1,380,131 research outputs found
Tantalum pentoxide waveguide amplifier and laser for planar lightwave circuits
No full textA planar lightwave circuit (PLC) has been envisioned to provide a new generation of optical networks capable of delivering signal at high speed and bandwidth to the household. High index contrast (HIC) and optical gain in the same material system would substantially enhance integration of different optical devices in a small area and compensate for the losses in the system to realise low cost, dense multi-functional PLCs. This thesis investigates the use of tantala as a HIC material system for realising gain efficient Erbium doped waveguide amplifiers (EDWAs) and lasers to be used at 1.5µm wavelength, towards realising dense multi-functional PLCs.Slab waveguides were fabricated by magnetron sputter deposition under optimised conditions of a powder pressed, Er:Ta2O5 target onto an oxidized silicon substrate. Optimised sputtering process yielded a Er:Ta2O5 thin film with a refractive index of 2.105 @ 1550 nm and a maximum erbium lifetime of 2.3 ms. Single mode rib waveguides were designed and the fabricated using photolithography and argon ion beam milling. A maximum propagation loss of 0.65 ± 0.05 dB/cm at 1600 nm was measured, the peak erbium absorption and emission cross-section was determined to be 4.8 ± 0.2 x 10-21 cm2 and 4.4 ± 0.2 x 10-21 cm2 respectively.Numerical modeling of Er:Ta2O5 based EDWA predicted a maximum gain of 4 dB/cm at 200 mW pump power, in a 5.4cm long waveguide with an erbium concentration of 5.4 x 1020 ions/cm3. Gain measurements were performed on a 2.3cm long rib waveguide with a erbium concentration of 2.7 x 1020 ions/cm3, at a pump power of 200mW, and a net optical gain of 2.25dB/cm peaking at 1531.5 nm was measured in a 2µm wide waveguide. The pump threshold with respect to the launched pump power was measured to be as low as 4.5mW. The cavity was formed by affixing two mirrors at the end facets of the waveguides. Lasing was observed in a single longitudinal and transverse mode peaking between 1556 and 1560nm. The lasing threshold of 14mW with a slope efficiency of 0.3% was measured with respect to the launched power.Finally, a feasibility study for inscribing sub-micron grating structures on the Er:Ta2O5 waveguides were carried out using interferometric ablation. Gratings inscribed with 23 mJ/cm2 energy density and 1000 pulses yielded a maximum reflectivity of 11dB for TE polarisation at 1505nm. This feasibility study shows potential to realise integrated cavity line narrowed lasers and filters. Tantala has long been used for different photonic applications but gain at 1.5 μm is demonstrated for the first time. The results presented in the thesis demonstrate that tantala due to its HIC, net optical gain and other inherent properties that it possesses have the potential to realise low cost, compact PLCs for the short haul networks
Sarah Subramanian Interview
No full textSarah Subramanian (Class of 2020) was interviewed by Valeria Reynosa via the Zoom internet-based video conferencing software on December 17, 2020. Ms. Subramanian was born in New Delhi, India, where she lived for most of her childhood. Her family relocated to the United States when she was twelve years old. She describes the differences in culture between India and the United States as she navigated middle school and high school life. She attended Rampart High School in Colorado Springs and discussed how the institution lacked racial diversity. After high school, she decided to attend SMU to prepare herself for a law career. She was involved in organizations like Not on My Campus, Mustang Heroes, Sigma Phi Lambda, and Feminist Equality Movement (FEM). Her most memorable experience was when she won an essay prize from SMU's Hyer Society, writing about gender inequality in law. Her family's support and working for the Meadows Museum allowed her to earn a bachelor's in Business Administration and a minor in Law and Legal Reasoning. After graduating, she decided to attend Texas A&M's Law School because recruiters and the administration welcomed her. At the time of the interview, she was a first-year law student navigating graduate studies during the COVID pandemic
The impact of Bt cotton on poor households in rural India
No full textThe impact of genetically modified (GM) crops on the poor in developing countries is still the subject of controversy. While previous studies have examined direct productivity effects of Bacillus thuringiensis (Bt) cotton and other GM crops, little is known about wider socioeconomic outcomes. We use a microeconomic modelling approach and comprehensive survey data from India to analyse welfare and distribution effects in a typical village economy. Bt cotton adoption increases returns to labour, especially for hired female workers. Likewise, aggregate household incomes rise, including for poor and vulnerable farmers. Hence, Bt cotton contributes to poverty reduction and rural development
Recommended from our members
Leysia Palen and Deepika Rama Subramanian: Fertile Ground: Women's Bodies as Sites for Motivating Disinformation
No full textThis presentation was made by Leysia Palen and Deepika Rama Subramanian. The presentation’s title is: “Fertile Ground: Women's Bodies as Sites for Motivating Disinformation.”
--
Every month, the COVID Information Commons Team (along with the Northeast Big Data Innovation Hub) brings together a group of researchers studying wide-ranging aspects of the current pandemic, to share their research and answer questions from our community. The events showcase scientists' ongoing efforts in the fight against COVID-19, including opportunities for collaboration
Stressed over dessert
No full textJournal #12 from Media Rise's Quarantined Across Borders Collection by Priya Subramanian. From India. Quarantined in Houston, TX.Media Rise Publications. Quarantined Across Borders Collection. Edited by Dr. Srividya "Srivi" Ramasubramanian.An everyday act of baking and sharing gets complicated during a pandemic
Social Groups and Economic Poverty: A Problem in Measurement
No full textThis paper points to some elementary conflicts between the claims of interpersonal and intergroup justice as they manifest themselves in the process of seeking a real-valued index of poverty which is required to satisfy certain seemingly desirable properties. It indicates how ?group-sensitive? poverty measures, similar to the Anand-Sen (1995) ?Gender Adjusted Human Development Index? and the Subramanian-Majumdar (2002) ?Group-Disparity Adjusted Deprivation Index?, may be constructed. Some properties of a specific ?group-sensitive? poverty index are appraised, and the advantage of having a ?flexible? measure which is capable of effecting a tradeoff between the claims of interpersonal and inter-group equality is spelt out. The implications of directly incorporating group disparities into the measurement of poverty for poverty comparisons and anti-poverty policy are also discussed.poverty, measurement, social groups, symmetry, transfer, subgroup sensitivity
Choroterpes (Choroterpes) kaegies Selvakumar & Subramanian & Chandra & Jehamalar 2017, sp. n.
No full text<i>Choroterpes</i> (<i>Choroterpes</i>) <i>kaegies</i> Selvakumar, Subramanian & Chandra sp. n. (Figs 1–16) <p> <b>Material examined.</b> Holotype: 1 larva, INDIA, Meghalaya, East Khasi Hills, Khrang village, Wankwar River, 25.32481 N, 91.77519 E, 1658 m, 02.iii.2016, coll. E. Eyarin Jehamalar (Reg. No. 5144). Paratypes: 5 larvae, same data as holotype; 2 larvae, Meghalaya, East Khasi Hills, Thangasalai village, Umkhen River, 25.59186 N, 92.05494 E, 937 m, 05.iii.2016, coll. E. Eyarin Jehamalar (Reg. No. 5147/H13); 1 larva, Meghalaya, East Garo Hills, Upper Rongbu village, 25.91615 N, 90.83157 E, 101 m, 26.vi.2016, coll. E. Eyarin Jehamalar (Reg. No. 5149/H13); 1 larva, Himachal Pradesh, Bilaspur district, Mandodari, River stream, 31.783 N, 76.332 E, 18.xi.2012, coll. K.A. Subramanian.</p> <p> <b>Description.</b> Body length 4.6–5.0 mm (Fig. 1). Antennae approximately 3.0 mm. Head prognathous, light yellowbrown with diffuse black markings. Labrum with 3 transverse, near parallel, rows of setae on dorsal surface, both distal and proximal transverse setal rows regular; anteromedian emargination broad (Fig. 2). Lingua of hypopharynx with well developed lateral process, anterior margin cleft (Fig. 3). Lateral margins of mandibles with scattered setae, inner mandibular incisor slightly longer than outer one (Figs 4–5). Maxillary palp 3 segmented; segment 2 subequal in length to segment 1, segment 3 approximately ¾ length of segment 2 (Fig. 6). Labium: glossa with thick plate-like setae on ventral surface, fewer setae on dorsal surface; paraglossa with denser but fewer setae on dorsal surface; first segment of palp with thick setae on margins, second segment with setae on outer margin, apical segment with thick and fine setae on margin and surface, those near apex of apical segment gathered into small tufts; segment 1 length subequal to segment 2 length, segment 3 length 0.7 times segment 2 length (Fig. 7).</p> <p>Pronotum light yellow-brown with diffuse black markings medially. Meso- and metanota yellow-brown tinged with dark brown or black laterally. Legs pale; each femur with a dark brown spot at middle and near apex; femora with thick and thin setae on outer margin; tibiae with fine and thick setae on inner margin, and very sparse and thin setae on inner margin, and very sparse and thin setae on outer margin, but hind tibiae mixed with more denser thick and few feathered setae on surface; tarsi of all legs with several thin setae on inner margin and sparse setae on outer margins (Figs 8–10). Claw apically hooked with a row of 4–5 denticles, progressively larger apically (Fig. 11).</p> <p>Abdominal terga 1–10 light yellow-brown with diffuse black markings; terga 1–10 with posterior marginal spines; posterolateral margins of abdominal terga with pointed denticles, size of denticles increases from tergum 6 to tergum 9. Gills on segments 1–7; gill 1 single, slender, lanceolate (Fig. 12); gills 2–7 alike, well-tracheated, upper and lower lamellae of gills 2–7 with 3 apical processes, median process relatively long and other relatively short (Figs 13–16). Sternum 9 of male with deep apical cleft, sternum 9 of female with apex entire and without emargination. Caudal filaments pale yellow-brown; with a whorl of setae on alternate segments; setae shorter than length of corresponding segment.</p> <p> <b>Adult.</b> Unknown.</p> <p> <b>Etymology.</b> The species name “ <i>kaegies</i> ” (pronounced as KGS) is abbreviated patronym of Prof. K.G. Sivaramakrishnan who has significantly contributed to Ephemeroptera taxonomy in India. He is popularly known among his peers, friends and students as “KGS” and hence the species name.</p> <p> <b>Distribution.</b> India (Meghalaya and Himachal Pradesh).</p> <p> <b>Diagnosis.</b> <i>Choroterpes</i> (<i>C.</i>) <i>kaegies</i> Selvakumar, Subramanian & Chandra <b>sp. n.</b> can be distinguished from all known species of <i>Choroterpes</i> (<i>C.</i>) by the following characters: (i) anteromedian emargination of labrum broad (Fig. 2); (ii) each femur with a dark brown spot at middle and near apex (Figs 8–10); (iii) gill 1 single and slender (Fig. 12) and (iv) upper and lower lamellae of gills 2–7 with 3 apical processes, median process relatively slender and longer than laterals (Figs 13–16).</p> <p> <b>Discussion.</b> In India, only two species are recorded from the subgenus <i>Choroterpes</i> s. str. <i>viz</i>., <i>Choroterpes</i> (<i>C.</i>) <i>petersi</i> Tong and Dudgeon, 2003 from southern Western Ghats by Selvakumar <i>et al.</i> (2015) which was originally described from Hong Kong and the present new species, <i>Choroterpes</i> (<i>C.</i>) <i>kaegies</i> Selvakumar, Subramanian & Chandra <b>sp. n.</b> from Himachal Pradesh and Meghalaya. The distribution of <i>Choroterpes</i> (<i>C.</i>) <i>petersi</i> Tong and Dudgeon, 2003 appears to be disjunct in its geographical range. However, <i>Choroterpes</i> (<i>C.</i>) <i>kaegies</i> Selvakumar, Subramanian & Chandra <b>sp. n.</b> is probably widely distributed in Himalaya as the collection localities from two states are geographically widely separated. However, detailed surveys are required. In future detailed morphosystematics and molecular phylogenetic studies are required to fine-tune the subgeneric relationships within the genus <i>Choroterpes</i> Eaton, 1881.</p>Published as part of <i>Selvakumar, C., Subramanian, K. A., Chandra, Kailash & Jehamalar, E. Eyarin, 2017, A new species of Choroterpes Eaton, 1881 (Ephemeroptera: Leptophlebiidae) from India, pp. 189-194 in Zootaxa 4338 (1)</i> on pages 190-193, DOI: 10.11646/zootaxa.4338.1.12, <a href="http://zenodo.org/record/1035542">http://zenodo.org/record/1035542</a>
An iterated local search algorithm for the Travelling Salesman Problem with Pickups and Deliveries
No full textThe Travelling Salesman Problem with Pickups and Deliveries (TSPPD) consists in designing a minimum cost tour that starts at the depot, provides either a pickup or delivery service to each of the customers and returns to the depot, in such a way that the vehicle capacity is not exceeded in any part of the tour. In this paper, the TSPPD is solved by considering a metaheuristic algorithm based on Iterated Local Search with Variable Neighbourhood Descent and Random neighbourhood ordering. Our aim is to propose a fast, flexible and easy to code algorithm, also capable of producing high quality solutions. The results of our computational experience show that the algorithm finds or improves the best known results reported in the literature within reasonable computational time
Notacanthurus pange Vasanth, Selvakumar & Subramanian 2020, sp. nov.
No full textNotacanthurus pange Vasanth, Selvakumar & Subramanian sp. nov. (Figs 1–19) Material examined. Holotype: Ƌ larva, INDIA, Arunachal Pradesh, Lower Subansiri district, Talley Valley Wildlife Sanctuary, Pange, 27.5485 N, 93.89756 E, 1851 m, 18.vi.2017, colls. K. A. Subramanian & M. Vasanth (I/E- 440). Paratypes: 2 larvae, same data as holotype (I/E-441); 4 larvae, Arunachal Pradesh, Lower Subansiri district, Duskilo river, 27.62776 N, 93.8437 E, 1662 m, 16.vi.2017, colls. K. A. Subramanian & M. Vasanth (I/E-442); 3 larvae, Arunachal Pradesh, Dibang Valley, Talo river near Apai village, 28.10402 N, 96.10402 E, 1323 m, 29.x.2017, coll. K. A. Subramanian (I/E-443); 2 larvae, Sikkim, East Sikkim, Stream near Nathu La, 27.36718 N; 88.8400 E, 3856 m, 18.ix.2018, coll. K. A. Subramanian (I/E-444); 4 larvae, Meghalaya, East Jaintia hills, Daidung village, 25.33547 N, 92.61981 E, 1079 m, 12.iii.2016, coll. E. Eyarin Jehamalar. Description. Mature male larva: Body length 7.8 mm, length of caudal filaments 8.6 mm (Figs 1–2). Head: Head subquadrate, brown, with irregular pale yellow markings (Figs 1–2); anterior and lateral margins round; posterior margin concave; head width 3.4 mm, head length 1.3 mm; eyes black, antennae pale brown. Labrum with anterior portion straight and laterally curved; dorsally with dense hair-like setae (Fig. 4). Mandibles with scattered setae along molar area; incisor well developed; dense hair-like setae on anterolateral margin (Figs 6–7). Maxillae with 19–20 comb-like setae on crown, with scattered hair-like setae on ventral surface; outer margin of maxillary palp segment 2 and 3 with long hair-like setal field; terminal segment of maxillary palp with dense hairlike setae (Fig. 8). Hypopharynx: lingua apically broad and convex; superlinguae each with lateral arm developed, with dense row of hair-like setae (Fig. 5). Labium with wide U-shaped division of glossae; glossae subquadrangular; paraglossae expanded laterally; apical segment of each labial palp acutely pointed, dorsal surface with dense row of setae (Fig. 9). Thorax: Thorax brown with scattered brown markings around basal wing pads; pronotum extended laterally, a little wider than head (Fig 1–2), pronotum width 3.4 mm. Legs: Forefemora pale brown, with median pale yellowish maculae, scattered short simple stout setae on dorsal surfaces, apex of femora with blunt apical projection, with row of long setae on outer margin; fore tibiae subequal to femora in length, outer margin with few tiny and short setae at base, foretarsi 1/3 length of foretibiae (Figs 10–11). Mid and hind legs (Figs 12–13) similar to forelegs in color and setation; mid tibiae with dense setae on outer margin, tarsi 1/3 length of tibiae and hind tibiae with dense hair-like setae along the whole outer margin. Claws of all legs similar, with a large basal denticle and 2 subapical denticles (Fig. 14). Abdomen: Terga brown, with distinct oblique markings; terga I–IX each with single prominent median spine (Fig 1–2), with row of short bristles on posterior margin (Fig. 3). Sterna pale white; posterior end of sternum X with notched (Fig. 19). Gills on segment I–VII; Gills with both lamellae and fibrilliform portion on abdominal segments I–VI (Figs 15–18); gill VII with only lamellae; lamellae of gills I knife-shaped (Fig. 15); gills II–VI each with oval shape anteriorly; gills V–VI each with accessory lobe (Figs 17–18); gill VII narrower lanceolate, with fine hair-like marginal setae. Genitals: Protopenis (Fig. 19) male genitalia with simple, penis lobes fused, V shaped apically blunt with median pair of spine-like titillators subapically and mesally. Cerci about 1.2x length of body, each segment with whorls of minute bristles and without interfacing setae. Diagnosis: Notacanthurus pange sp. nov. can be distinguished from all known species of Notacanthurus by the following combination of characters: (i) gill lamellae V–VI with accessory lobe (Figs. 17–18); (ii) dorsal surface of femora with scattered short simple stout setae (Fig. 11); (iii) male genitalia having penis lobes fused, V shaped apically blunt with median pair of spine-like titillators subapically and mesally (Fig. 19); (iv) labrum with anterior portion straight and laterally curved (Fig. 4); and (v) lingua of hypopharynx apically broad and convex (Fig. 5). Notacanthurus pange sp. nov. can be accommodated in the recent global larval key to the species of Notacanthurus by Zhang et al. (2020). The second part of the 5 th couplet of that key can be modified and a new couplet should be added to include Notacanthurus pange sp. nov. as follows: 5. Abdominal terga with oblique stripes...................................................................... 7 - Abdominal terga without distinct markings................................................................. 6 6. Dorsal surface of femora with apically blunt scattered stout setae.................................. N. pange sp. nov. - Dorsal surface of femora with apically pointed stout setae.............................................. N. baekdu Imagos: Unknown. Etymology: The species named after the type locality, Pange, Lower Subansiri district, Arunachal Pradesh state, India. Habitat: The specimens were collected among cobbles from cold pristine hill streams between 1100-3860m. The riparian habitat ranged from subtropical broad leaved evergreen forests (Arunachal Pradesh and Meghalaya) to alpine meadows (Sikkim) (Fig. 20). Distribution: India (Arunachal Pradesh, Meghalaya and Sikkim) (Fig. 21).Published as part of Vasanth, M., Selvakumar, C., Subramanian, K. A., Sivaramakrishnan, K. G. & Sinha, Bikramjit, 2020, A new species of Notacanthurus Tshernova, 1974 (Ephemeroptera: Heptageniidae) from India, pp. 437-444 in Zootaxa 4894 (3) on pages 438-442, DOI: 10.11646/zootaxa.4894.3.9, http://zenodo.org/record/431597
- …
