Surinam, como consecuencia del tráfico de personas, plantas y mercancías. Hemos dividido la historia de la circulación global del arroz en tres etapas, separadas por dos etapas transicionales. El arroz llegó a América de la mano de los colonizadores, que lo empleaban como alimento, especialmente a bordo de los navíos que transportaban los esclavos. En Surinam no existían plantaciones de arroz, pero este cultivo pronto fue adoptado por grupos cimarrones formados por esclavos huidos hacia los bosques del interior de Surinam. El arroz parece haber jugado un papel fundamental para estos grupos, al permitirles restablecer algunos aspectos de su cultura africana ancestral, incluyendo el cultivo de distintas variedades de arroz. Como un símbolo de protesta contra las plantaciones con esclavos, el arroz cimarrón fue una antimercancía. Con el fin de la esclavitud llegaron a Surinam nuevos colectivos de trabajadores reclutados en las Indias británicas y holandesas. Estos grupos cultivaron arroz como una mercancía de primer orden. El artículo describe esta segunda transición, que convirtió este cereal en un objeto para la ciencia. Esta circulación de orientación científica conecta el período final colonial con la Revolución Verd

FAKTOR-FAKTOR YANG BERHUBUNGAN DENGAN PENGAMBILAN KEPUTUSAN MEMILIH PENOLONG PERSALINAN PADA IBU HAMIL DI WILAYAH KERJA PUSKESMAS LHOKNGA ACEH BESAR

Derajat kesehatan ibu dapat dinilai salah satunya dengan angka kematian ibu. Angka kematian ibu adalah kematian wanita yang terjadi selama masa kehamilan sampai dengan 42 hari setelah berakhirnya kehamilan. Angka kematian ibu bisa dipicu oleh penanganan persalinan yang dilakukan oleh penolong persalinan. Oleh sebab itu, ibu hamil harus memilih penolong persalinan yang tepat demi mencegah kematian ibu. Tujuan penelitian ini adalah mengetahui faktor-faktor yang berhubungan dengan pengambilan keputusan memilih penolong persalinan pada ibu hamil di wilayah kerja Puskesmas Lhoknga Aceh Besar tahun 2014. Jenis penelitian deskriptif korelatif dengan desain cross sectional study. Jumlah populasi 367 orang, pengambilan sampel dengan metode stratified random sampling pada 86 orang responden. Pengumpulan data dilakukan pada tanggal 3 Februari 2014 dengan menggunakan kuesioner berupa 51 pernyataan dalam bentuk dikotomi dan check list. Metode analisis data menggunakan uji Chi-Square. Hasil penelitian: tidak ada hubungan antara sosial budaya dengan pengambilan keputusan memilih penolong persalinan di wilayah kerja Puskesmas Lhoknga Aceh Besar tahun 2014 (p-value 0,437), pengetahuan (p-value 1,000), dukungan keluarga (p-value 0,699) dan fasilitas pelayanan kesehatan (p-value 0,236), namun ada hubungan sikap dengan pengambilan keputusan memilih penolong persalinan (p-value 0,055). Disarankan kepada ibu hamil agar dapat mencari informasi mengenai persalinan sehingga dapat memilih tindakan tepat terkait persalinan agar keselamatan serta kesehatan ibu dan bayi terjamin.Banda Ace

Spatial heterogeneity and irreversible vegetation change in semi-arid grazing systems

Recent theoretical studies have shown that spatial redistribution of surface water may explain the occurrence of patterns of alternating vegetated and degraded patches in semiarid grasslands. These results implied, however, that spatial redistribution processes cannot explain the collapse of production on coarser scales observed in these systems. We present a spatially explicit vegetation model to investigate possible mechanisms explaining irreversible vegetation collapse on coarse spatial scales. The model results indicate that the dynamics of vegetation on coarse scales are determined by the interaction of two spatial feedback processes. Loss of plant cover in a certain area results in increased availability of water in remaining vegetated patches through run-on of surface water, promoting within-patch plant production. Hence, spatial redistribution of surface water creates negative feedback between reduced plant cover and increased plant growth in remaining vegetation. Reduced plant cover, however, results in focusing of herbivore grazing in the remaining vegetation. Hence, redistribution of herbivores creates positive feedback between reduced plant cover and increased losses due to grazing in remaining vegetated patches, leading to collapse of the entire vegetation. This may explain irreversible vegetation shifts in semiarid grasslands on coarse spatial scales

Ethnobotany of Wild and Semi-Wild Edible Fruit Species used by Maale and Ari Ethnic Communities in Southern Ethiopia

Wild and semi-wild tree fruit species are important resources in combating food insecurity and providing supplementary diet to rural people. We studied wild and semi-wild fruit species used by the Maale and Ari communities in southern Ethiopia and the conservation status of these resources. We used focus group discussions (n = 18) and individual interviews (n = 144) in three rural kebeles. In total, the two communities used 52 species of wild and semi-wild fruit species which were especially important for their diet in times of food shortage. The most important species were, for the Maale community, Balanites rotundifolia (Tiegh.) Blatt. and Dobera glabra (Forssk.) Juss. ex Poir. and, for the Ari community, Carissa spinarum L. and Vitex doniana Sweet. No significant variation in ethnobotanical knowledge regarding fruit species existed among gender and age groups. The main traded fruit species were B. rotundifolia, Ximenia caffra Sond., and Vangueria madagascariensis J.F.Gmel. The major threats reported by informants to the availability of wild and semi-wild fruit species were tree felling and conversion of forest to agricultural land. In addition to preserving the local knowledge and implementing conservation strategies that protect the remaining fruit trees, maintenance and enrichment planting of the most important species are plausible management interventions

Assessment of Chimpanzee Nests Detectability on Drone-Acquired Images

As with other species of great apes, chimpanzee numbers have declined during the past decades. Proper conservation of the remaining chimpanzees requires accurate and frequent data on their distribution and density. In Tanzania, 75% of the chimpanzees live at low densities on land outside national parks and little is known about their distribution, density, behavior or ecology. Given the sheer scale of chimpanzee distribution across western Tanzania (>20,000 km2), we need new methods that are time and cost efficient while providing precise and accurate data across broad spatial scales. Scientists have recently demonstrated the usefulness of drones to detect wildlife, including apes. Whilst direct observation of chimpanzees is unlikely given their elusiveness, we investigated the potential of drones to detect chimpanzee nests in the Issa valley, western Tanzania. Between 2015 and 2016, we tested and compared the capabilities of two fixed-wing drones. We surveyed twenty-two plots (50x500m) in gallery forests and miombo woodlands to compare nest observations from the ground with those from the air. We performed mixed-effects logistic regression models to evaluate the impact of image resolution, seasonality, vegetation type, nest height and color on nest detectability. An average of 10% of the nests spotted from the ground were detected from the air. From the factors tested, only image resolution significantly influenced nest detectability on drone-acquired images. We discuss the potential, but also the limitations of this technology for determining chimpanzee distribution and density and provide guidance for future investigation on the use of drones for ape population surveys. Combining traditional and novel technological methods of surveying allows more accurate collection on animal distribution and habitat connectivity that has important implications for apes conservation in an increasingly anthropogenically disturbed landscape