695 research outputs found
Catheters and Infections
Catheters are used for effective drainage of the bladder, either temporally or permanently,
in the presence of physiological and anatomical defects or obstruction of the lower urinary
tract. Catheters are used for a variety of reasons, as follows, to maintain bladder drainage
during and following surgery or epidurals anesthesia for minimizing and prevention of the
risk of distension injuries; investigations, for accurate urine output measurement, and
measurement of post-micturition residuals; treatments, to relieve urinary retention or for
chemotherapy instillation; intractable incontinence, as the final option for containment
Current Trends in Urinary Diversion in Men
Prior to the introduction of the ileal conduit more than four decades ago, the options for
urinary diversion after cystectomy were extremely limited. Direct cutaneous anastomoses of
the collecting system (cutaneous pyelostomies, ureterostomies) offered patients a short-term
diversion, but the benefits were outweighed by significant complications: recession or
stenosis of the stoma. The first choice of diversion was the ureterosigmoidostomy with or
without antireflux technique. Then it fell in popularity and was replaced with
continent/non-continent uretero-ileo-cutaneous diversions. Only in the last years the
continent orthotopic neobladder has been widely employed as first procedure choice. At
present, patients can be offered a non-continent cutaneous diversion, a continent cutaneous
diversion or an orthotopic neobladder urinary reconstructio
Time domain study of frequency-power correlation in spin-torque oscillators
This paper describes a numerical experiment, based on full micromagnetic
simulations of current-driven magnetization dynamics in nanoscale spin valves,
to identify the origins of spectral linewidth broadening in spin torque
oscillators. Our numerical results show two qualitatively different regimes of
magnetization dynamics at zero temperature: regular (single-mode precessional
dynamics) and chaotic. In the regular regime, the dependence of the oscillator
integrated power on frequency is linear, and consequently the dynamics is well
described by the analytical theory of current-driven magnetization dynamics for
moderate amplitudes of oscillations. We observe that for higher oscillator
amplitudes, the functional dependence of the oscillator integrated power as a
function of frequency is not a single-valued function and can be described
numerically via introduction of nonlinear oscillator power. For a range of
currents in the regular regime, the oscillator spectral linewidth is a linear
function of temperature. In the chaotic regime found at large current values,
the linewidth is not described by the analytical theory. In this regime we
observe the oscillator linewidth broadening, which originates from sudden jumps
of frequency of the oscillator arising from random domain wall nucleation and
propagation through the sample. This intermittent behavior is revealed through
a wavelet analysis that gives superior description of the frequency jumps
compared to several other techniques.Comment: 11 pages, 4 figures to appear in PR
Detection of LDDoS Attacks Based on TCP Connection Parameters
Low-rate application layer distributed denial of service (LDDoS) attacks are
both powerful and stealthy. They force vulnerable webservers to open all
available connections to the adversary, denying resources to real users.
Mitigation advice focuses on solutions that potentially degrade quality of
service for legitimate connections. Furthermore, without accurate detection
mechanisms, distributed attacks can bypass these defences. A methodology for
detection of LDDoS attacks, based on characteristics of malicious TCP flows, is
proposed within this paper. Research will be conducted using combinations of
two datasets: one generated from a simulated network, the other from the
publically available CIC DoS dataset. Both contain the attacks slowread,
slowheaders and slowbody, alongside legitimate web browsing. TCP flow features
are extracted from all connections. Experimentation was carried out using six
supervised AI algorithms to categorise attack from legitimate flows. Decision
trees and k-NN accurately classified up to 99.99% of flows, with exceptionally
low false positive and false negative rates, demonstrating the potential of AI
in LDDoS detection
Durability of a recombination catalyst-based membrane-electrode assembly for electrolysis operation at high current density
Hydrogen production through polymer electrolyte membrane water electrolysis was investigated at high current density (4 A cm-2). A PtCo recombination catalyst-based membrane-electrode assembly (MEA) was assessed in terms of performance, efficiency and durability. The electrolysis cell consisted of a thin (50 µm) perfluorosulfonic acid membrane and low platinum group metals (PGM) catalyst loadings (0.6 mgMEA PGM cm-2). An unsupported PtCo catalyst was successfully integrated in the anode. A composite catalytic layer made of IrRuOx and PtCo assisted both oxygen evolution and oxidation of hydrogen permeated through the membrane. The cell voltage for the recombination catalyst-based MEA was about 30 mV lower than the bare MEA during a 3500 h durability test. The modified MEA showed low performance losses during 3500 hours operation at high current density (4 A cm-2) with low catalyst loadings. A decay rate of 9 µV/h was observed in the last 1000 hours. These results are promising for decreasing the capital costs of polymer electrolyte membrane electrolysers. Moreover, the stable voltage efficiency of about 80% vs. the high heating value (HHV) of hydrogen at 4 A cm-2, here achieved, appears very promising to decrease operating expenditures
Enhanced performance of a PtCo recombination catalyst for reducing the H 2 concentration in the O 2 stream of a PEM electrolysis cell in the presence of a thin membrane and a high differential pressure
High electrochemical efficiency at elevated current densities and low H 2 concentration in
O 2 can be achieved in PEM electrolysis using thin membrane and integrated
recombination catalyst. An enhanced PtCo alloy recombination catalyst was synthesized
and used at the anode of a membrane-electrode assembly (MEA). This allowed reducing
the H 2 concentration in the oxygen stream during electrolysis operation with a thin 50 µm
perfluorosulfonic acid (PFSA) Aquivion
®
membrane. Both dual-layer and composite anode
configurations (PtCo/IrRuOx) were investigated. The electrochemical performance of the
MEAs containing the recombination catalyst was better than a bare MEA while producing a
decrease of the H 2 content at the anode. This allowed extending the partial load operation
down to 5% at 55°C under a differential pressure of 20 bar. The effects of the cathodic
pressure and cell temperature (including evaluation of intermediate temperature operation
at 140 °C) on both electrochemical performance and H 2 concentration in the anode stream
were investigated. An excellent performance of 4 A cm
-2
at 1.75 V, at 140 °C, 20 bar
cathode pressure, 5.5 bar anode pressure, with 0.6 mg cm
-2
overall precious metal
catalysts content was recorded. At 140 °C, the MEA also showed a moderate H 2
concentration in O 2 of about 2.3 %, almost constant through most of the current density
range
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