785 research outputs found
Shift of microbial communities and reduced enzymatic activity in soil under plastic mulching system in strawberry cultivation
The use of plastic mulching (PM) in agriculture has strongly increased in the last years. Improved water saving and higher soil temperature are some advantages of this management. Yet, an intensive use of PM has been recently linked to negative effects on soil quality. The aim of this study is thus to assess the effects of long-term plastic mulching (PM) on soil microbial indicators. PM was compared with the use of wheat straw mulching (SM), an also widely used mulch material. Samples were collected at two depths (0-5 and 5-10 cm) from strawberry fields, after 4-year management. Cultivation in PM and SM was done in a ridge-furrow system with subsurface irrigation. Soil characterization comprised soil texture and aggregate stability, soil organic carbon, pH and water content. Soil microbial analysis included: Soil microbial biomass (Cmic), a fraction of soil cultivable fungi (CFU values), soil bacteria (16S rRNA), denitrifying community (nirK, nirS, narG, napA genes), soil enzyme activity (C-Chitinase, P-Phosphatase and N Leucine-aminopeptidase), deoxynivalenol (DON) content and Cmic:Corg ratio. Positive effects on soil physicochemical properties were observed under PM as compared to SM, reflected by a higher soil carbon content and better aggregate stability (p>0.05). Yet, soil microbial analysis revealed some differences between managements. Cmic values were comparable in both systems, showing no differences in soil microbial biomass. In the same way, the analysis of functional genes of the N cycle and the activity of the enzymes P-Phosphatase and N Leucine-aminopeptidase was not affected by the mulching treatment. But, the abundance of bacteria (18%) and a fraction of soil cultivable fungi were reduced by respectively 18 and 62% under PM. Since the Cmic values remained similar between treatments, this accounts for a shift of microbial communities under PM. Additionally, C-Chitinase activity declined under PM. Interestingly, this enzyme correlated positively with CFU values (r=0.781, p=0.001), suggesting that a reduction of the activity is a consequence of the reduction of the fungal biomass. Additionally, a higher deoxynivalenol concentration (2.2 ± 2.4 µg kg-1) and a reduced Cmic:Corg ratio (1.3±0.3%) were observed under PM, indicative of less appropriate soil conditions after long-term PM management
One-Point Probability Distribution Functions of Supersonic Turbulent Flows in Self-Gravitating Media
Turbulence is essential for understanding the structure and dynamics of
molecular clouds and star-forming regions. There is a need for adequate tools
to describe and characterize the properties of turbulent flows. One-point
probability distribution functions (pdf's) of dynamical variables have been
suggested as appropriate statistical measures and applied to several observed
molecular clouds. However, the interpretation of these data requires comparison
with numerical simulations. To address this issue, SPH simulations of driven
and decaying, supersonic, turbulent flows with and without self-gravity are
presented. In addition, random Gaussian velocity fields are analyzed to
estimate the influence of variance effects. To characterize the flow
properties, the pdf's of the density, of the line-of-sight velocity centroids,
and of the line centroid increments are studied. This is supplemented by a
discussion of the dispersion and the kurtosis of the increment pdf's, as well
as the spatial distribution of velocity increments for small spatial lags. From
the comparison between different models of interstellar turbulence, it follows
that the inclusion of self-gravity leads to better agreement with the observed
pdf's in molecular clouds. The increment pdf's for small spatial lags become
exponential for all considered velocities. However, all the processes
considered here lead to non-Gaussian signatures, differences are only gradual,
and the analyzed pdf's are in addition projection dependent. It appears
therefore very difficult to distinguish between different physical processes on
the basis of pdf's only, which limits their applicability for adequately
characterizing interstellar turbulence.Comment: 38 pages (incl. 17 figures), accepted for publication in ApJ, also
available with full resolution figures at
http://www.strw.leidenuniv.nl/~klessen/Preprint
AAOmega radial velocities rule out current membership of the planetary nebula NGC 2438 in the open cluster M46
We present new radial velocity measurements of 586 stars in a one-degree
field centered on the open cluster M46, and the planetary nebula NGC 2438
located within a nuclear radius of the cluster. The data are based on
medium-resolution optical and near-infrared spectra taken with the AAOmega
spectrograph on the Anglo-Australian Telescope. We find a velocity difference
of about 30 km/s between the cluster and the nebula, thus removing all
ambiguities about the cluster membership of the planetary nebula caused by
contradicting results in the literature. The line-of-sight velocity dispersion
of the cluster is 3.9+/-0.3 km/s, likely to be affected by a significant
population of binary stars.Comment: 6 pages + 5 figures, accepted for publication in MNRA
Epidemiology and Outcomes of Vertebral Artery Injury in 16 582 Cervical Spine Surgery Patients: An AOSpine North America Multicenter Study.
STUDY DESIGN: A multicenter retrospective case series was compiled involving 21 medical institutions. Inclusion criteria included patients who underwent cervical spine surgery between 2005 and 2011 and who sustained a vertebral artery injury (VAI).
OBJECTIVE: To report the frequency, risk factors, outcomes, and management goals of VAI in patients who have undergone cervical spine surgery.
METHODS: Patients were evaluated on the basis of condition-specific functional status using the Neck Disability Index (NDI), modified Japanese Orthopaedic Association (mJOA) score, the Nurick scale, and the 36-Item Short-Form Health Survey (SF-36).
RESULTS: VAIs were identified in a total of 14 of 16 582 patients screened (8.4 per 10 000). The mean age of patients with VAI was 59 years (±10) with a female predominance (78.6%). Patient diagnoses included myelopathy, radiculopathy, cervical instability, and metastatic disease. VAI was associated with substantial blood loss (770 mL), although only 3 cases required transfusion. Of the 14 cases, 7 occurred with an anterior-only approach, 3 cases with posterior-only approach, and 4 during circumferential approach. Fifty percent of cases of VAI with available preoperative imaging revealed anomalous vessel anatomy during postoperative review. Average length of hospital stay was 10 days (±8). Notably, 13 of the 14 (92.86%) cases resolved without residual deficits. Compared to preoperative baseline NDI, Nurick, mJOA, and SF-36 scores for these patients, there were no observed changes after surgery (P = .20-.94).
CONCLUSIONS: Vertebral artery injuries are potentially catastrophic complications that can be sustained from anterior or posterior cervical spine approaches. The data from this study suggest that with proper steps to ensure hemostasis, patients recover function at a high rate and do not exhibit residual deficits
Chemical Addressability of Ultraviolet-Inactivated Viral Nanoparticles (VNPs)
. Thus, inactivation of the virus RNA genome is important for biosafety considerations, however the surface characteristics and chemical reactivity of the particles must be maintained in order to preserve chemical and structural functionality. were shown to maintain particle structure and chemical reactivity, and cellular binding properties were similar to CPMV-WT. applications
Men's Experiences of the UK Criminal Justice System Following Female-Perpetrated Intimate Partner Violence
© 2015 Springer Science+Business Media New York The current study aimed to explore men’s experience of the UK Criminal Justice System (CJS) following female-perpetrated intimate partner violence (IPV). Unstructured face-to-face and Skype interviews were conducted with six men aged between 40–65 years. Interviews were transcribed and analysed using interpretative phenomenological analysis (IPA). Due to the method of analysis and the sensitive nature of the research, the researcher engaged in a process of reflexivity. Four main themes were identified, including ‘Guilty until Proven Innocent: Victim Cast as Perpetrator;’ ‘Masculine Identity;’ ‘Psychological Impact’ and ‘Light at the End of the Tunnel.’ Themes were discussed and illustrated with direct quotes drawn from the transcripts. Directions for future research, criminal justice interventions, and therapeutic interventions were discussed
Kinetic Energy Decay Rates of Supersonic and Super-Alfvenic Turbulence in Star-Forming Clouds
We present numerical studies of compressible, decaying turbulence, with and
without magnetic fields, with initial rms Alfven and Mach numbers ranging up to
five, and apply the results to the question of the support of star-forming
interstellar clouds of molecular gas. We find that, in 1D, magnetized
turbulence actually decays faster than unmagnetized turbulence. In all the
regimes that we have studied 3D turbulence-super-Alfvenic, supersonic,
sub-Alfvenic, and subsonic-the kinetic energy decays as (t-t0)^(-x), with 0.85
< x < 1.2. We compared results from two entirely different algorithms in the
unmagnetized case, and have performed extensive resolution studies in all
cases, reaching resolutions of 256^3 zones or 350,000 particles. We conclude
that the observed long lifetimes and supersonic motions in molecular clouds
must be due to external driving, as undriven turbulence decays far too fast to
explain the observations.Comment: Submitted to Phys. Rev. Letters, 29 Nov. 1997. 10 pages, 2 figures,
also available from http://www.mpia-hd.mpg.de/theory/preprints.html#maclo
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