Unmodified Area Research Articles

Modulation of GaAs nanowire growth by pre-treatment of Si substrate using a Ga focused ion beam

We reveal a novel phenomenon observed after self-catalytic growth of GaAs nanowires (NWs) on Si(111) substrates treated with a Ga focused ion beam (FIB). Depending on the ion dose, NW arrays with various geometrical parameters can be obtained. A minor treatment of the substrate enables a slight increase in the surface density of NWs relative to an unmodified substrate area. As the ion dose is increased up to ∼0.1 pC μm−2, the growth of GaAs NWs and nanocrystals is suppressed. However, a further increase in the ion dose stimulates the crystal growth leading to the formation of extremely thin NWs (39 ± 5 nm) with a remarkably high surface density of up to 15 μm−2. Resting upon an analysis of the surface structure before and after stages of ion-beam treatment, ultra-high vacuum annealing and NW growth, we propose a mechanism underlying the phenomenon observed. We assume that the chemical interaction between embedded Ga ions and a native Si oxide layer leads either to the enhancement of the passivation properties of the oxide layer within FIB-modified areas (at low and middle ion doses), or to the etching of the passivating oxide layer by excess Ga atoms, resulting in the formation of pores (at high ion doses). Due to this behavior, local fabrication of GaAs NW arrays with a diverse range of characteristics can be implemented on the same substrate. This approach opens a new way for self-catalytic growth of GaAs NWs.

A multi-scale coupled productivity prediction model for conflagration compression fracturing of shale

A multi-fracture pressure flow regime coupled productivity prediction model considering shale gas adsorption and desorption, mass transfer and diffusion and cross-scale zoning was established based on cross-scale seepage characterization in unmodified area, interstitial matrix area, main fracture area, branched micro-fracture area and broken damage area formed from by conflagration compression fracturing. Then, geometric similarity, hydropower similarity and coupled iteration were used to build the model and complete the calculation. Finally, the effects of regional cross-scale seepage, number of fractures, production pressure difference, and fracture zone scale on gas well productivity were analyzed. The following results were obtained. First, the seepage flow of shale gas in different fractured areas is a continuous changing process. Among them, the unaffected area is dominated by transition flow and slip flow while continuous flow exists in the microfracture area-wellbore broken area and artificial fracture area. Second, the productivity of gas wells increases with the increase of fracture length and number, but the productivity increase tends to be stable after the fracture length exceeds 2 m. It is worth to mention that the increase of the number of fractures is more conducive to improving the productivity of shale gas under this condition. Third, when the number of high energy gas fractures is 6, its mining capacity is equivalent to that of hydraulic fracturing fractures with a half-fracture length of about 100 m. Fourth, when the production pressure difference exceeds 22 MPa, the free gas production capacity shows a decreasing trend. Therefore, the preferred production pressure difference is about 22 MPa. Fifth, the greater the number of artificial fractures, the greater the contribution of the increase in the diffusion coefficient to productivity, and the existence of wellbore fracture zone is also conducive to the stimulation of gas wells.

Deepfake noise investigation and detection

The fast development of Deepfake has brought huge current and potential future negative impacts to our daily lives. As the circulating popular Deepfake videos have become difficult to be distinguished by human eyes, various Deepfake detection approaches have been attempted using deep learning models. However, even though some existing detection methods have achieved reasonable detection performance with respect to the statistical evaluation metrics, the actual underlying Deepfake forensic traces have been barely discussed. In this study, we investigate the special forensic noise traces within Deepfake image frames and propose a noise-based Deepfake detection model approach using a deep neural network. We train a Siamese noise extractor using a novel face-background strategy to investigate different forensic noise traces of a synthesized face area and an unmodified background area. A similarity matrix module is proposed to analyze the forensic noise trace difference between a cropped face square and a cropped background square from a candidate image frame for the Deepfake detection task. As a result, our proposed model trained on the high-quality Celeb-DF dataset has achieved state-of-the-art performance with 99.15% accuracy and 99.92% AUC score on the in-dataset testing set and 88.95% AUC score on the highly difficult unknown-attack Deepfake video dataset. Furthermore, the visualization of the Deepfake forensic noise traces has shown the explicit distinction between synthesized faces and any unmodified area. We believe that the visualized evidence could provide better proof of Deepfake detection results rather than simply the statistical evaluation numbers.

Increases in subsistence farming due to land reform have negligible impact on bird communities in Zimbabwe.

Habitat alterations resulting from land‐use change are major drivers of global biodiversity losses. In Africa, these threats are especially severe. For instance, demand to convert land into agricultural uses is leading to increasing areas of drylands in southern and central Africa being transformed for agriculture. In Zimbabwe, a land reform programme provided an opportunity to study the biodiversity response to abrupt habitat modification in part of a 91,000 ha dryland area of semi‐natural savannah used since 1930 for low‐level cattle ranching. Small‐scale subsistence farms were created during 2001–2002 in 65,000 ha of this area, with ranching continuing in the remaining unchanged area. We measured the compositions of bird communities in farmed and ranched land over 8 years, commencing one decade after subsistence farms were established. Over the study period, repeated counts were made along the same 45 transects to assess species' population changes that may have resulted from trait‐filtering responses to habitat disturbance. In 2012, avian species' richness was substantially higher (+8.8%) in the farmland bird community than in the unmodified ranched area. Temporal trends over the study period showed increased species' richness in the ranched area (+12.3%) and farmland (+6.8%). There were increased abundances in birds of most sizes, and in all feeding guilds. New species did not add new functional traits, and no species with distinctive traits were lost in either area. As a result, species' diversity reduced, and functional redundancy increased by 6.8% in ranched land. By 2020, two decades after part of the ranched savannah was converted into farmland, the compositions of the two bird communities had both changed and became more similar. The broadly benign impact on birds of land conversion into subsistence farms is attributed to the relatively low level of agricultural activity in the farmland and the large regional pool of nonspecialist bird species.

Habitat preference of the Indian Pangolin Manis crassicaudata inhabiting Margalla Hills National Park, Islamabad, Pakistan

The Indian Pangolin Manis crassicaudata, is an ‘Endangered’ mammal species native to Pakistan but facing a risk of extinction due to hunting pressure for its scales used in trade. The current study investigated habitat preference of this unique species in the Margalla Hills National Park, Islamabad, from September 2011 to August 2012. Three habitat types, viz, human vicinity area, agricultural land, and wild/natural area, were searched for recording signs of Indian Pangolin. Data on habitat preference was collected from direct and indirect signs of the species by monitoring 85 line transects, each measuring 500m in length and 50m in width, in 17 different sampling sites. A total of 323 signs of Indian Pangolin were recorded including 299 burrows, 10 live sightings, and 14 scats of the species. The maximum number of signs were recorded in wild or unmodified natural area (55.1%), followed by those in vicinity to human use area (20.12%), while the least (24.76%) were found in agricultural area. Statistical comparison using one-way analysis of variance of pangolin field signs, among three different types of habitats studied, differed significantly (df= 48, F= 13.723, p <0.001). Similarly, LSD analysis further revealed that field signs of Indian pangolin recorded on natural or wild habitat significantly differed from those which were on agricultural land and human vicinity area (p <0.001). The study concludes that the Indian Pangolin prefers habitats in the wild or natural area over those close to human vicinity and agricultural lands.

Kraft Lignin as Electrode Material for Sustainable Electrochemical Energy Storage

AbstractElectrochemical energy storage using lignin as a renewable electrode material is a cheap and sustainable approach for future organic batteries. Previous reports mainly focus on lignosulfonates (LS) or composites with conductive polymer additives with inherent problems, such as still expensive monomers. Here, composite electrodes are used from more available Kraft lignin and sustainable conductive carbon. Charge storage is evaluated in terms of electrical double layer storage and redox reactions, aiming at a better understanding of desired lignin properties for electrochemical energy storage. Using unmodified, commercial lignin and high surface area conductive carbon, reasonable capacity of ≈80 mAh g−1 is achieved in samples in which a thin layer of lignin covers the interface of high surface area carbon. Non‐faradaic contribution to charge storage is as large as in comparable pure carbon electrodes, and redox reactions in lignin contribute to additional, faradaic charge storage, significantly enhancing capacity in these systems. Resulting electrodes are cheap, reliable, and stable.

Waveguides and proportional beam splitters in bulk poly(methyl methacrylate) produced by direct femtosecond-laser inscription

Waveguides fabricated by direct femtosecond-laser inscription were reported in bulk poly(methyl methacrylate) (PMMA). Optimization of waveguide structures was conducted and 1×2 beam splitters with equal and proportional splitting ratio were fabricated. Three-dimensional structures of 1×4 beam splitters were also achieved based on 1×2 beam splitters. The largest change of the refractive index between femtosecond laser modified area and unmodified area was estimated to be 1.1×10−3. The minimum insertion loss of the single-mode waveguide measured with the He–Ne laser at the wavelength of 632.8nm was 4.32dB and propagation loss was calculated to be as low as 3.57dB/cm.

Optimization of waveguide structures for beam splitters fabricated in fused silica by direct femtosecond-laser inscription

Abstract The Type-I waveguides fabricated by femtosecond laser inscription were reported in fused silica. Optimization of waveguide structures was conducted for fabricating 1×2 and 1×4 beam splitters. The change of the refractive index between femtosecond laser modified area and unmodified area was estimated to be 9×10 −4 . The minimum loss of the waveguides measured with the He–Ne laser at the wavelength of 632.8 nm was determined to be as low as 1.34 dB.

A Broad Transition from Cloud Forest to Páramo Characterizes an Undisturbed Treeline in Parque Nacional Llanganates, Ecuador

This study aimed at investigating the vegetation pattern associated with the transition from upper northern Andean cloud forest to páramo grassland in a relatively unmodified area in Ecuador’s Eastern Cordillera. Single 20 × 10 m plots were randomly placed in representative sites along an altitudinal gradient from continuously wet Andean montane cloud forest at 3400–3700 m to páramo grassland at 3900–4000 m. Also sampled was a disjunct stand of the stem-rosette Espeletia pycnophylla var. llanganatensis, some 200 km south of the limit of the otherwise continuous distribution of this genus. Several physical and chemical soil factors, including temperature at -30 cm, were determined. Visual estimates of cover in four life-form classes (trees, shrubs, herbs, ground cover) at each site revealed similarities related to their relative proximity along an elevation gradient. Stands with a tree cover were more species-rich than those without, due largely to the differential distribution of the woody flora. No abrupt discontinuity occurred in the mix of species along this gradient. Soil temperature and altitude were the most important factors of those measured to explain the variability in plant community structure and composition. There was no clear zonation evident along the altitudinal gradient, with vegetation structure and floristics displaying continuous variation. No clear upper forest limit was differentiated. The isolated presence of Espeletia in the area is discussed, but the theory about its origin remains speculative.

QT Interval Heterogeneities Induced Through Local Epicardial Warming/Cooling. An Experimental Study

Introduction and objectivesAbnormal QT interval durations and dispersions have been associated with increased risk of ventricular arrhythmias. The present study examines the possible arrhythmogenic effect of inducing QT interval variations through local epicardial cooling and warming. MethodsIn 10 isolated rabbit hearts, the temperatures of epicardial regions of the left ventricle were modified in a stepwise manner (from 22°C to 42°C) with simultaneous electrogram recording in these regions and in others of the same ventricle. QT and activation-recovery intervals were determined during sinus rhythm, whereas conduction velocity and ventricular arrhythmia induction were determined during programmed stimulation. ResultsIn the area modified from baseline temperature (37°C), the QT (standard deviation) was prolonged with maximum hypothermia (195 [47] vs 149 [12] ms; P<.05) and shortened with hyperthermia (143 [18] vs 152 [27] ms; P<.05). The same behavior was displayed for the activation-recovery interval. The conduction velocity decreased with hypothermia and increased with hyperthermia. No changes were seen in the other unmodified area. Repetitive responses were seen in 5 experiments, but no relationship was found between their occurrence and hypothermia or hyperthermia (P>.34). ConclusionsIn the experimental model employed, local variations in the epicardial temperature modulate the QT interval, activation-recovery interval, and conduction velocity. Induction of heterogeneities did not promote ventricular arrhythmia occurrence.

Heterogeneidades inducidas en el intervalo QT mediante enfriamiento/calentamiento epicárdico local. Estudio experimental

Introduction and objectivesAbnormal QT interval durations and dispersions have been associated with increased risk of ventricular arrhythmias. The present study examines the possible arrhythmogenic effect of inducing QT interval variations through local epicardial cooling and warming. MethodsIn 10 isolated rabbit hearts, the temperatures of epicardial regions of the left ventricle were modified in a stepwise manner (from 22°C to 42°C) with simultaneous electrogram recording in these regions and in others of the same ventricle. QT and activation-recovery intervals were determined during sinus rhythm, whereas conduction velocity and ventricular arrhythmia induction were determined during programmed stimulation. ResultsIn the area modified from baseline temperature (37°C), the QT (standard deviation) was prolonged with maximum hypothermia (195 [47] vs 149 [12] ms; P<.05) and shortened with hyperthermia (143 [18] vs 152 [27] ms; P<.05). The same behavior was displayed for the activation-recovery interval. The conduction velocity decreased with hypothermia and increased with hyperthermia. No changes were seen in the other unmodified area. Repetitive responses were seen in 5 experiments, but no relationship was found between their occurrence and hypothermia or hyperthermia (P>.34). ConclusionsIn the experimental model employed, local variations in the epicardial temperature modulate the QT interval, activation-recovery interval, and conduction velocity. Induction of heterogeneities did not promote ventricular arrhythmia occurrence.Full English text available from: www.revespcardiol.org/en

Predicting the impacts of edge effects in fragmented habitats: Laurance and Yensen’s core area model revisited

An accurate estimate of the impact of edge effects is essential for the conservation management of threatened species in isolated habitat fragments. In a seminal paper, Laurance and Yensen (1991) developed the first generalized predictive model estimating the amount of edge-affected area and remaining unmodified core area in isolated fragments. Despite their conclusion that the core-area model should be applicable to all fragments, regardless of size or shape, the model has never been validated beyond the limited range of parameters under which the model was constructed. Here, we conduct a sensitivity test of the core-area model accounting for ecologically-realistic variation in fragment Shape Index (SI), and collinearity among shape, area and depth of edge influence (DEI). Using well-resolved GIS data for the South Island of New Zealand, we find substantial core-area model underestimates for large fragments (>10,000ha) with high SI values (>10.0), particularly at high DEI (>100m). To overcome this we reformulate the core-area model with a more accurate shape-specific exponent function, and test our new model against Laurance and Yensen’s core-area model and a null geometric model using an independently-derived GIS dataset for the North Island, New Zealand. Our new model provides a significantly better fit to the data. We conclude that past predictive applications of the core-area model have underestimated true core area, and we recommend our simple re-formulated model for estimating the degree of population and community responses to habitat fragmentation under ecologically-realistic scenarios of high patch shape complexity and large spatial extent of edge influence.

Deposition of conductivity-switching polyimide film by molecular layer deposition and electrical modification using scanning probe microscope

This Letter reports on the deposition of a conductivity-switching polyimide film as a recording medium formed by molecular layer deposition (MLD). It also reports on the electrical modification on it using a scanning probe microscope (SPM). The polyimide film is uniformly deposited on an Au surface by MLD. As the result of the electrical modification, highly conductive dots pattern with a narrow pitch of approximately 50 nm is successfully defined by applying pulsed voltages. The current ratio of the electrical modified area to unmodified area reached 300 at least.

Relation Between Friction and Plastic Deformation Examined by Using Periodic Asperity Arrays Fabricated on an AFM Multipurpose Cantilever

The relation between friction force and plastic deformation was determined by using FIB (focused ion beam)-processed multipurpose cantilevers for an AFM (atomic force microscope). First, a multipurpose cantilever consisting of a sliding block, parallel leaf spring, and hinge was made by using an FIB. Then, copper pyramids were rubbed against an unmodified area or periodic asperity arrays fabricated on the cantilever under loads of 23 to 960 nN. Under higher loads (∼900 nN), the friction coefficient measured for an asperity array was lower than that for an unmodified area and decreased with decreasing curvature radius of the asperity peak, and the specific volume change rate increased with decreasing curvature radius of the asperity peak.

Scanning tunneling microscope tip-induced anodization of titanium: Characterization of the modified surface and application to the metal resist process for nanolithography

Nanometer scale oxide patterns were fabricated on titanium (Ti) surfaces on the basis of scanning tunneling microscope (STM) tip-induced anodization. The spatial resolution of the method was limited to approximately 20 nm, owing to the surface roughness of the Ti film used. Chemical analyses of fabricated patterns by Auger electron spectroscopy proved that the surface chemical composition of the pattern was titanium dioxide (TiO2), and the oxide thickness on the pattern was certainly thicker than that of the native oxide on the unmodified area. A novel Ti-metal resist process for nanolithography based on STM tip-induced anodization was proposed. The Ti film on which anodized patterns were formed could be etched by hydrofluoric acid using the anodic oxide patterns as an etching mask. Ti lines of ∼60 nm in width were successfully fabricated by the present method.

Large-Scale Irrigation and Arbovirus Epidemiology, Kano Plain, Kenya1: I. Description of the area and preliminary studies on the mosquitoes2

During May and June 1969, the distribution and abundance of adult and larval mosquito populations were studied on an irrigation scheme designed for rice production in Nyanza Province, Kenya and compared with an unmodified ecosystem 12 km to the southwest. Twelve species, 4 anopheline and 8 culicine, were recorded as adults. Biting studies using human bait showed that activity was almost exclusively at night. Although the numbers taken in night catches at the 2 sites (23,641 and 22,966 respectively) were very similar, the species composition was different. In the village adjacent to the ricefields Anopheles gambiae Giles made up 65% of the catch, Mansonia uniformis Theo., 28% and Culex pipiens fatigans Weid., 5%, while in a village in the unmodified area, M. uniformis constituted 86% of the catch, A. gambiae less than 1% and only 3 C. p. fatigans were taken. Larvae of A. gambiae were most abundant in nursery padi while among older, denser plants C. antennatus Beck was the dominant species. In ecologically similar microhabitats in the unmodified area, A. gambiae was the dominant species although 4 times less abundant than in young padi; adult and larval abundance are related. Due to the cropping regime, 2 population peaks a year are to be expected. Elsewhere in East Africa arboviruses have been isolated from 4 of the species recorded here. Birds were abundant in the rice, particularly heron, stork and ibis, and 2 species, the Cattle Egret ( Bubulcus ibis ) and Sacred Ibis ( Threskiornis aethiopicus ), play a role in the maintenance Sindbis and West Nile viruses elsewhere in southern Africa. Rodents, particularly Arvicanthis niloticus and Mastomys natalensis , were found and could play a role in the epidemiology of arboviruses, rickettsial infections, plague and leptospirosis. Other diseases which may become associated with the irrigation scheme are considered.

Ricefield development and arbovirus epidemiology, Kano Plain, Kenya

During May and June 1969, adult and larval mosquito populations were compared in an unmodified area and in a newly irrigated area in Nyanza Province, Kenya. The numbers taken on human bait in 14 night catches in the two localities were 22,966 and 23,641 respectively. In a village in the unmodified area, Mansonia uniformis constituted 86% of the catch while in a village adjacent to the new ricefields Anopheles gambiae made up 65% of the catch and Culex fatigans 5%. Larvae of A. gambiae were most abundant in nursery rice while among older, denser plants C. antennatus was the dominant species. In ecologically similar microhabitats in the unmodified area, A. gambiae was the dominant species although 4 times less abundant than in young rice. Birds were abundant in the rice, particularly heron, stork and ibis. Rodents, particularly Arvicanthus niloticus and Mastomys natalensis were common. Viruses were isolated from M. uniformis, M. africana and A. gambiae and antibodies to o'nyong-nyong, chikungunya and Nyando viruses found in sera from school children.