IPA Recipients for October 2019

Karlo de leon1, Michael Francis Ian G. Vega II1
1National Institute of Physics, College of Science (UP Diliman)

Weak Gravitational Deflection by Two-power-law Densities Using the Gauss-Bonnet Theorem, Physical Review D, 99 (12): 124007, 2019

Light rays bend around galaxies. In general relativity, the presence of mass curves spacetime, and this curvature bends light. Every galaxy then, depending on how mass is arranged inside it, has its own signature on how it deflects light. This allows us to “see” how mass may be distributed in a galaxy just by looking at how it deflects light around it. Knowing this is important in astrophysics, answering bigger questions like how much of the universe is dark matter, how galaxies form, etc.

Our work focuses on how a specific class of low-density galaxies deflects light. We worked with the so-called two-power-law densities, where the spherical mass distribution follows a power-law near the center of the galaxy and another different power-law at its far edges. The model is often used in astrophysics to approximate the densities of elliptical galaxies with small eccentricity, and in modeling hypothesized dark matter halos that accompany the visible content of many galaxies. Aside from insights on the mass distributions, knowing the deflection behavior is fundamental in understanding the more complicated optical properties of galaxies that act as lenses.

We all know light bends when it travels across different media: from water to air, making the fishes look closer to the surface, or from glass to air like in eyeglasses, correcting a blurry scientific paper to a crisp and clear image of scientific jargons. There is, however, another totally different way of bending light—through gravity. Just like how mass attracts other mass by gravity, the light also responds to the presence of mass. The effect may be negligible when it comes to everyday objects, but for very very heavy objects like the Sun and galaxies, the phenomenon is observable. A galaxy, in fact, has a unique signature on how it bends light. This is determined by how mass is distributed in it. In this study, we focused on a set of galaxies called the two-power-law-density galaxies and predicted how they are supposed to bend light using Einstein’s general relativity. Astrophysicists can use our results to infer how stars in some galaxies might be arranged by looking at how these galaxies deflect light around them.

Link to the article: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.99.124007
Impact factor: (2018/2019) 4.368

Valerie Shayne V. Olfindo1, Betchaida D. Payot1, Carla B. Dimalanta1
1National Institute of Geological Sciences, College of Science (UP Diliman)

Petrographic and Geochemical Characterization of the Crustal Section of the Pujada Ophiolite, Southeastern Mindanao, Philippines: Insights to the Tectonic Evolution of the Northern Molucca Sea Collision Complex, Journal of Asian Earth Sciences, 184: 103994, doi: 10.1016/j.jseaes.2019.103994, 2019

Gabbros comprising the crustal section of the Pujada Ophiolite in hand sample (left) and as seen under the petrographic microscope (right). The gabbros are composed of interlocking grains of olivine (ol), plagioclase (plg), clinopyroxene (cpx) and orthopyroxene (opx).

Representative cathodoluminescence images of zircons from gabbros of the Pujada Ophiolite with their corresponding ages obtained using U-Pb dating (top). Secondary electron image (SEI) of zircons during laser ablation (bottom).

An ophiolite is a sequence of rocks representative of ancient oceanic crust and upper mantle which has been uplifted above sea level and emplaced onland. Ophiolites are important because they provide Earth scientists the opportunity to directly study rocks that are otherwise covered by seawater. Several ophiolites comprise the basement of the Philippine archipelago. The Pujada Ophiolite is a complete ophiolite sequence located at the southeasternmost tip of Mindanao where the interactions between the Eurasian, Philippine Sea and the completely subducted Molucca Sea Plates (Molucca Sea Collision Complex) are recorded. Our work reveals that the Pujada Ophiolite is an onland representation of a trapped fragment of the proto-Molucca Sea Plate which was thrusted onto the Molucca Sea Collision Zone. Uranium-lead (U-Pb) dating of zircons from the isotropic gabbros further constrains the age of the Pujada Ophiolite to Late Cretaceous (90 Ma). This age is consistent with the inferred age of the proto-Molucca Sea Plate based on tectonic reconstructions and tomography.

This research explores the petrological characteristics of the crustal units of the Pujada Ophiolite in southeast Mindanao, Philippines. In this work, we were also able to constrain the age of the Pujada Ophiolite to Late Cretaceous (90 Ma). These petrological imprints provide evidence for magmatic and tectonic processes that help in deciphering how the southeasternmost portion of Mindanao evolved for the past million years to its present-day configuration.

Link to the article: https://www.sciencedirect.com/science/article/pii/S1367912019303463
Impact factor: (2018/2019) 2.762

Lean L. Dasallas1, Wilson O. Garcia1, Roland V. Sarmago1
1National Institute of Physics, College of Science (UP Diliman)

Synthesis of Iron Oxide Nanostructures via Carbothermal Reactions of Fe Microspheres Generated by Infrared Pulsed Laser Ablation, Coatings, 9(3):179, 2019

Using the laser beam to vaporize the surface of the material has long been used in many science fiction stories such as laser guns and laser swords. In reality, these kinds of a laser can take many forms, such as semiconductor laser and gas-based laser. The latter type of laser has been generally used to vaporize the surface of many solid materials such as metals, insulators, and many more. However, gas-based laser (in particular, excimer laser) are usually difficult to handle since the gases are toxic. Aside from that, the excimer laser is usually costly to operate since one needs to replenish the excimer gas from time to time to maintain operation. In our research, we used an alternative laser (solid-state Nd:YAG laser) to vaporize the surface of a material (Iron Oxide) and determined the resulting properties. The Iron oxide in thin-film form was subjected to carbothermal heat treatment in order to produce nanostructures with interesting properties. Because of this result, we are able to show that an alternative type of laser can be used instead of the popular type.

Producing nanomaterial offers a new way of designing functional devices for different technological applications. One way to produce nanomaterials in thin-film form is through pulsed laser deposition. In general, the laser choice for pulsed laser deposition is gas-based lasers operating in the ultraviolet wavelength (UV) range. However, there are some disadvantages in the used of excimer (gas) laser, including (1) cost of the gas sources (2) the apparent deviation of the composition of the grown layer, which has a complex stoichiometry (more than three elements), and (3) health risk due to possible inhalation of dangerous gas. Because of this, the use of an alternative laser source for PLD assisted growth is needed. In the research work, the use of solid-state laser for deposition of Iron Oxide nanostructures has been demonstrated.

Link to the article: https://www.mdpi.com/2079-6412/9/3/179
Impact factor: (2018/2019) 2.330

Julius A. Pasco1, Jesley Mei A. Dyoco1, Betchaida D. Payot1, Leo T. Armada1, Carla B. Dimalanta1
1National Institute of Geological Sciences, College of Science (UP Diliman)

Petrogenesis of ultramafic-mafic clasts in the Dos Hermanos Mélange, Ilocos Norte: Insights to the evolution of western Luzon, Philippines, Journal of Asian Earth Sciences, 184, https://doi.org/10.1016/j.jseaes.2019.104004, 2019

Exposure of the Dos Hermanos Mélange in Pasuquin, Ilocos Norte showing phacoid-shaped peridotite clasts within a sheared serpentinite matrix.

(a) Cross-polarized photomicrograph of a peridotite clast of the Dos Hermanos Mélange. (b) Backscattered electron image of the troctolite clast of the Dos Hermanos Mélange

A mélange is a chaotic mixture of a large block of various lithologies contained in a fine-grained deformed matrix. Mélange occurrences are often associated with major fault-related events. This work focuses on the Dos Hermanos Mélange (DHM) in Ilocos Norte, Luzon. The DHM is composed of peridotites, gabbros, cherts and metamorphic rocks chaotically mixed within a highly deformed matrix. Petrographic and geochemical characteristics of the rocks in the DHM suggest that they were formed both in a spreading center, and a volcanic island arc. These signatures are also similar to the rocks in the Zambales Ophiolite Complex. The Dos Hermanos Mélange and the Zambales Ophiolite Complex were possibly derived from the same fossil oceanic lithosphere. Strike-slip faulting in the region led to the unique field characteristics of the Dos Hermanos Mélange.

This work presents the first petrological and geochemical investigation of the Dos Hermanos Mélange (DHM) in Ilocos Norte, Luzon. Novel petrographic and geochemical characteristics reveal that the rocks comprising the DHM are similar to the ophiolitic rocks of the Zambales Ophiolite Complex (ZOC). Through this work, we were able to establish that the DHM and the ZOC were derived from the same oceanic lithosphere. Strike-slip faulting may have transpired in the region, leading to the present-day configuration of the DHM.

Link to the article: https://www.sciencedirect.com/science/article/pii/S1367912019303566
Impact factor: (2018/2019) 2.762