114 research outputs found
An NMR-based nanostructure switch for quantum logic
We propose a nanostructure switch based on nuclear magnetic resonance (NMR)
which offers reliable quantum gate operation, an essential ingredient for
building a quantum computer. The nuclear resonance is controlled by the magic
number transitions of a few-electron quantum dot in an external magnetic field.Comment: 4 pages, 2 separate PostScript figures. Minor changes included. One
reference adde
Entangled Electronic States in Multiple Quantum-Dot Systems
We present an analytically solvable model of colinear, two-dimensional
quantum dots, each containing two electrons. Inter-dot coupling via the
electron-electron interaction gives rise to sets of entangled ground states.
These ground states have crystal-like inter-plane correlations and arise
discontinously with increasing magnetic field. Their ranges and stabilities are
found to depend on dot size ratios, and to increase with .Comment: To appear in Physical Review B (in press). RevTeX file. Figures
available from [email protected]
Renal prostacyclin influences renal function in non-azotemic cirrhotic patients treated with furosemide
The influence of prostaglandins on renal function changes induced by furosemide was analyzed in 21 non-azotemic cirrhotic patients with ascites. Patients were studied in two periods of 120 min immediately before and after furosemide infusion (20 mg, ev). Furosemide caused an increase in creatinine clearance in 15 patients (group A: 99 +/- 7 vs. 129 +/- 5 ml/min; mean +/- S.E.) and a reduction in the remaining six (group B: 102 +/- 13 vs. 71 +/- 9 ml/min). Parallel changes were observed in the urinary excretion of 6-Keto-prostaglandin-F1 alpha (metabolite of renal prostacyclin) which augmented after furosemide in 14 of the 15 patients from group A (478 +/- 107 vs. 1034 +/- 159 pg/min, p less than 0.001) and decreased in all patients from group B (1032 +/- 240 vs. 548 +/- 136 pg/min, p less than 0.05). In contrast, the urinary excretion of prostaglandin E2 was stimulated by furosemide in all patients (group A, 92 +/- 19 vs. 448 +/- 60 pg/min, p less than 0.001; and group B, 209 +/- 63 vs. 361 +/- 25 pg/min, p less than 0.05). In all of the patients furosemide-induced changes (post- minus pre-furosemide values) in creatinine clearance were closely correlated in a direct and linear fashion with those in 6-Keto-prostaglandin-F1 alpha (r = 0.74; p less than 0.001). These changes were associated with a higher furosemide-induced natriuresis in group A than in group B (641 +/- 68 vs. 302 +/-- 46 mumol/min, p less than 0.001
Spin-based quantum information processing with semiconductor quantum dots and cavity QED
A quantum information processing scheme is proposed with semiconductor
quantum dots located in a high-Q single mode QED cavity. The spin degrees of
freedom of one excess conduction electron of the quantum dots are employed as
qubits. Excitonic states, which can be produced ultrafastly with optical
operation, are used as auxiliary states in the realization of quantum gates. We
show how properly tailored ultrafast laser pulses and Pauli-blocking effects,
can be used to achieve a universal encoded quantum computing.Comment: RevTex, 2 figure
Regulatory effects of miR-19a on MAD2 expression and tumorigenesis in gastric cancer
Gastric cancer (GC) is worldwide the sixth most diagnosed and third leading cause of cancer deaths, with poor and late prognosis, probably due to post-surgery adjuvant treatment resistance and lack of a thorough panel of prognostic markers. We have previously shown that mitotic arrest deficient 2 (MAD2, encoded by MAD2L1), a key protein of the spindle assembly checkpoint, is relevant in GC cells; its interference impairs migration and growth, while its overexpression correlates with tumorigenesi
Mixing Bandt-Pompe and Lempel-Ziv approaches: another way to analyze the complexity of continuous-states sequences
In this paper, we propose to mix the approach underlying Bandt-Pompe
permutation entropy with Lempel-Ziv complexity, to design what we call
Lempel-Ziv permutation complexity. The principle consists of two steps: (i)
transformation of a continuous-state series that is intrinsically multivariate
or arises from embedding into a sequence of permutation vectors, where the
components are the positions of the components of the initial vector when
re-arranged; (ii) performing the Lempel-Ziv complexity for this series of
`symbols', as part of a discrete finite-size alphabet. On the one hand, the
permutation entropy of Bandt-Pompe aims at the study of the entropy of such a
sequence; i.e., the entropy of patterns in a sequence (e.g., local increases or
decreases). On the other hand, the Lempel-Ziv complexity of a discrete-state
sequence aims at the study of the temporal organization of the symbols (i.e.,
the rate of compressibility of the sequence). Thus, the Lempel-Ziv permutation
complexity aims to take advantage of both of these methods. The potential from
such a combined approach - of a permutation procedure and a complexity analysis
- is evaluated through the illustration of some simulated data and some real
data. In both cases, we compare the individual approaches and the combined
approach.Comment: 30 pages, 4 figure
Altered liver gene expression in CCl4-cirrhotic rats is partially normalized by insulin-like growth factor-I
We have previously shown that the administration of low doses of insulin-like growth factor-I (IGF-I) to CCl4-cirrhotic rats improves liver function and reduces fibrosis. To better understand the mechanisms behind the hepatoprotective effects of IGF-I, and to identify those genes whose expression is affected in cirrhosis and after IGF-1 treatment, we have performed differential display of mRNA analysis by means of polymerase chain reaction (PCR) in livers from control and CCl4-cirrhotic rats treated or not with IGF-I. We have identified 16 genes that were up- or down-regulated in the cirrhotic liver. IGF-I treatment partially normalized the expression of eight of these genes, including serine proteinase inhibitors such as serpin-2 and alpha-1-antichymotripsin, alpha-1-acid glycoprotein, and alpha-2u-globulin. Additionally, we show that IGF-I enhanced the regenerative activity in the cirrhotic liver, as determined by the increased expression of the proliferating cell nuclear antigen (PCNA). Finally, IGF-I treatment partially restored the expression of growth hormone receptor (GHR) and the levels of global genomic DNA methylation, which are reduced in human and experimental cirrhosis. Taken together, our observations confirm the hepatoprotective effects of IGF-I, and suggest that this action can be exerted in part through the normalization of liver gene expression, growth hormone (GH) responsiveness and global genomic DNA methylation
Renal hemodynamics and the renin-angiotensin system in cirrhosis
The interrelationship between renal hemodynamics and the renin-angiotensin-aldosterone system in 28 nonazotemic cirrhotic patients has been studied. Patients were divided into three groups: A) Patients without ascites nor edema; B) Patients with ascites and a relatively high sodium excretion (41.9 ± 12.9 mmol/day); and C) Patients with ascites and very low sodium excretion (4.8 ± 0.6 mmol/day). Renin and aldosterone levels significantly increased in group C. A significant correlation was observed between plasma aldosterone concentration and urinary sodium excretion, and between plasma renin activity and aldosterone levels. There were no significant differences in urine flow, glomerular filtration rate, effective renal plasma flow, or renal blood flow between the three groups of patients, in spite of marked differences in renin and aldosterone levels. Renal perfusion was not related to plasma renin activity either in the overall sample of patients or in the individual groups. These results show that factors other than total renal perfusion are involved in renin secretion in cirrhosis
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