702 research outputs found
Opioid-Free Anesthesia for Open Radical Cystectomy Is Feasible and Accelerates Return of Bowel Function: A Matched Cohort Study.
The aim of this study was to evaluate the feasibility of opioid-free anesthesia (OFA) in open radical cystectomy (ORC) with urinary diversion and to assess the impact on recovery of gastrointestinal function. We hypothesized that OFA would lead to earlier recovery of bowel function. A total of 44 patients who underwent standardized ORC were divided into two groups (OFA group vs. control group). In both groups, patients received epidural analgesia (OFA group: bupivacaine 0.25%, control group: bupivacaine 0.1%, fentanyl 2 mcg/mL, and epinephrine 2 mcg/mL). The primary endpoint was time to first defecation. Secondary endpoints were incidence of postoperative ileus (POI) and incidence of postoperative nausea and vomiting (PONV). The median time to first defecation was 62.5 h [45.8-80.8] in the OFA group and 118.5 h [82.6-142.3] (p < 0.001) in the control group. With regard to POI (OFA group: 1/22 patients (4.5%); control group: 2/22 (9.1%)) and PONV (OFA group: 5/22 patients (22.7%); control group: 10/22 (45.5%)), trends but no significant results were found (p = 0.99 and p = 0.203, respectively). OFA appears to be feasible in ORC and to improve postoperative functional gastrointestinal recovery by halving the time to first defecation compared with standard fentanyl-based intraoperative anesthesia
Determination of Ketamine and Norketamine in hair samples using MEPS as sample clean-up
Palestra realizada no encontro SoHT-GTFI Joint Meeting, Verona, Junho 2022Introduction and Aim: The use of hair samples to determine ketamine (K) and its metabolite, norketamine (NK), has been studied by several authors, using different clean-up approaches. However, microextraction by packed sorbent (MEPS), a miniaturized form of the classic solid-phase extraction has not been applied to date for the purpose. Therefore, a method to determine K and NK in hair samples was developed, optimized, and validated using MEPS as sample clean-up.
Materials & Methods: Hair samples were scissor-cut into small fragments, and rinsed with methanol to remove dirt and externally deposited material. Following an overnight incubation with methanol at 65 ºC (no stirring), the compounds were analysed by GC-MS/MS without the need of derivatization procedures; MEPS conditions were: conditioning (5 x 250 µL of methanol and 4 x 250 µL of deionized water); load (10 x 150 µL of hair extract); washing (50 µL of 0.1% acetic acid and 50 µL of 10% methanol); and elution (100 µL of 3% ammonium hydroxide in methanol).
Results & Discussion: The procedure resulted in acceptable recoveries, 39-61% for K and 32-43% for NK, and allowed reaching limits of quantification (LOQs) of 50 pg/mg for both analytes. The analytical method presented acceptable accuracy and precision with coefficients of variation typically lower than 15% and BIAS within ± 15%, except at the LOQ (20%). The method was successfully applied to 2 authentic samples, and ketamine concentrations were below 0.05 and 0.18 ng/mg. Norketamine was not detected.
Conclusions: This work is the first analytical method using MEPS coupled to GC-MS/MS for the determination of K and NK in hair samples. Following a comparison with a SPE-based method using authentic samples, it was considered rapid and suitable for routine analysis.
Acknowledgments: FCT (UIDB /00709/2020 and UIDP/00709/2020). A.Y. Simão acknowledges the PhD fellowship from FCT (2020.09070.BD).N/
Conformal mapping and shot noise in graphene
Ballistic transport through a collection of quantum billiards in undoped
graphene is studied analytically within the conformal mapping technique. The
billiards show pseudodiffusive behavior, with the conductance equal to that of
a classical conductor characterized by the conductivity ,
and the Fano factor . By shrinking at least one of the billiard
openings, we observe a tunneling behavior, where the conductance shows a
power-law decay with the system size, and the shot noise is Poissonian (F=1).
In the crossover region between tunneling and pseudodiffusive regimes, the
conductance . The degeneracy for the Corbino
disk, which preserves the full symmetry of the Dirac equation, for
billiards bounded with smooth edges which break the symplectic symmetry, and
when abrupt edges lead to strong intervalley scattering. An alternative,
analytical or numerical technique, is utilized for each of the billiards to
confirm the applicability of the conformal mapping for various boundary
conditions.Comment: RevTeX, 16 pages, 15 figure
Fluctuations of an Atomic Ledge Bordering a Crystalline Facet
When a high symmetry facet joins the rounded part of a crystal, the step line
density vanishes as sqrt(r) with r denoting the distance from the facet edge.
This means that the ledge bordering the facet has a lot of space to meander as
caused by thermal activation. We investigate the statistical properties of the
border ledge fluctuations. In the scaling regime they turn out to be
non-Gaussian and related to the edge statistics of GUE multi-matrix models.Comment: Version with major revisions -- RevTeX, 4 pages, 2 figure
Ground state of the random-bond spin-1 Heisenberg chain
Stochastic series expansion quantum Monte Carlo is used to study the ground
state of the antiferromagnetic spin-1 Heisenberg chain with bond disorder.
Typical spin- and string-correlations functions behave in accordance with
real-space renormalization group predictions for the random-singlet phase. The
average string-correlation function decays algebraically with an exponent of
-0.378(6), in very good agreement with the prediction of , while the average spin-correlation function is found to decay with an
exponent of about -1, quite different from the expected value of -2. By
implementing the concept of directed loops for the spin-1 chain we show that
autocorrelation times can be reduced by up to two orders of magnitude.Comment: 9 pages, 10 figure
Origin for the enhanced copper spin echo decay rate in the pseudogap regime of the multilayer high-T_c cuprates
We report measurements of the anisotropy of the spin echo decay for the inner
layer Cu site of the triple layer cuprate, Hg_0.8Re_0.2Ba_2Ca_2Cu_3O_8 (T_c=126
K) in the pseudogap T regime below T_pg ~ 170 K and the corresponding analysis
for their interpretation. As the field alignment is varied, the shape of the
decay curve changes from Gaussian (H_0 \parallel c) to single exponential (H_0
\perp c). The latter characterizes the decay caused by the fluctuations of
adjacent Cu nuclear spins caused by their interactions with electron spins. The
angular dependence of the second moment (T_{2M}^{-2} \equiv )
deduced from the decay curves indicates that T_{2M}^{-2} for H_0 \parallel c,
which is identical to T_{2G}^{-2} (T_{2G} is the Gaussian component), is
substantially enhanced, as seen in the pseudogap regime of the bilayer systems.
Comparison of T_{2M}^{-2} between H_0 \parallel c and H_0 \perp c indicates
that this enhancement is caused by electron spin correlations between the inner
and the outer CuO_2 layers. These results provide the answer to the
long-standing controversy regarding the opposite T dependences of (T_1T)^{-1}
and T_{2G}^{-2} in the pseudogap regime of bi- and trilayer systems.Comment: 4 pages, 4 figure
A Two-dimensional Infinte System Density Matrix Renormalization Group Algorithm
It has proved difficult to extend the density matrix renormalization group
technique to large two-dimensional systems. In this Communication I present a
novel approach where the calculation is done directly in two dimensions. This
makes it possible to use an infinite system method, and for the first time the
fixed point in two dimensions is studied. By analyzing several related blocking
schemes I find that there exists an algorithm for which the local energy
decreases monotonically as the system size increases, thereby showing the
potential feasibility of this method.Comment: 5 pages, 6 figure
Information Loss in Coarse Graining of Polymer Configurations via Contact Matrices
Contact matrices provide a coarse grained description of the configuration
omega of a linear chain (polymer or random walk) on Z^n: C_{ij}(omega)=1 when
the distance between the position of the i-th and j-th step are less than or
equal to some distance "a" and C_{ij}(omega)=0 otherwise. We consider models in
which polymers of length N have weights corresponding to simple and
self-avoiding random walks, SRW and SAW, with "a" the minimal permissible
distance. We prove that to leading order in N, the number of matrices equals
the number of walks for SRW, but not for SAW. The coarse grained Shannon
entropies for SRW agree with the fine grained ones for n <= 2, but differs for
n >= 3.Comment: 18 pages, 2 figures, latex2e Main change: the introduction is
rewritten in a less formal way with the main results explained in simple
term
Quantum Dot as Spin Filter and Spin Memory
We consider a quantum dot in the Coulomb blockade regime weakly coupled to
current leads and show that in the presence of a magnetic field the dot acts as
an efficient spin-filter (at the single-spin level) which produces a
spin-polarized current. Conversely, if the leads are fully spin-polarized the
up or down state of the spin on the dot results in a large sequential or small
cotunneling current, and thus, together with ESR techniques, the setup can be
operated as a single-spin memory.Comment: 4 pages, 3 figures, REVTe
The Determination of Cannabinoids in Urine Samples Using Microextraction by Packed Sorbent and Gas Chromatography-Mass Spectrometry
Cannabis is the most consumed illicit drug worldwide, and its legal status is a source of concern. This study proposes a rapid procedure for the simultaneous quantification of Δ9-tetrahydrocannabinol (THC), 11-hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC), 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH), cannabidiol (CBD), and cannabinol (CBN) in urine samples. Microextraction by packed sorbent (MEPS) was used to pre-concentrate the analytes, which were detected by gas chromatography–mass spectrometry. The procedure was previously optimized, and the final conditions were: conditioning with 50 µL methanol and 50 µL of water, sample load with two draw–eject cycles, and washing with 310 µL of 0.1% formic acid in water with 5% isopropanol; the elution was made with 35 µL of 0.1% ammonium hydroxide in methanol. This fast extraction procedure allowed quantification in the ranges of 1–400 ng/mL for THC and CBD, 5–400 ng/mL for CBN and 11-OH-THC, and 10–400 ng/mL for THC-COOH with coefficients of determination higher than 0.99. The limits of quantification and detection were between 1 and 10 ng/mL using 0.25 mL of sample. The extraction efficiencies varied between 26 and 85%. This analytical method is the first allowing the for determination of cannabinoids in urine samples using MEPS, a fast, simple, and low-cost alternative to conventional techniquesinfo:eu-repo/semantics/publishedVersio
- …