Displaying publications 21 - 40 of 63 in total

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  1. Fulltext Demographic History and Genetic Adaptation in the Himalayan Region Inferred from Genome-Wide SNP Genotypes of 49 Populations
    Arciero E, Kraaijenbrink T, Asan, Haber M, Mezzavilla M, Ayub Q, et al.
    Mol Biol Evol, 2018 Aug 01;35(8):1916-1933.
    PMID: 29796643 DOI: 10.1093/molbev/msy094
    We genotyped 738 individuals belonging to 49 populations from Nepal, Bhutan, North India, or Tibet at over 500,000 SNPs, and analyzed the genotypes in the context of available worldwide population data in order to investigate the demographic history of the region and the genetic adaptations to the harsh environment. The Himalayan populations resembled other South and East Asians, but in addition displayed their own specific ancestral component and showed strong population structure and genetic drift. We also found evidence for multiple admixture events involving Himalayan populations and South/East Asians between 200 and 2,000 years ago. In comparisons with available ancient genomes, the Himalayans, like other East and South Asian populations, showed similar genetic affinity to Eurasian hunter-gatherers (a 24,000-year-old Upper Palaeolithic Siberian), and the related Bronze Age Yamnaya. The high-altitude Himalayan populations all shared a specific ancestral component, suggesting that genetic adaptation to life at high altitude originated only once in this region and subsequently spread. Combining four approaches to identifying specific positively selected loci, we confirmed that the strongest signals of high-altitude adaptation were located near the Endothelial PAS domain-containing protein 1 and Egl-9 Family Hypoxia Inducible Factor 1 loci, and discovered eight additional robust signals of high-altitude adaptation, five of which have strong biological functional links to such adaptation. In conclusion, the demographic history of Himalayan populations is complex, with strong local differentiation, reflecting both genetic and cultural factors; these populations also display evidence of multiple genetic adaptations to high-altitude environments.
    Matched MeSH terms: Altitude*
  2. Absolute Photoabsorption Cross-Sections of Methanol for Terrestrial and Astrophysical Relevance
    Lange E, Lozano AI, Jones NC, Hoffmann SV, Kumar S, Śmiałek MA, et al.
    J Phys Chem A, 2020 Sep 30.
    PMID: 32941031 DOI: 10.1021/acs.jpca.0c06615
    We investigate the methanol absorption spectrum in the range 5.5-10.8 eV to provide accurate and absolute cross-sections values. The main goal of this study is to provide a comprehensive analysis of methanol electronic-state spectroscopy by employing high-resolution vacuum ultraviolet (VUV) photoabsorption measurements together with state-of-the-art quantum chemical calculation methods. The VUV spectrum reveals several new features that are not previously reported in literature, for n > 3 in the transitions (nsσ(a') ← (2a″)) (1A' ← X̃1A') and (nsσ, npσ, npσ', ndσ ← (7a')) (1A' ← X̃1A'), and with particular relevance to vibrational progressions of the CH3 rocking mode, v11'(a″), mode in the (3pπ(a″) ← (2a″)) (21A' ← X̃1A') absorption band at 8.318 eV. The measured absolute photoabsorption cross-sections have subsequently been used to calculate the photolysis lifetime of methanol in the Earth's atmosphere from the ground level up to the limit of the stratosphere (50 km altitude). This shows that solar photolysis plays a negligible role in the removal of methanol from the lower atmosphere compared with competing sink mechanisms. Torsional potential energy scans, as a function of the internal rotation angle for the ground and first Rydberg states, have also been calculated as part of this investigation.
    Matched MeSH terms: Altitude
  3. Fulltext Low-Slow-Small (LSS) Target Detection Based on Micro Doppler Analysis in Forward Scattering Radar Geometry
    Musa SA, Raja Abdullah RSA, Sali A, Ismail A, Rashid NEA
    Sensors (Basel), 2019 Jul 29;19(15).
    PMID: 31362452 DOI: 10.3390/s19153332
    The increase in drone misuse by civilian apart from military applications is alarming and need to be addressed. This drone is characterized as a low altitude, slow speed, and small radar cross-section (RCS) (LSS) target and is considered difficult to be detected and classified among other biological targets, such as insects and birds existing in the same surveillance volume. Although several attempts reported the successful drone detection on radio frequency-based (RF), thermal, acoustic, video imaging, and other non-technical methods, however, there are also many limitations. Thus, this paper investigated a micro-Doppler analysis from drone rotating blades for detection in a special Forward Scattering Radar (FSR) geometry. The paper leveraged the identified benefits of FSR mode over conventional radars, such as improved radar cross-section (RCS) value irrespective of radar absorbing material (RAM), direct signal perturbation, and high resolutions. To prove the concept, a received signal model for micro-Doppler analysis, a simulation work, and experimental validation are elaborated and explained in the paper. Two rotating blades aspect angle scenarios were considered, which are (i) when drone makes a turn, the blade cross-sectional area faces the receiver and (ii) when drone maneuvers normally, the cross-sectional blade faces up. The FSR system successfully detected a commercial drone and extracted the micro features of a rotating blade. It further verified the feasibility of using a parabolic dish antenna as a receiver in FSR geometry; this marked an appreciable achievement towards the FSR system performance, which in future could be implemented as either active or passive FSR system.
    Matched MeSH terms: Altitude
  4. Fulltext CropCam UAV for land use/land cover mapping over Penang Island, Malaysia
    Faez M. Hassan, Lim, H.S., Mat Jafri, M.Z.
    Pertanika Journal of Science & Technology, 2011;19(3):69-76.
    MyJurnal
    The problem of difficulty in obtaining cloud-free scene at the equatorial region from satellite platforms can be
    overcome by using airborne imagery as an attempt for introducing an economical method of remote sensing
    data; which only requires a digital camera to provide near time data. Forty three digital images were captured
    using a high resolution digital camera model pentax optio A40 (12 megapixels)at a selected location in the same day in Penang Island from a low-altitude flying autopilot aircraft (CropCam) to generate land use/land cover (LULC) map of the test area. The CropCam was flown at an average altitude of 320 meters over the ground while capturing images which were taken during two flying missions for the duration of approximately 15 and 20 minutes respectively. The CropCam was equipped with a digital camera as a sensor to capture the GPS points based digital images according to the present time to ensure the mosaic of the digital images. Forty one images were used in providing a mosaic image of a bigger coverage of area (full panorama). Training samples were collected simultaneously when the CropCam captured the images by using hand held GPS. Supervised classification techniques, such as the maximum likelihood, minimum-to-distance, and parallelepiped were applied to the panoramic image to generate LULC map for the study area. It was found that the maximum likelihood classifier produce superior results and achieved a high degree of accuracy. The results indicated that the CropCam equipped with a high resolution digital camera can be useful and suitable tool for the tropical region, and this technique could reduce the cost and time of acquiring images for LULC mapping.
    Matched MeSH terms: Altitude
  5. Euthanasia in Malaysia: opinions and controversies
    Asma MA, Vaishnavi J, Chan L
    JUMMEC, 2002;7:92-99.
    Euthanasia is one of the most controversial topics of the 21st century after cloning and genetic engineering. Has this issue arisen now due to changes in attitude and perception on life of the modem society? This project was undertaken to study the opinions of 2 selected groups of people and secondly, to highlight the legal, ethical and religious controversies on euthanasia. Two groups comprising medical undergraduates and medical personnel were given a questionnaire pertaining 10 his/her opinion and altitude towards euthanasia. The second part of the project was conducted via interviews. The overall opinion from 399 respondents showed that 67.91% are against the practice of euthanasia. Religion is a powerful force against it as Malaysians in general are God-fearing people. There should be proper guidelines explaining how a doctor should respond to patients or family members of patients who request for euthanasia to be performed. It is not legal in Malaysia, but the court has the inherent power to permit it should a particular case have substantial reasoning and evidence. In conclusion, the level of awareness on euthanasia among medical staff and undergraduates is satisfactory. However, most of them do not approve euthanasia in Malaysia.
    Matched MeSH terms: Altitude
  6. Fulltext Global biogeographic patterns in bipolar moss species
    Biersma EM, Jackson JA, Hyvönen J, Koskinen S, Linse K, Griffiths H, et al.
    R Soc Open Sci, 2017 Jul;4(7):170147.
    PMID: 28791139 DOI: 10.1098/rsos.170147
    A bipolar disjunction is an extreme, yet common, biogeographic pattern in non-vascular plants, yet its underlying mechanisms (vicariance or long-distance dispersal), origin and timing remain poorly understood. Here, combining a large-scale population dataset and multiple dating analyses, we examine the biogeography of four bipolar Polytrichales mosses, common to the Holarctic (temperate and polar Northern Hemisphere regions) and the Antarctic region (Antarctic, sub-Antarctic, southern South America) and other Southern Hemisphere (SH) regions. Our data reveal contrasting patterns, for three species were of Holarctic origin, with subsequent dispersal to the SH, while one, currently a particularly common species in the Holarctic (Polytrichum juniperinum), diversified in the Antarctic region and from here colonized both the Holarctic and other SH regions. Our findings suggest long-distance dispersal as the driver of bipolar disjunctions. We find such inter-hemispheric dispersals are rare, occurring on multi-million-year timescales. High-altitude tropical populations did not act as trans-equatorial 'stepping-stones', but rather were derived from later dispersal events. All arrivals to the Antarctic region occurred well before the Last Glacial Maximum and previous glaciations, suggesting that, despite the harsh climate during these past glacial maxima, plants have had a much longer presence in this southern region than previously thought.
    Matched MeSH terms: Altitude
  7. Fulltext Fish biodiversity and assemblages along the altitudinal gradients of tropical mountainous forest streams
    Soo CL, Nyanti L, Idris NE, Ling TY, Sim SF, Grinang J, et al.
    Sci Rep, 2021 Aug 19;11(1):16922.
    PMID: 34413385 DOI: 10.1038/s41598-021-96253-3
    Knowledge of the fundamental aspects of ecology such as the patterns of fish species distribution and biodiversity in the forest streams is the first and basic step to develop effective conservation strategies. Yet, studies on altitudinal changes of fish composition and assemblages in Bornean forest streams are scarce despite being one of the hotspots of biodiversity conservation. Hence, surveys on freshwater fish composition along the altitudinal gradients of the Baleh River Basin in Sarawak, Borneo were conducted from April 2014 to August 2015. The Baleh River Basin was divided into seven altitudinal groups with a total of 72 stations. Group elevation ranged from 53 to 269 m above sea level. The fish samples and environmental parameters were taken concurrently during samplings. A total of 3565 specimens belonging to six orders, 14 families, and 76 species were found in the present study. The most dominant family in the Baleh River Basin was Cyprinidae (74.4%), followed by Gastromyzontidae (16.2%) while the most dominant species was Tor tambra (12.9%), followed by Lobocheilos ovalis (12.3%). Fish abundance significantly higher at high altitude sites than those at low altitude sites except for Mengiong River which has the lowest fish abundance despite with high elevation. Species richness was found significantly lower in midstream segment. Noticeable altitudinal gradient of fish assemblages was observed along the Baleh River except a discontinuity at the midstream segment which is attributable to the poorer quality inflow from the Mengiong River coupled with the meandering feature of the segment. Fish abundance was significantly and positively correlated with elevation, water pH and conductivity while negatively correlated with turbidity. Anthropogenic activities in the Baleh River Basin had altered the environmental variables thus disrupted the altitudinal gradient of fish assemblages. This phenomenon is apparent when the Canonical Correspondence Analysis (CCA) revealed that the first axis (CCA1) explained 42.5% of the variation and has positive loading on dissolved oxygen (DO) and negative loading on water conductivity; whereas CCA2 explained 37.5% of the variation and positively loaded on elevation, water pH, and DO. The results demonstrated that Gastromyzon fasciatus preferred more oxygenated water than Protomyzon sp., G. sp 1, and G. punctulatus although they are all from Gastromyzontidae family that inhabiting high altitude sites. Barbonymus schwanenfeldii was also found most abundant with elevated dissolved oxygen value. On the other hand, Rasbora volzii and R. hosii inhabiting lower altitude sites with less oxygenated and more acidic water.
    Matched MeSH terms: Altitude
  8. Phytosociology and ecological framework of forest tree species in the Toormang Valley, Dir Lower, Hindu Kush Range, Pakistan
    Hameed T, Ahmad I, Ullah S, Subramaniyan V, Ali I, Hussain H, et al.
    Braz J Biol, 2024;84:e282479.
    PMID: 39230079 DOI: 10.1590/1519-6984.282479
    The phytosociological survey was conducted during 2018-2020. The research area was classified into five ecological zones based on habitat, physiognomy and species composition. Pc-Ord software was used for cluster analysis and four vegetation communities were established. The Quercus baloot-Quercus incana community is situated in Sair at an altitude of 1196 (mean ± SE) m altitude with a 14.1 ± 0 slope angle and contains eleven tree species. The Pinus wallichiana- Ailanthus altissima community had a relatively small number of tree species reported in Shakawlie at 1556 (mean ± SE) with a 17.5 ± 0 slope angle. The Pinus wallichiana- Quercus incana community is distributed in Wali Kandao and Mangi Kandao at altitudes of 2030.5 (mean ± SE) m and the slope angle was 19.2 ± 1.4. This community possesses a total of twenty-one tree species and is highly diverse. Similarly, the Populus alba - Platanus orientalis group was present in Banr Pate, with an altitude of 1613 (mean ± SE) m and a 16.3 slope angle. The principal component analysis (PCA) and non-metric multidimensional scaling (NMS) ordination methods were applied to study the relationships between ecological and soil variables with trees species. The NMS ordination of axis 1 was significantly correlated with Sand% (p<0.2), Nitrogen% (p<0.1) and Pb (mg/kg) (r= 0.876751, p<0.05), while the ordination of axis 2 was significantly correlated with Silt% (p<0.2), Sand% (p<0.2), Organic matter% (p<0.2), K (mg/kg) (r=0.882433, p<0.02), Fe (mg/kg)(r=0.614833, p<0.2), Ca (mg/kg) (r=0.721712, p< 0.2) and Zn (mg/kg) (r=0.609545, p<0.2). Similarly, the PCA ordination of axis 1 revealed that it was significantly correlated with phosphorus, calcium and slope angle, while that of axis 2 was significantly correlated with altitude, zinc and manganese.
    Matched MeSH terms: Altitude
  9. Distribution of detritivores in tropical forest streams of peninsular Malaysia: role of temperature, canopy cover and altitude variability
    Che Salmah MR, Al-Shami SA, Abu Hassan A, Madrus MR, Nurul Huda A
    Int J Biometeorol, 2014 Jul;58(5):679-90.
    PMID: 23483291 DOI: 10.1007/s00484-013-0648-9
    The diversity and abundance of macroinvertebrate shredders were investigated in 52 forested streams (local scale) from nine catchments (regional scale) covering a large area of peninsular Malaysia. A total of 10,642 individuals of aquatic macroinvertebrates were collected, of which 18.22% were shredders. Biodiversity of shredders was described by alpha (αaverage), beta (β) and gamma diversity (γ) measures. We found high diversity and abundance of shredders in all catchments, represented by 1,939 individuals (range 6-115 and average per site of 37.29±3.48 SE) from 31 taxa with 2-13 taxa per site (αaverage=6.98±0.33 SE) and 10-15 taxa per catchment (γ=13.33±0.55 SE). At the local scale, water temperature, stream width, depth and altitude were correlated significantly with diversity (Adj-R2=0.205). Meanwhile, dissolved oxygen, stream velocity, water temperature, stream width and altitude were correlated to shredder abundance (Adj-R2=0.242). At regional scale, however, water temperature was correlated negatively with β and γ diversity (r2=0.161 and 0.237, respectively) as well as abundance of shredders (r2=0.235). Canopy cover was correlated positively with β diversity (r2=0.378) and abundance (r2=0.266), meanwhile altitude was correlated positively with β (quadratic: r2=0.175), γ diversity (quadratic: r2=0.848) as well as abundance (quadratic: r2=0.299). The present study is considered as the first report describing the biodiversity and abundance of shredders in forested headwater streams across a large spatial scale in peninsular Malaysia. We concluded that water temperature has a negative effect while altitude showed a positive relationship with diversity and abundance of shredders. However, it was difficult to detect an influence of canopy cover on shredder diversity.
    Matched MeSH terms: Altitude
  10. Habitat heterogeneity and niche structure of trees in two tropical rain forests
    Potts MD, Davies SJ, Bossert WH, Tan S, Nur Supardi MN
    Oecologia, 2004 May;139(3):446-53.
    PMID: 14997378
    Dispersal-assembly theories of species coexistence posit that environmental factors play no role in explaining community diversity and structure. Dispersal-assembly theories shed light on some aspects of community structure such as species-area and species-abundance relationships. However, species' environmental associations also affect these measures of community structure. Measurements of species' niche breadth and overlap address this influence. Using a new continuous measure of niche and a dispersal-assembly null model that maintains species' niche breadth and aggregation, we tested two hypotheses assessing the effects of habitat heterogeneity on the ability of dispersal-assembly theories to explain community niche structure. We found that in both homogenous and heterogeneous environments dispersal-assembly theories cannot fully explain observed niche structure. The performance of the dispersal-assembly null models was particularly poor in heterogeneous environments. These results indicate that non-dispersal based mechanisms are in part responsible for observed community structure and measures of community structure which include species' environmental associations should be used to test theories of species diversity.
    Matched MeSH terms: Altitude
  11. Fulltext Evidence for strong, widespread chlorine radical chemistry associated with pollution outflow from continental Asia
    Baker AK, Sauvage C, Thorenz UR, van Velthoven P, Oram DE, Zahn A, et al.
    Sci Rep, 2016 11 15;6:36821.
    PMID: 27845366 DOI: 10.1038/srep36821
    The chlorine radical is a potent atmospheric oxidant, capable of perturbing tropospheric oxidative cycles normally controlled by the hydroxyl radical. Significantly faster reaction rates allow chlorine radicals to expedite oxidation of hydrocarbons, including methane, and in polluted environments, to enhance ozone production. Here we present evidence, from the CARIBIC airborne dataset, for extensive chlorine radical chemistry associated with Asian pollution outflow, from airborne observations made over the Malaysian Peninsula in winter. This region is known for persistent convection that regularly delivers surface air to higher altitudes and serves as a major transport pathway into the stratosphere. Oxidant ratios inferred from hydrocarbon relationships show that chlorine radicals were regionally more important than hydroxyl radicals for alkane oxidation and were also important for methane and alkene oxidation (>10%). Our observations reveal pollution-related chlorine chemistry that is both widespread and recurrent, and has implications for tropospheric oxidizing capacity, stratospheric composition and ozone chemistry.
    Matched MeSH terms: Altitude
  12. Fulltext Influence of Exposure at Different Altitudes on the Executive Function of Plateau Soldiers-Evidence From ERPs and Neural Oscillations
    Wei X, Ni X, Zhao S, Chi A
    Front Physiol, 2021;12:632058.
    PMID: 33935798 DOI: 10.3389/fphys.2021.632058
    This study investigates the changes in soldiers' brain executive function at different altitude environments and their relationship with blood oxygen saturation. Stratified sampling was conducted in different altitude 133 active-duty soldiers who were stationed in Weinan (347 m, n = 34), Nyingchi (2,950 m, n = 32), Lhasa (3,860 m, n = 33), and Nagqu (4,890 m, n = 34) for 2 years. The Go/NoGo paradigm with event-related potentials (ERPs) and event-related oscillations (EROs) was used to explore the time and neural oscillation courses of response inhibition. Behavioral results revealed that at the 4,890-m altitude area, the soldiers had the highest false alarm rate, the longest reaction time, and the slowest information transmission rate. The electrophysiological results revealed that NoGo-N2 and N2d decreased with increasing altitude, with significant changes at 3,860 m; the amplitudes of NoGo-P3 and P3d in plateau groups were significantly more negative than the plain and changed significantly at 2,950 m. The results of correlation analysis showed that NoGo-P3 was negatively correlated with altitude (r = -0.358, p = 0.000), positively correlated with SpO2 (r = 0.197, p = 0.041) and information translation rate (ITR) (r = 0.202, p = 0.036). P3d was negatively correlated with altitude (r = -0.276, p = 0.004) and positively correlated with ITR (r = 0.228, p = 0.018). N2d was negatively correlated with ITR (r = 0.204, p = 0.034). The power spectrum analysis of NoGo-N2 and NoGo-P3 showed that the power of δ and θ bands at the plateau area was significantly lower than the plain area and showed a significant step-by-step decrease; the α-band power increases significantly only in the area of 4,890 m. The effect of chronic hypoxia exposure at different altitudes of the plateau on the response inhibition of soldiers was manifested: 3,860 m was the altitude at which the brain response inhibition function decreased during the conflict monitoring stage, and 2,950 m was the altitude at which it dropped during the response inhibition stage. In addition, the soldier's brain's executive function was closely related to SpO2, and a reduction in SpO2 may lead to a decline in response inhibition.
    Matched MeSH terms: Altitude
  13. Quantitative comparisons of lung structure of adult domestic fowl and red jungle fowl, with reference to broiler ascites
    Vidyadaran MK, King AS, Kassim H
    Avian Pathol, 1990 Jan;19(1):51-8.
    PMID: 18679913
    A stereological comparison has been made of the structure of the lungs of the adult female domestic fowl and its wild progenitor the Red Jungle Fowl. The volume of the lung per unit body weight of the domestic bird is between 20 and 33% smaller than that of the wild bird. The domestic fowl has partly compensated for this by increasing the surface area for gas exchange per unit volume of exchange tissue. However, the blood-gas tissue barrier is about 28% thicker in the domestic fowl than in the Red Jungle Fowl, and this has led to a 25% lower anatomical diffusing capacity for oxygen of the blood-gas tissue barrier per unit body weight in the domestic fowl. These structural characteristics may make the modern domestic fowl vulnerable to stress factors such as altitude, cold, heat or air pollution by predisposing to hypoxaemia and perhaps thence to ascites.
    Matched MeSH terms: Altitude
  14. Fulltext Spatiotemporal patterns of anuran functional diversity in temperate montane forests
    Sun ZJ, Zhu W, Zhu WB, Zhao CL, Liao CL, Zou B, et al.
    Zool Res, 2021 Jul 18;42(4):412-416.
    PMID: 34075734 DOI: 10.24272/j.issn.2095-8137.2020.341
    Functional diversity is an integrative approach to better understand biodiversity across space and time. In the present study, we investigated the spatiotemporal patterns (i.e., elevation and season) and environmental determinants of anuran functional diversity on Tianping Mountain, northwest Hunan, China. Specifically, 10 transects were established from low (300 m a.s.l.) to high (1 492 m a.s.l.) elevations, and anuran communities were sampled in spring, early summer, midsummer, and autumn in 2017. Four functional diversity indices were computed for each transect in each season using ecomorphological functional traits. Our results demonstrated that these indices had contrasting responses to increasing elevations. However, they did not differ significantly among seasons in terms of temporal patterns. Interestingly, the unique spatiotemporal functional diversity patterns were impacted by distinct environmental variables, such as leaf litter cover, water temperature, number of trees, and water conductivity.
    Matched MeSH terms: Altitude
  15. Fulltext Three new species of Grouvellinus Champion, 1923 from Maliau Basin, Sabah, Borneo, discovered by citizen scientists during the first Taxon Expedition (Insecta, Coleoptera, Elmidae)
    Freitag H, Pangantihon CV, Njunjić I
    Zookeys, 2018.
    PMID: 29740222 DOI: 10.3897/zookeys.754.24276
    Further results are presented of the first field course at Maliau Basin, Malaysian Borneo organized by Taxon Expeditions, an organization which enables citizen scientists to be directly involved in taxonomic discoveries. Three new species of the aquatic beetle genus Grouvellinus Champion, 1923, namely G. leonardodicaprioisp. n., G. andrekuipersisp. n., and G. questsp. n. were collected jointly by the citizen scientists and taxonomists during the fieldwork in Maliau Basin. Material was mainly sampled from sandstone bottom rocks of blackwater streams at altitudes between 900 m and 1,000 m using fine-meshed hand-nets. The genus is widely distributed in the Oriental and Palearctic regions, but these are the first records from the island of Borneo.
    Matched MeSH terms: Altitude
  16. Distribution of Lichen Flora at Different Altitudes of Gunung Machincang, Langkawi Islands, Malaysia
    Shahrizim Zulkifly, Young SK, Mohamed Abudl Majid, Amir Feisal Merican
    Sains Malaysiana, 2011;40:1201-1208.
    Lichen samples were collected from Gunung Machincang, Langkawi Islands based on an alternation of altitudes, which are 0, 300 and above 600 m. Morphological identification resulted in 15 genera of microlichens (crustose) and five genera of macrolichens (foliose) and they fall under 14 families. As the altitude increases, the number of foliose type of lichen also increased. The common microlichens obtained were from the Family of Graphidaceae and can be found from the sea level right up to the peak of Gunung Machincang. The most common crustose lichens found were Heterodermia sp., while Eugenia sp. is the most common tree habitat for lichens in Gunung Machincang, Langkawi Islands. This study represents the first record of lichens in Gunung Machincang, Langkawi Islands, Malaysia.
    Matched MeSH terms: Altitude
  17. Aquatic insect functional feeding groups in a mountain stream with a series of check dams in northern Thailand
    Phuchiwan Suriyawong, Elizabeth A. Bergey
    Sains Malaysiana, 2018;47:1379-1386.
    A series of check dams (or small dams in shallow streams) have been placed on many streams throughout Thailand and
    the number of them continue to increase. Check dam construction activities have been emphasized by the government
    and private sector entities over the last decade to prevent severe flood or drought due to changes in rainfall patterns. This
    study evaluated distribution of functional feeding groups (FFG) in a stream with a high density of check dams. Twelve
    sampling sites at three altitudes (500, 900 and 1500 m asl) included undammed and nearby dammed sections (above
    and below check dams) were used. Aquatic insects were collected monthly at each site for a year and categorized into
    FFG. Aquatic insect composition of undammed and above dam sites was different. Abundance within each FFG at above
    dam sites significantly differed from undammed sites. Taxonomic richness at 1500 and 900 m altitudes was decreased
    at above dam sites compared with the corresponding undammed sites, whereas above dam sites of 500 m altitude had
    higher richness than undammed site. High abundance of predators and collector-gatherers associated with reservoirs
    and fine sediment accumulation above dams, where filter-feeders were scarce. Shredder abundance varied among sites
    and was highest where leaf packs were most abundant. Scrapers were least abundant group and inconsistent with the
    dams. Distribution of FFG was similar to changes in other regulated streams. The composition of FFG reflected the
    stream ecosystem conditions through adaptation of communities to stream habitat and food resources, including those
    associated with check dam construction.
    Matched MeSH terms: Altitude
  18. Evolution of endemism on a young tropical mountain
    Merckx VS, Hendriks KP, Beentjes KK, Mennes CB, Becking LE, Peijnenburg KT, et al.
    Nature, 2015 Aug 20;524(7565):347-50.
    PMID: 26266979 DOI: 10.1038/nature14949
    Tropical mountains are hot spots of biodiversity and endemism, but the evolutionary origins of their unique biotas are poorly understood. In varying degrees, local and regional extinction, long-distance colonization, and local recruitment may all contribute to the exceptional character of these communities. Also, it is debated whether mountain endemics mostly originate from local lowland taxa, or from lineages that reach the mountain by long-range dispersal from cool localities elsewhere. Here we investigate the evolutionary routes to endemism by sampling an entire tropical mountain biota on the 4,095-metre-high Mount Kinabalu in Sabah, East Malaysia. We discover that most of its unique biodiversity is younger than the mountain itself (6 million years), and comprises a mix of immigrant pre-adapted lineages and descendants from local lowland ancestors, although substantial shifts from lower to higher vegetation zones in this latter group were rare. These insights could improve forecasts of the likelihood of extinction and 'evolutionary rescue' in montane biodiversity hot spots under climate change scenarios.
    Matched MeSH terms: Altitude*
  19. Fulltext Central scotoma at near top of Mount Everest – a case report of bilateral high altitude retinopathy
    Nazrina Hassan, Yong Meng Hsien, Wan Haslina Wan Abdul Halim, Norshamsiah Md Din
    Malaysian Journal of Medicine and Health Sciences, 2019;15(106):94-94.
    MyJurnal
    Introduction: High altitude retinopathy (HAR) is part of high altitude illness (HAI) which includes acute mountain sickness, high altitude cerebral oedema and pulmonary oedema. We present a case of bilateral HAR with right eye central scotoma during Mount Everest expedition. Case description: A 37-year-old lady presented with decreased right eye (OD) vision and central scotoma during ascending to the top of Mount Everest at 5100m. She developed respiratory symptoms with shortness of breath at the same time and warranted her a rapid descend on day eight of her excursion. Ocular examination revealed visual acuity of 6/36 OD and 6/6 left eye (OS). Both pupils were normal without relative afferent pupillary defect. Anterior segment and intraocular pressure were unremarkable. Fundus examination revealed bilateral multiple retinal haemorrhages along vascular arcades, with macula involvement in the right eye only. Otherwise there was no sign of optic disc swelling, vascular sheathing or choroidal involvement. Optical coherence tomography (OCT) of the macula showed hyperreflectivity changes on the right fovea at the level of superficial nerve fiber layer. Diagnosis of bilateral HAR was made and treated conservatively. She was also diag-nosed with HAI with acute pulmonary oedema and pneumonia by the treating physician. The retinal haemorrhages started to resolve after two weeks with full recovery of vision in ten weeks. Conclusion: With increasing popularity of mountaineering, ophthalmologists should be prepared to recognise HAR as part of HAI. Visual impairment depends on the location and extent of the lesions. HAR is self-limiting with good prognosis but can be associated with poten-tially fatal conditions of HAI e.g. pulmonary oedema in our case.
    Matched MeSH terms: Altitude; Altitude Sickness
  20. Fulltext The effect of acute pomegranate extract supplementation on oxygen uptake in highly-trained cyclists during high-intensity exercise in a high altitude environment
    Crum EM, Che Muhamed AM, Barnes M, Stannard SR
    J Int Soc Sports Nutr, 2017;14:14.
    PMID: 28572749 DOI: 10.1186/s12970-017-0172-0
    BACKGROUND: Recent research has indicated that pomegranate extract (POMx) may improve performance during aerobic exercise by enhancing the matching of vascular oxygen (O2) provision to muscular requirements. POMx is rich in ellagitannin polyphenols and nitrates (NO3-), which are both associated with improvements in blood flow and O2 delivery. Primarily, this study aimed to determine whether POMx improves performance in a cycling time trial to exhaustion at 100%VO2max (TTE100%) in highly-trained cyclists. In addition, we investigated if the O2 cost (VO2) of submaximal exercise was lower with POMx, and whether any changes were greater at high altitude where O2 delivery is impaired.

    METHODS: Eight cyclists exercised at three submaximal intensities before completing a TTE100% at sea-level (SEA) and at 1657 m of altitude (ALT), with pre-exercise consumption of 1000 mg of POMx or a placebo (PLAC) in a randomized, double-blind, crossover design. Data were analysed using a three way (treatment x altitude x intensity) or two-way (treatment x altitude) repeated measures ANOVA with a Fisher's LSD post-hoc analysis. Significance was set at p ≤ 0.05. The effect size of significant interactions was calculated using Cohen's d.

    RESULTS: TTE100% performance was reduced in ALT but was not influenced by POMx (p > 0.05). Plasma NO3- were 10.3 μmol greater with POMx vs. PLAC (95% CI, 0.8, 19.7,F1,7 = 7.83, p  0.05). Submaximal VO2 values were not affected by POMx (p ≥ 0.05).

    CONCLUSIONS: The restoration of SEA VO2 values at ALT is likely driven by the high polyphenol content of POMx, which is proposed to improve nitric oxide bioavailability. Despite an increase in VO2, no change in exercise performance occurred and therefore this study does not support the use of POMx as an ergogenic supplement.

    Matched MeSH terms: Altitude*
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