Fast-forward approach to stochastic heat engine.

The fast-forward (FF) scheme proposed by Masuda and Nakamura [Proc. R. Soc. A 466, 1135 (2010)1364-502110.1098/rspa.2009.0446] in the context of conservative quantum dynamics can reproduce a quasistatic dynamics in an arbitrarily short time. We apply the FF scheme to the classical stochastic Carnot-like heat engine which is driven by a Brownian particle coupled with a time-dependent harmonic potential and working between the high- (T_{h}) and low- (T_{c}) temperature heat reservoirs. Concentrating on the underdamped case where momentum degree of freedom is included, we find the explicit expressions for the FF protocols necessary to accelerate both the isothermal and thermally adiabatic processes and obtain the reversible and irreversible works. The irreversible work is shown to consist of two terms with one proportional to and the other inversely proportional to the friction coefficient. The optimal value of efficiency η at the maximum power of this engine is found to be η^{*}=1/2{1+1/2(T_{c}/T_{h})^{1/2}-5/4T_{c}/T_{h}+O[(T_{c}/T_{h})^{3/2}]} and η^{*}=1-(T_{c}/T_{h})^{1/2}, respectively, in the cases of strong and weak dissipation. The result is justified for a wide family of time-scaling functions, making the FF protocols very flexible. We also revealed that the accelerated full cycle of the Carnot-like stochastic heat engine cannot be conceivable within the framework of the overdamped case, and the power and efficiency can be evaluated only when the momentum degree of freedom is taken into consideration.

Quantum gas in the fast forward scheme of adiabatically expanding cavities: Force and equation of state.

With use of the scheme of fast forward which realizes quasistatic or adiabatic dynamics in shortened timescale, we investigate a thermally isolated ideal quantum gas confined in a rapidly dilating one-dimensional (1D) cavity with the time-dependent size L=L(t). In the fast-forward variants of equation of states, i.e., Bernoulli's formula and Poisson's adiabatic equation, the force or 1D analog of pressure can be expressed as a function of the velocity (L[over ̇]) and acceleration (L[over ̈]) of L besides rapidly changing state variables like effective temperature (T) and L itself. The force is now a sum of nonadiabatic (NAD) and adiabatic contributions with the former caused by particles moving synchronously with kinetics of L and the latter by ideal bulk particles insensitive to such a kinetics. The ratio of NAD and adiabatic contributions does not depend on the particle number (N) in the case of the soft-wall confinement, whereas such a ratio is controllable in the case of hard-wall confinement. We also reveal the condition when the NAD contribution overwhelms the adiabatic one and thoroughly changes the standard form of the equilibrium equation of states.

H3K36 Trimethylation-Mediated Epigenetic Regulation is Activated by Bam and Promotes Germ Cell Differentiation During Early Oogenesis in Drosophila.

Epigenetic silencing is critical for maintaining germline stem cells in Drosophila ovaries. However, it remains unclear how the differentiation factor, Bag-of-marbles (Bam), counteracts transcriptional silencing. We found that the trimethylation of lysine 36 on histone H3 (H3K36me3), a modification that is associated with gene activation, is enhanced in Bam-expressing cells. H3K36me3 levels were reduced in flies deficient in Bam. Inactivation of the Set2 methyltransferase, which confers the H3K36me3 modification, in germline cells markedly reduced H3K36me3 and impaired differentiation. Genetic analyses revealed that Set2 acts downstream of Bam. Furthermore, orb expression, which is required for germ cell differentiation, was activated by Set2, probably through direct H3K36me3 modification of the orb locus. Our data indicate that H3K36me3-mediated epigenetic regulation is activated by bam, and that this modification facilitates germ cell differentiation, probably through transcriptional activation. This work provides a novel link between Bam and epigenetic transcriptional control.

High-fidelity rapid ground-state loading of an ultracold gas into an optical lattice.

A protocol is proposed for the rapid coherent loading of a Bose-Einstein condensate into the ground state of an optical lattice, without residual excitation associated with the breakdown of adiabaticity. The driving potential required to assist the rapid loading is derived using the fast-forward technique, and generates the ground state in any desired short time. We propose an experimentally feasible loading scheme using a bichromatic lattice potential, which approximates the fast-forward driving potential with high fidelity.

Bernoulli's formula and Poisson's equations for a confined quantum gas: effects due to a moving piston.

We study a nonequilibrium equation of states of an ideal quantum gas confined in the cavity under a moving piston with a small but finite velocity in the case in which the cavity wall suddenly begins to move at the time origin. Confining ourselves to the thermally isolated process, the quantum nonadiabatic (QNA) contribution to Poisson's adiabatic equations and to Bernoulli's formula which bridges the pressure and internal energy is elucidated. We carry out a statistical mean of the nonadiabatic (time-reversal-symmetric) force operator found in our preceding paper [Nakamura et al., Phys. Rev. E 83, 041133 (2011)] in both the low-temperature quantum-mechanical and high-temperature quasiclassical regimes. The QNA contribution, which is proportional to the square of the piston's velocity and to the inverse of the longitudinal size of the cavity, has a coefficient that is dependent on the temperature, gas density, and dimensionality of the cavity. The investigation is done for a unidirectionally expanding three-dimensional (3D) rectangular parallelepiped cavity as well as its 1D version. Its relevance in a realistic nanoscale heat engine is discussed.

Innexin2 gap junctions in somatic support cells are required for cyst formation and for egg chamber formation in Drosophila.

Germ cells require intimate associations with surrounding somatic cells during gametogenesis. During oogenesis, gap junctions mediate communication between germ cells and somatic support cells. However, the molecular mechanisms by which gap junctions regulate the developmental processes during oogenesis are poorly understood. We have identified a female sterile allele of innexin2 (inx2), which encodes a gap junction protein in Drosophila. In females bearing this inx2 allele, cyst formation and egg chamber formation are impaired. In wild-type germaria, Inx2 is strongly expressed in escort cells and follicle cells, both of which make close contact with germline cells. We show that inx2 function in germarial somatic cells is required for the survival of early germ cells and promotes cyst formation, probably downstream of EGFR pathway, and that inx2 function in follicle cells promotes egg chamber formation through the regulation of DE-cadherin and Bazooka (Baz) at the boundary between germ cells and follicle cells. Furthermore, genetic experiments demonstrate that inx2 interacts with the zero population growth (zpg) gene, which encodes a germline-specific gap junction protein. These results indicate a multifunctional role for Inx2 gap junctions in somatic support cells in the regulation of early germ cell survival, cyst formation and egg chamber formation. Inx2 gap junctions may mediate the transfer of nutrients and signal molecules between germ cells and somatic support cells, as well as play a role in the regulation of cell adhesion.

Topology of magnetic field lines: chaos and bifurcations emerging from two-action systems.

Nonlinear dynamics of magnetic field lines generated by simple electric current elements are investigated. In general, the magnetic field lines show behavior similar to that of the Hamiltonian systems; in fact, they can be generally transformed into Hamiltonian systems with 1.5 degrees of freedom, obey the Kolmogorov-Arnold-Moser (KAM) theorem, and generate chaotic trajectories. In the case where unperturbed systems are described by two action (slow) and one angle (fast) variables, however, it is found that the periodic orbits of the unperturbed systems vanish for arbitrarily small symmetry-breaking perturbations (a breakdown of the KAM theorem) and drifting or periodic trajectories appear. The mechanism of this phenomenon is investigated analytically by weak nonlinear stability analysis. It is also shown numerically that scattering processes of the perturbed system exhibit typical features of chaotic dynamical systems.

Effects of pantothenic acid on testicular function in male rats.

Pantothenic acid (PaA) is a water-soluble vitamin required to sustain various physiological functions in animals. The physiological roles of PaA on testicular function, in particular, testicular endocrinology and sperm mortility, were investigated in rats. Male rats at 3 weeks of age were fed a PaA-free diet or a 0.0016% PaA diet (control) for 7 weeks. Total body weight, as well as the weights of the liver, kidney, pituitary, testis, epididymis, seminal vesicle and prostate; sperm motility; and the plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone and corticosterone were measured in rats at 10 weeks of age. Body weight gain decreased from 5 weeks of age in rats fed the PaA-free diet compared with the control. The relative weights of the testes were significantly higher in the PaA-deficient group compared with the control group. Several parameters of sperm motility were significantly reduced in the PaA-deficient group compared with the control group. In addition, the plasma concentrations of testosterone and corticosterone were significantly lower in the PaA-deficient group compared with the control group, whereas the plasma concentrations of FSH and LH showed no change. These results clearly demonstrate that PaA is an essential factor in testicular endocrinology and sperm motility in male rats.

Effects of pantothenic acid supplementation on adrenal steroid secretion from male rats.

The effects of pantothenic acid-supplementation on the adrenal secretion of corticosterone and progesterone in male rats were investigated using an in vitro cell culture system. Male rats at 21 d of age were given 0.03% pantothenic acid in their drinking water for 9 weeks. After 9 weeks of treatment, the animals were decapitated, and adrenal cells were cultured in the absence or presence of rat adrenocorticotropic hormone (ACTH; 10(-15) to 10(-10) M) and/or ovine prolactin (oPRL; 10(-9) to 10(-7) M) for 4 h. Adrenal cells in pantothenic acid-treated rats exhibited higher basal levels of corticosterone and progesterone than control rats. The response of ACTH and/or PRL on corticosterone and progesterone release was higher in the pantothenic acid-treated rats than in the control rats. In addition, PRL increased the stimulatory effect of ACTH-induced corticosterone secretion in both normal and pantothenic acid-treated rats. These results clearly demonstrated that pantothenic acid supplementation stimulates the ability of adrenal cells in male rats to secrete corticosterone and progesterone. Additionally, these results also showed that pantothenic acid supplementation induced adrenal hyperresponsiveness to ACTH stimulation, and PRL further stimulated adrenal sensitivity to ACTH.

Kramers theory in the relaxation dynamics of a tilted asymmetric periodic potential.

We investigate the low-temperature relaxation dynamics toward a nonequilibrium steady state in a tilted asymmetric periodic potential based on the WKB analysis and the numerical diagonalization of the Fokker-Planck operator. Due to the tilting, the Fokker-Planck operator, and thus the Schrödinger operator associated with it, are non-Hermitian. Therefore, we evaluate the decay rate based on the WKB analysis both for real- and complex-valued eigenvalues. In the tilting range where the double-humped barrier exists, the decay rate is shown to obey a law which is a subtle nonequilibrium extension of the so-called Kramers escape rate. The decay rate for the single-humped barrier case is analyzed as well. The large tilting regime where the barriers no longer exist is also investigated.

Effects of an oscillating field on pattern formation in a ferromagnetic thin film: analysis of patterns traveling at a low velocity.

Magnetic domain patterns under an oscillating field are studied theoretically by using a simple Ising-like model. We propose two ways to investigate the effects of the oscillating field. The first one leads to a model in which rapidly oscillating terms are averaged out and the model can explain the existence of the maximum amplitude of the field for the appearance of patterns. The second one leads to a model that includes the delay of the response to the field and the model suggests the existence of a traveling pattern which moves very slowly compared with the time scale of the driving field.

Role of an intermediate state in homogeneous nucleation.

We explore the role of an intermediate state (phase) in homogeneous nucleation by examining the decay process through a double-humped potential barrier. We analyze the one-dimensional Fokker-Planck (FP) equations with the fourth- and sixth-order Landau potentials. In the low-temperature case, we apply the WKB method to the FP equation and obtain an analytic expression for the decay rate which is accurate for a wide range of depth and curvature of the middle well. In the case of a deep middle well, it reduces to an extended Kramers formula, in which the barrier height in the original formula is replaced by the arithmetic mean height of the higher (outer) and lower (inner) barriers, and the curvature of the initial well in the original one is replaced by the geometric mean curvature of the initial and intermediate wells. In the case of a shallow middle well, the Kramers escape rate is evaluated also within the standard framework of the mean-first-passage-time problem, whose result is consistent with our WKB analysis. Criteria for enhancement of the decay rate are revealed.

Chaos and its quantization in dynamical Jahn-Teller systems.

We investigate the E(g) x in circle e(g) Jahn-Teller system for the purpose of revealing the nature of quantum chaos in crystals. This system simulates the interaction between the nuclear vibrational modes and the electronic motion in non-Kramers doublets for multiplets of transition-metal ions. Inclusion of the anharmonic potential due to the trigonal symmetry in crystals makes the system nonintegrable and chaotic. Besides the quantal analysis of the transition from Poisson to Wigner level statistics with increasing the strength of anharmonicity, we study the effect of chaos on the electronic orbital angular momentum and explore the magnetic g-factor as a function of the system's energy. The regular oscillation of this factor changes to a rapidly decaying irregular oscillation by increasing the anharmonicity (chaoticity).