7,736 research outputs found
Systemic movement of FT mRNA and a possible role in floral induction
No full textFLOWERING LOCUS T (FT) protein is known to be part of the mobile flowering inducing “florigen” signal in plants, but it may not be acting alone. This article reviews the data that FT mRNA can also move systemically throughout the plant and into the shoot apical meristem (SAM) independently of the FT protein. There is a promotion of flowering when increased levels of virally expressed FT mRNA are present together with endogenously produced FT protein in inducing conditions, even if the additional FT mRNA is non-translatable and thus not increasing the overall levels of FT protein. A specific sequence, or “zip code” of the FT mRNA is required for systemic movement and this sequence binds a specific protein(s) in plant extracts. This raises the possibility the FT mRNA may be moving systemically through the plant and into the SAM as an RNA–protein complex, whether FT protein is also a component of this mobile complex remains to be determined
FT-infrared spectroscopic studies of lymphoma, lymphoid and myeloid leukaemia cell lines
No full textThis paper presents a novel method to characterise spectral differences that
distinguish leukaemia and lymphoma cell lines. This is based on objective
spectral measurements of major cellular biochemical constituents and
multivariate spectral processing. Fourier transform infrared (FT-IR) maps of the
lymphoma, lymphoid and myeloid leukaemia cell samples were obtained using a
Perkin-Elmer Spotlight 300 FT-IR imaging spectrometer. Multivariate statistical
techniques incorporating principal component analysis (PCA) and linear
discriminant analysis (LDA) were used to construct a mathematical model. This
model was validated for reproducibility. Multivariate statistical analysis of
FTIR spectra collected for each cell sample permit a combination of unsupervised
and supervised methods of distinguishing cell line types. This resulted in the
clustering of cell line populations, indicating distinct bio-molecular
differences. Major spectral differences were observed in the 4000 to 800 cm-
1 spectral region. Bands in the averaged spectra for the cell line were assigned
to the major biochemical constituents including; proteins, fatty acids,
carbohydrates and nucleic acids. The combination of FT-IR spectroscopy and
multivariate statistical analysis provides an important insight into the
fundamental spectral differences between the cell lines, which differ according
to the cellular biochemical composition. These spectral differences can serve as
potential biomarkers for the differentiation of leukaemia and lymphoma cells.
Consequently these differences could be used as the basis for developing a
spectral method for the detection and identification of haematological
malignancies
Resistive inspiratory muscle training in sleep disordered breathing of traumatic tetraplegia.
No full textResistive inspiratory muscle training in sleep disordered breathing of traumatic tetraplegia
No full textClinical experience with intra-aortic balloon counterpulsation over 10 years: A retrospective cohort study of 459 patients.
No full textInvestigating the potential use of virus technology to further our understanding of floral induction and its application in plant breeding programmes
No full textFlowering Locus T (FT ) plays a pivotal role in floral induction. It integrates the inputs from a complex network of flowering signalling pathways. Flowering is an efficiently orchestrated event that occurs in a plant at a particular time to ensure maximum reproductive success. It has been suggested that the FT protein is a long- distance mobile floral stimulus. In this report studies with a mutant version of FT (mFT) which had the start codon replaced with a stop codon to generate a non-translatable FT indicated that the mRNA was also capable of long distance movement although its physiological function as a floral stimulus was inhibited.
Gene function study of FT and FT orthologues on brassica, tobacco, tomato and potato using the plant virus expression vector Potato Virus X (PVX) generated some interesting findings. In Short day Maryland Mammoth tobacco plants the overexpression of the Arabidopsis FT under non-inductive Long day condition induced early flowering while the mFT and mock control remained in the vegetative stage. In short day potato, it did not seem to have an effect on tuberization as only one from five of the inoculated plants tuberized. In brassica (broccoli) the effect on flowering time was inhibited due to Virus-induced Gene Silencing (VIGS) but the tomato FT (SP6A) had an effect on flowering time.
In tomato, the overexpression of the Arabidopsis FT and FT- orthologues from tomato induced early flowering but the difference in flowering time in comparison to the controls was only a few days. Phenotypical and morphological changes such as seed production and lateral side shoot development were caused by expression of the target genes. The exact mechanism of action of these genes in the control of seed production and lateral side shoot development is unclear
Advanced electronics for fourier-transform ion cyclotron resonance mass spectrometry
No full textWith the development of mass spectrometry (MS) instruments starting in the
late 19th century, more and more research emphasis has been put on MS related
subjects, especially the instrumentation and its applications. Instrumentation
research has led modern mass spectrometers into a new era where the MS performance,
such as resolving power and mass accuracy, is close to its theoretical
limit. Such advanced performance releases more opportunities for scientists to
conduct analytical research that could not be performed before.
This thesis reviews general MS history and some of the important milestones,
followed by introductions to ion cyclotron resonance (ICR) technique
and quadrupole operation. Existing electronic designs, such as Fourier-transform
ion cyclotron resonance (FT-ICR) preamplifiers (for ion signal detection) and
radio-frequency (RF) oscillators (for ion transportation/filtering) are reviewed.
Then the potential scope for improvement is discussed.
Two new FT-ICR preamplifiers are reported; both preamplifiers operate at
room temperature. The first preamplifier uses an operational amplifier (op amp)
in a transimpedance configuration. When a 18-k
feedback resistor is used, this
preamplifier delivers a transimpedance of about 85 dB
, and an input current
noise spectral density of around 1 pA/
p
Hz. The total power consumption of
this circuit is around 310 mW when tested on the bench. This preamplifier has a
bandwidth of fi3 kHz to 10 MHz, which corresponds to the mass-to-charge ratio,
m/z, of approximately 18 to 61k at 12 T for FT-ICR MS. The transimpedance
and the bandwidth can be adjusted by replacing passive components such as the
feedback resistor and capacitor. The feedback and bandwidth limitation of the
circuit is also discussed. When using an 0402 type surface mount resistor, the
maximum possible transimpedance, without sacrificing its bandwidth, is approximated
to 5.3 M
. Under this condition, the preamplifier is estimated to be able
to detect ~110 charges.
The second preamplifier employs a single-transistor design using a different
feedback arrangement, a T-shaped feedback network. Such a feedback system
allows ~100-fold less feedback resistance at a given transimpedance, hence preserving
bandwidth, which is beneficial to applications demanding high gain. The
single-transistor preamplifier yields a low power consumption of ~5.7 mW, and
a transimpedance of 80 dB
in the frequency range between 1 kHz and 1 MHz
(m/z of around 180 to 180k for a 12-T FT-ICR system). In trading noise performance
for higher transimpedance, an alternative preamplifier design has also
been presented with a transimpedance of 120 dB
in the same frequency range.
The previously reported room-temperature FT-ICR preamplifier had a voltage gain of about 25, a bandwidth of around 1 MHz when bench tested, and
a voltage noise spectral density of ~7.4 nV/
p
Hz. The bandwidth performance
when connecting this preamplifier to an ICR cell has not been reported. However,
from the transimpedance theory, the transimpedance preamplifiers reported in
this work will have a bandwidth wider by a factor of the open-loop gain of the
amplifier.
In a separate development, an oscillator is proposed as a power supply for
a quadrupole mass filter in a mass spectrometer system. It targets a stabilized
output frequency, and a feedback control for output amplitude stabilization. The
newly designed circuit has a very stable output frequency at 1 MHz, with a frequency
tolerance of 15 ppm specified by the crystal oscillator datasheet. Within
this circuit, an automatic gain control (AGC) unit is built for output amplitude
stabilisation. A new transformer design is also proposed. The dimension of the
quadrupole being used as a mass filter will be determined in the future. This
circuit (in particular the transformer and the quadrupole connection/mounting
device) will be finalised after the design of the quadrupole.
Finally, this thesis concludes with a discussion between the gain and the noise
performance of an FT-ICR preamplifier. A brief analysis about the correlation
between the gain, cyclotron frequency, and input capacitance is performed. Future
work is also suggested for extending this research
From Canon Road, 900 ft. above river, S.E. to Upper Falls (109 ft. high), Yellowstone Park, U.S.A.
No full textFrom Canon Road, 900 ft. above river, S.E. to Upper Falls (109 ft. high), Yellowstone Park, U.S.A
Evolution of Left Atrial Systolic and Diastolic Functions in Different Stages of Hypertension: Distinct Effects of Blood Pressure Control.
No full textRenin-angiotensin system gene polymorphisms and atrial fibrillation: A regression approach for the detection of gene-gene interactions in a large hospitalized population.
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