3 research outputs found
Data_Sheet_1_Characteristics of soil microbiota and organic carbon distribution in jackfruit plantation under different fertilization regimes.docx
Manure amendment to improve soil organic carbon (SOC) content is an important strategy to sustain ecosystem health and crop production. Here, we utilize an 8-year field experiment to evaluate the impacts of organic and chemical fertilizers on SOC and its labile fractions as well as soil microbial and nematode communities in different soil depths of jackfruit (Artocarpus heterophyllus Lam.). Three treatments were designed in this study, including control with no amendment (CK), organic manure (OM), and chemical fertilizer (CF). Results showed that OM significantly increased the abundance of total nematodes, bacterivores, bacteria, and fungi as well as the value of nematode channel ratio (NCR) and maturity index (MI), but decreased plant-parasites and Shannon diversity (H′). Soil microbial and nematode communities in three soil depths were significantly altered by fertilizer application. Acidobacteria and Chloroflexi dominated the bacterial communities of OM soil, while Nitrospira was more prevalent in CF treatment. Organic manure application stimulated some functional groups of the bacterial community related to the C cycle and saprotroph-symbiotroph fungi, while some groups related to the nitrogen cycle, pathotroph-saprotroph-symbiotroph and pathotroph-saprotroph fungi were predominated in CF treatment. Furthermore, OM enhanced the soil pH, contents of total soil N, P, K, and SOC components, as well as jackfruit yield. Chemical fertilizers significantly affected available N, P, and K contents. The results of network analyses show that more significant co-occurrence relationships between SOC components and nematode feeding groups were found in CK and CF treatments. In contrast, SOC components were more related to microbial communities than to nematode in OM soils. Partial least-squares-path modeling (PLS-PM) revealed that fertilization had significant effects on jackfruit yield, which was composed of positive direct (73.6%) and indirect effects (fertilization → fungal community → yield). It was found that the long-term manure application strategy improves soil quality by increasing SOM, pH, and nutrient contents, and the increased microbivorous nematodes abundance enhanced the grazing pressure on microorganisms and concurrently promoted microbial-derived SOC turnover.</p
Low Thermal Boundary Resistance Interfaces for GaN-on-Diamond Devices
The development of
GaN-on-diamond devices holds much promise for the creation of high-power
density electronics. Inherent to the growth of these devices, a dielectric
layer is placed between the GaN and diamond, which can contribute
significantly to the overall thermal resistance of the structure.
In this work, we explore the role of different interfaces in contributing
to the thermal resistance of the interface of GaN/diamond layers,
specifically using 5 nm layers of AlN, SiN, or no interlayer at all.
Using time-domain thermoreflectance along with electron energy loss
spectroscopy, we were able to determine that a SiN interfacial layer
provided the lowest thermal boundary resistance (<10 m<sup>2</sup>K/GW) because of the formation of an Si–C–N layer at
the interface. The AlN and no interlayer samples were observed to
have TBRs greater than 20 m<sup>2</sup>K/GW as a result of a harsh
growth environment that roughened the interface (enhancing phonon
scattering) when the GaN was not properly protected
Direct Visualization of Thermal Conductivity Suppression Due to Enhanced Phonon Scattering Near Individual Grain Boundaries
Understanding
the impact of lattice imperfections on nanoscale
thermal transport is crucial for diverse applications ranging from
thermal management to energy conversion. Grain boundaries (GBs) are
ubiquitous defects in polycrystalline materials, which scatter phonons
and reduce thermal conductivity (κ). Historically, their impact
on heat conduction has been studied indirectly through spatially averaged
measurements, that provide little information about phonon transport
near a single GB. Here, using spatially resolved time-domain thermoreflectance
(TDTR) measurements in combination with electron backscatter diffraction
(EBSD), we make localized measurements of κ within few μm
of individual GBs in boron-doped polycrystalline diamond. We observe
strongly suppressed thermal transport near GBs, a reduction in κ
from ∼1000 W m<sup>–1</sup> K<sup>–1</sup> at
the center of large grains to ∼400 W m<sup>–1</sup> K<sup>–1</sup> in the immediate vicinity of GBs. Furthermore, we
show that this reduction in κ is measured up to ∼10 μm
away from a GB. A theoretical model is proposed that captures the
local reduction in phonon mean-free-paths due to strongly diffuse
phonon scattering at the disordered grain boundaries. Our results
provide a new framework for understanding phonon–defect interactions
in nanomaterials, with implications for the use of high-κ polycrystalline
materials as heat sinks in electronics thermal management