Cosmological inflation driven by holonomy corrections of loop quantum cosmology

At the level of heuristic effective dynamics, we investigate the cosmological inflation with holonomy corrections of loop quantum cosmology (LQC) in the $k=0$ Friedmann-Robertson-Walker model with a single inflaton field subject to a simple potential. In the symmetric bouncing scenario of LQC, the condition for occurrence of the quantum bounce naturally and uniquely fixes the initial conditions at the bouncing epoch. Around the quantum bounce, the universe undergoes a short super-inflationary phase, which drives the inflaton field to its potential hill and thus sets the proper initial conditions for the standard slow-roll inflation. Between the super-inflation and the standard inflation, there is a non-inflationary phase, which violates the slow-roll condition. The violation of slow roll is expected to give some suppression on the low angular power spectrum of the cosmic microwave background and different orders of holonomy corrections shall yield different suppressions.Comment: 7 pages, 2 figures, 1 table; one reference added

Clinical Experience and Sexual Function Outcome of Patients With Priapism Treated With Penile Cavernosal-Dorsal Vein Shunt Using Saphenous Vein Graft

OBJECTIVES To assess the outcome of new penile cavernosal-dorsal vein shunt using a saphenous vein graft. Traditional surgeries for priapism have high failure rate and subsequent impotence. METHODS We reviewed the medical records of, and administered a questionnaire and the International Index of Erectile Function to, 16 consecutive patients with priapism who had treated with the penile cavernosal-dorsal vein shunt from 1997 to 2007. Their age was 15-65 years. The duration of ischemic priapism was 32 hours to 8 days. Ten patients had previously undergone shunt surgery by other urologists. Of the 16 patients, 5 returned the questionnaires. RESULTS Priapism resolved or was improved after surgery in all 16 patients. One patient was lost to follow-up. One pediatric patient was excluded from the analysis. One patient with nonischemic priapism continued to have sexual intercourse. Of the 13 adult patients with ischemic priapism and follow-up for ≤ 6.5 years, 3 patients had no erection, 1 had very little erection, and 9 (69%) had erection. Of the 9 patients with erections possible, six had had sexual intercourse (International Index of Erectile Function score 32-70) and 3 had not; 1 had a mental disorder, 1 was in prison, and for 1, the reason was unknown. After surgery, color Doppler ultrasound studies showed a patent shunt in all patients and restoration of cavernosal arterial flow in 12 of 13 patients studied. CONCLUSIONS A penile cavernosal-dorsal shunt appears effective for priapism. It resulted in priapism resolution even in patients who had experienced a previous failed cavernosal-glandular shunt or cavernosalspongiosal shunt, with a high rate of sexual function preservation

A study of forced flow separation in rocket nozzle

The characteristics of flow profile in a rocket nozzle during the start transient were investigated as well as possibilities of reducing the side-load thrust by sticking trip wires in the nozzle. To simplify the geometry of flow configuration around the trip wire, it was assumed that the flow is passing through square steps instead of round wires. Since a purely analytic solution is not available, a series of semiempirical solutions was proposed

Homologous Muscle Contraction during Unilateral Movement Does Not Show a Dominant Effect on Leg Representation of the Ipsilateral Primary Motor Cortex

Co-activation of homo- and heterotopic representations in the primary motor cortex (M1) ipsilateral to a unilateral motor task has been observed in neuroimaging studies. Further analysis showed that the ipsilateral M1 is involved in motor execution along with the contralateral M1 in humans. Additionally, transcranial magnetic stimulation (TMS) studies have revealed that the size of the co-activation in the ipsilateral M1 has a muscle-dominant effect in the upper limbs, with a prominent decline of inhibition within the ipsilateral M1 occurring when a homologous muscle contracts. However, the homologous muscle-dominant effect in the ipsilateral M1 is less clear in the lower limbs. The present study investigates the response of corticospinal output and intracortical inhibition in the leg representation of the ipsilateral M1 during a unilateral motor task, with homo- or heterogeneous muscles. We assessed functional changes within the ipsilateral M1 and in corticospinal outputs associated with different contracting muscles in 15 right-handed healthy subjects. Motor tasks were performed with the right-side limb, including movements of the upper and lower limbs. TMS paradigms were measured, consisting of short-interval intracortical inhibition (SICI) and recruitment curves (RCs) of motor evoked potentials (MEPs) in the right M1, and responses were recorded from the left rectus femoris (RF) and left tibialis anterior (TA) muscles. TMS results showed that significant declines in SICI and prominent increases in MEPs of the left TA and left RF during unilateral movements. Cortical activations were associated with the muscles contracting during the movements. The present data demonstrate that activation of the ipsilateral M1 on leg representation could be increased during unilateral movement. However, no homologous muscle-dominant effect was evident in the leg muscles. The results may reflect that functional coupling of bilateral leg muscles is a reciprocal movement

Model-based signal processing techniques for ultrasonic flaw detection: simulation studies

The ultrasonic signals observed in inspection processes can often be accurately predicted by suitable measurement models. These model predictions can be used to provide important information to guide the development of subsequent signal processing algorithms. Here such a hybrid use of ultrasonic modeling and signal processing is demonstrated in the context of the problem of detecting ultrasonic flaw signals in noise. In particular, we wish to apply this hybrid methodology as an initial approach to solving the problem of detecting hard-alpha inclusions in titanium alloys

Paying attention to social media stocks

Social media has reshaped business models, economies, politics, and culture around the world. In this paper, we identified social media stocks from various sectors by using a strict, academic definition and then studied their performance and return characteristics. Multivariate regression results demonstrate that being recognized as a social media firm yields extra return. The performance of social media stocks is not associated with macro-level sentiment, but rather with firm-level attention paid by potential investors. Causality tests indicate that the default risk premium and volatility have incremental power in explaining the performance of social media stocks

Quantum Mechanical Search and Harmonic Perturbation

Perturbation theory in quantum mechanics studies how quantum systems interact with their environmental perturbations. Harmonic perturbation is a rare special case of time-dependent perturbations in which exact analysis exists. Some important technology advances, such as masers, lasers, nuclear magnetic resonance, etc., originated from it. Here we add quantum computation to this list with a theoretical demonstration. Based on harmonic perturbation, a quantum mechanical algorithm is devised to search the ground state of a given Hamiltonian. The intrinsic complexity of the algorithm is continuous and parametric in both time T and energy E. More precisely, the probability of locating a search target of a Hamiltonian in N-dimensional vector space is shown to be 1/(1+ c N E^{-2} T^{-2}) for some constant c. This result is optimal. As harmonic perturbation provides a different computation mechanism, the algorithm may suggest new directions in realizing quantum computers.Comment: 6 pages, 4 figures, revtex