Spatial distribution of degradation and deforestation of palm swamp peatlands and associated carbon emissions in the Peruvian Amazon.

The vast peat deposits in the Peruvian Amazon are crucial to the global climate. Palm swamp, the most extensive regional peatland ecosystem faces different threats, including deforestation and degradation due to felling of the dominant palm Mauritia flexuosa for fruit harvesting. While these activities convert this natural C sink into a source, the distribution of degradation and deforestation in this ecosystem and related C emissions remain unstudied. We used remote sensing data from Landsat, ALOS-PALSAR, and NASA's GEDI spaceborne LiDAR-derived products to map palm swamp degradation and deforestation within a 28 Mha area of the lowland Peruvian Amazon in 1990-2007 and 2007-2018. We combined this information with a regional peat map, C stock density data and peat emission factors to determine (1) peatland C stocks of peat-forming ecosystems (palm swamp, herbaceous swamp, pole forest), and (2) areas of palm swamp peatland degradation and deforestation and associated C emissions. In the 6.9 ± 0.1 Mha of predicted peat-forming ecosystems within the larger 28 Mha study area, 73% overlaid peat (5.1 ± 0.9 Mha) and stored 3.88 ± 0.12 Pg C. Degradation and deforestation in palm swamp peatlands totaled 535,423 ± 8,419 ha over 1990-2018, with a pronounced dominance for degradation (85%). The degradation rate increased 15% from 15,400 ha y-1 (1990-2007) to 17,650 ha y-1 (2007-2018) and the deforestation rate more than doubled from 1,900 ha y-1 to 4,200 ha y-1. Over 1990-2018, emissions from degradation amounted to 26.3 ± 3.5 Tg C and emissions from deforestation were 12.9 ± 0.5 Tg C. The 2007-2018 emission rate from both biomass and peat loss of 1.9 Tg C yr-1 is four times the average biomass loss rate due to gross deforestation in 2010-2019 reported for the hydromorphic Peruvian Amazon. The magnitude of emissions calls for the country to account for deforestation and degradation of peatlands in national reporting.

Predicting the results of chemical vapor deposition growth of suspended carbon nanotubes.

The successful growth of suspended carbon nanotubes is normally based on purely empirical results. Here we demonstrate the ability to predict the successful suspension of nanotubes across a range of trench widths by combining experimental growth data with a theoretical description of nanotube mechanics at the growth temperature. We show that rare thermal oscillations much larger than the rms amplitude combined with the large nanotube-substrate adhesion energy together are responsible for unsuccessful nanotube suspensions. We derive an upper limit on the number of deleterious nanotube-substrate interactions that can be tolerated before successful growth becomes impossible, and we are able to accurately explain literature reports of suspended nanotube growth. The methodology developed here should enable improved growth yields of suspended nanotubes, and it provides a framework in which to analyze the role of nanotube-substrate interactions during nanotube growth by chemical vapor deposition.

Discrimination between Bacillus species by impedance analysis of individual dielectrophoretically positioned spores.

We combine the use of dielectrophoretic positioning with electrical impedance measurements to detect and discriminate between individual bacterial spores on the basis of their electrical response. Using lithographically defined microelectrodes, we use dielectrophoresis to manipulate individual bacterial spores between the electrodes. The introduction of a single spore between the microelectrodes produces a significant change in electrical response that is species-dependent. When positioned between two electrodes and an AC voltage was applied, single spores caused current increases averaging 6.8 (+/-2.4) pA for Bacillus mycoides to 1.18 (+/-0.37) pA for Bacillus licheniformis. Using a mixture of spores of two different species, we demonstrate the ability to distinguish the species of individual spores in real time. This work demonstrates the feasibility of using impedance measurements for real-time detection and discrimination between different types of spores.

Chemoselective nanowire fuses: chemically induced cleavage and electrical detection of carbon nanofiber bridges.

A new type of nanoscale bioswitch based on the electrical detection of chemically induced cleavage of chemical bonds, which bind individual nanowires across a pair of electrodes is demonstrated. Carbon nanofibers are manipulated using dielectrophoresis to form single-nanowire bridges across microelectrode junctions, and are anchored through a biomolecular interaction. Once in place, chemically induced cleavage of a recognition site along the bonds linking the nanowire to the electrodes allows the nanowire to be easily removed by a flow of fluid; this removal can be detected in real time via changes in the AC electrical response. This form of sensing is inherently digital in nature as the removal of a single nanowire produces a sudden decrease in the current between electrodes and is essentially a chemoselective fuse. These results suggest that this sensing principle could be a general method for digital chemical and/or biological sensing using individual nanowires.

Dielectrophoretic manipulation and real-time electrical detection of single-nanowire bridges in aqueous saline solutions.

Dielectrophoretic manipulation of nanoscale materials is typically performed in nonionic, highly insulating solvents. However, biomolecular recognition processes, such as DNA hybridization and protein binding, typically operate in highly conducting, aqueous saline solutions. Here, we report investigations of the manipulation and real-time detection of individual nanowires bridging microelectrode gaps in saline solutions. Measurements of the electrode impedance versus frequency show a crossover in behavior at a critical frequency that is dependent on the ionic strength. We demonstrate that by operating above this critical frequency, it is possible to use dielectrophoresis to manipulate nanowires across electrode gaps in saline solutions. By using electrical ground planes and nulling schemes to reduce the background currents, we further demonstrate the ability to electrically detect bridging and unbridging events of individual nanowires in saline solutions. The ability to both manipulate and detect bridging events with electrical signals provides a pathway toward automated assembly of nanoscale devices that incorporate biomolecular recognition elements.

Critical oxide thickness for efficient single-walled carbon nanotube growth on silicon using thin SiO2 diffusion barriers.

The ability to integrate carbon nanotubes, especially single-walled carbon nanotubes, seamlessly onto silicon would expand their range of applications considerably. Though direct integration using chemical vapor deposition is the simplest method, the growth of single-walled carbon nanotubes on bare silicon and on ultrathin oxides is greatly inhibited due to the formation of a noncatalytic silicide. Using X-ray photoelectron spectroscopy, we show that silicide formation occurs on ultrathin oxides due to thermally activated metal diffusion through the oxide. Silicides affect the growth of single-walled nanotubes more than multi-walled nanotubes due to the increased kinetics at the higher single-walled nanotube growth temperature. We demonstrate that nickel and iron catalysts, when deposited on clean silicon or ultrathin silicon dioxide layers, begin to form silicides at relatively low temperatures, and that by 900 degrees C, all of the catalyst has been incorporated into the silicide, rendering it inactive for subsequent single-walled nanotube growth. We further show that a 4-nm silicon dioxide layer is the minimum diffusion barrier thickness that allows for efficient single-walled nanotube growth.

Effect of ozone oxidation on single-walled carbon nanotubes.

Exposing single-walled carbon nanotubes to room-temperature UV-generated ozone leads to an irreversible increase in their electrical resistance. We demonstrate that the increased resistance is due to ozone oxidation on the sidewalls of the nanotubes rather than at the end caps. Raman and X-ray photoelectron spectroscopies show an increase in the defect density due to the oxidation of the nanotubes. Using ultraviolet photoelectron spectroscopy, we show that these defects represent the removal of pi-conjugated electron states near the Fermi level, leading to the observed increase in electrical resistance. Oxidation of carbon nanotubes is an important first step in many chemical functionalization processes. Because the oxidation rate can be controlled with short exposures, UV-generated ozone offers the potential for use as a low-thermal-budget processing tool.

Outcomes following combined intramedullary nail and plate fixation for complex tibia fractures: A multi-centre study.

INTRODUCTION: Concomitant plate fixation as an adjunct to intramedullary nailing (IMN) of proximal third tibia fractures is a proven technique. Benefits include its role as a minimally invasive reduction aid, allowing for minimal soft tissue disruption. Expanding its indications as adjunct fixation to IMN throughout the tibia, we aimed to study outcomes in a multi-centre initiative. MATERIALS AND METHODS: From May 1999 to March 2010, a total of 1302 operatively treated tibial fractures (including plateau and pilon fractures) with complete medical records were identified for review. Of these, 376 cases were treated via IMN, of which 30 cases were treated via combined IMN and plating, meeting inclusion criteria. Primary outcome was union rates, time to union, and complication rates. Secondary outcomes included mean alignment from the immediate postoperative period to the time of final follow-up. RESULTS: Twenty-seven out of 30 patients were available for follow-up. Twenty-five (93%) achieved bony union; the remaining two patients, sustained Type IIIA and B injuries respectively, went onto non-union secondary to deep infection and required multiple re-operations before achieving ultimate union. Mean time at final follow-up was 20 ± 10 months, 96% were ambulatory at full weight bearing status with no malunions. No significant changes in alignment in either the coronal or sagittal planes were noted at time of final follow-up. CONCLUSION: Combined IMN and plate fixation is a reliable tool not only in the treatment of fractures of the proximal tibia, but also for those fractures in the diaphysis and segmental fractures with proximal and/or distal metadiaphyseal extension with consistent ability to maintain high union rates and maintained alignment. However, longer-term follow-up and prospective trials will be necessary before coming to a definitive conclusion.

In-plane contributions to phase contrast in intermittent contact atomic force microscopy.

Contrast in the phase response of intermittent-contact atomic force microscopy (IC-AFM) reveals in-plane structural and mechanical properties of polymer monolayers. This result is unexpected, as IC-AFM has previously only been considered as a probe of out-of-plane properties. Until now, AFM measurements of nanoscale in-plane properties have employed contact mode techniques. In-plane property measurements are possible with intermittent contact AFM because there is a small but significant component of tip motion parallel to the sample surface. This in-plane component of tip displacement is virtually universal in AFM, implying that oscillating-tip techniques generally are sensitive to in-plane material properties. We present a simple Hertzian model of intermittent-contact AFM that includes such an in-plane displacement.

Computer-assisted anterior cruciate ligament (ACL) reconstruction: the US perspective.

Computer-assisted anterior cruciate ligament (ACL) reconstruction in the United States has been used to help improve clinical outcomes and investigate tunnel placement and kinematic activity. Computer-assisted techniques were developed to improve accuracy of tunnel placement, because of concerns about the accuracy of manual tunnel placement causing revisions. Several authors have demonstrated improved tunnel location with computer assistance, although others have demonstrated little or no difference. More recently, American investigators have used computer assistance to evaluate the position and biomechanical behavior and kinematics of theoretical tunnel placement and also to assess in vitro and in vivo knee stability following ligament reconstruction. Computer assistance of anterior ligament reconstruction has demonstrated its value as a research and clinical tool in the United States.

Is there a role for intramedullary nails in the treatment of simple pilon fractures? Rationale and preliminary results.

INTRODUCTION: Certain patients with pilon fractures present with significant soft-tissue swelling or with a poor soft-tissue envelope typically not amenable to definitive fixation in the early time period. The objective of this study was to review the treatment of simple intra-articular fractures of the tibial plafond (Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association (AO/OTA) type 43C1-C2) via intramedullary nailing (IMN) with the assessment of clinical and radiographic results and any associated complications. MATERIALS AND METHODS: Retrospective clinical and radiological reviews of 31 patients sustaining AO/OTA type 43C distal tibial fractures treated with IMN were evaluated. Our main outcome measurement included achievable alignment in the immediate postoperative period and at the time of union along with complications or need for secondary procedures within the first year of follow-up. RESULTS: Seven patients were lost to follow-up. All the remaining patients achieved bony union at a mean union time of 14.1 ± 4.9 weeks with no evidence of malunion or malrotation. All patients were at full-weight-bearing status at 1-year follow-up. Complications were notable for one delayed union, one non-union, one patient with superficial wound drainage, two with deep infection, one with symptomatic hardware and one with deep vein thrombosis. CONCLUSION: Simple articular fractures of the tibial plafond (AO/OTA type 43C) treated via IMN can achieve excellent alignment and union rates with proper patient selection and surgical indication. One should not hesitate to use additional bone screws or plating options to help achieve better anatomic reduction. However, larger, prospective randomised trials comparing plating versus nailing, in experienced hands, are needed to completely delineate the utility of this treatment modality.

Covalent photochemical functionalization of amorphous carbon thin films for integrated real-time biosensing.

Recent studies have demonstrated that carbon, in the form of diamond, can be functionalized with molecular and/or biomolecular species to yield interfaces exhibiting extremely high stability and selectivity in binding to target biomolecules in solution. However, diamond and most other crystalline forms of carbon involve high-temperature deposition or processing steps that restrict their ability to be integrated with other materials. Here, we demonstrate that photochemical functionalization of amorphous carbon films followed by covalent immobilization of DNA yields highly stable surfaces with excellent biomolecular recognition properties that can be used for real-time biological detection. Carbon films deposited onto substrates at 300 K were functionalized with organic alkenes bearing protected amine groups and characterized using X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The functionalized carbon surfaces were covalently linked to DNA oligonucleotides. Measurements show very high selectivity for binding to the complementary sequence, and a high density of hybridizing DNA molecules. Samples repeatedly hybridized and denatured 25 times showed no significant degradation. The ability to use amorphous carbon films as a basis for real-time biosensing is demonstrated by coating quartz crystal microbalance (QCM) crystals with a thin carbon film and using this for covalent modification with DNA. Measurements of the resonance frequency show the ability to detect DNA hybridization in real time with a detection limit of <3% of a monolayer, with a high degree of reversibility. These results demonstrate that functionalized films of amorphous carbon can be used as a chemically stable platform for integrated biosensing using only room-temperature processing steps.

Manipulation and real-time electrical detection of individual bacterial cells at electrode junctions: a model for assembly of nanoscale biosystems.

Biological cells are complex objects that have the potential to act as templates for the subsequent construction of nanoscale structures. We demonstrate the ability to controllably and reversibly manipulate individual, live bacterial cells across micron-sized electrical gaps, and to detect bridging directly through changes in the electrical response. Our model system, Bacillus mycoides, is a rod-shaped bacterium approximately 800 nm wide and 5 microm long, similar in size and shape to many inorganic nanowires.

Material anisotropy revealed by phase contrast in intermittent contact atomic force microscopy.

Phase contrast in intermittent-contact atomic force microscopy (AFM) reveals in-plane structural and mechanical properties of polymer monolayers. This is surprising, because measurements of nanoscale in-plane properties typically require contact mode microscopies. Our measurements are possible because the tip oscillates not just perpendicular but also parallel to the sample surface along the long axis of the cantilever. This lateral tip displacement is virtually universal in AFM, implying that any oscillating-tip AFM technique is sensitive to in-plane material properties.