Generation of Arbitrary Frequency Chirps with a Fiber-Based Phase Modulator and Self-Injection-Locked Diode Laser

We present a novel technique for producing pulses of laser light whose frequency is arbitrarily chirped. The output from a diode laser is sent through a fiber-optical delay line containing a fiber-based electro-optical phase modulator. Upon emerging from the fiber, the phase-modulated pulse is used to injection-lock the laser and the process is repeated. Large phase modulations are realized by multiple passes through the loop while the high optical power is maintained by self-injection-locking after each pass. Arbitrary chirps are produced by driving the modulator with an arbitrary waveform generator

High order amplitude equation for steps on creep curve

We consider a model proposed by one of the authors for a type of plastic instability found in creep experiments which reproduces a number of experimentally observed features. The model consists of three coupled non-linear differential equations describing the evolution of three types of dislocations. The transition to the instability has been shown to be via Hopf bifurcation leading to limit cycle solutions with respect to physically relevant drive parameters. Here we use reductive perturbative method to extract an amplitude equation of up to seventh order to obtain an approximate analytic expression for the order parameter. The analysis also enables us to obtain the bifurcation (phase) diagram of the instability. We find that while supercritical bifurcation dominates the major part of the instability region, subcritical bifurcation gradually takes over at one end of the region. These results are compared with the known experimental results. Approximate analytic expressions for the limit cycles for different types of bifurcations are shown to agree with their corresponding numerical solutions of the equations describing the model. The analysis also shows that high order nonlinearities are important in the problem. This approach further allows us to map the theoretical parameters to the experimentally observed macroscopic quantities.Comment: LaTex file and eps figures; Communicated to Phys. Rev.

BRIEF NOTES Response of a Nonlinear System Under Combined Parametric and Forcing Excitation

In this Note we study a nonlinear second-order system subjected to combined parametric and forcing excitations. The paper may be regarded as an extension of 3 In The results of The system to be studied is governed by M is a small parameter. In addition to equation It consists of two parts. One is the 1/2-order subharmonic oscillation with amplitude coefficients A and B. The second part is a forced oscillation which has the same frequency as the external excitation. For the stationary amplitudes^/! and B we get from We immediately see that A = B = 0 is a solution of (5) regardless whether g = 0 or not, because is = is ~ 0 for A = B = 0, even wheng 9^ 0, as it can be seen from (6). The solution A =B = 0 corresponds, of course, to a response which is devoid of the 1/2-order subharmonic. In solving (5) for A ^ 0, B ^ 0 there are two basic difficulties. One has to do with the sgn xo term and, hence, all the j-factors in (5). As A and B are still unknown at the outset the term cannot be calculated explicitly. Only for g = 0 can The second difficulty is in finding an efficient way of solving Substituting Where the coefficients po,. • . , qa are functions of X. By requiring that these two equations must have a common root, the value of X is determined. The condition which the coefficients of (9) have to fulfill is that a certain determinant which is called the resultant of the two polynomials [7, p. 175] With the value of X determined from (10) by means of a numerical iteration we evaluate the roots of the two polynomials of (9) and pick that root which is common to both. Having obtained B, we calculate A from In this manner the influence of all the parameters on the stationary response amplitude may be studied. As already mentioned A = B = Journal of Applied Mechanics MARCH 1977 / 17

Alignment of the ALICE Inner Tracking System with cosmic-ray tracks

37 pages, 15 figures, revised version, accepted by JINSTALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 micron in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10^5 charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.Peer reviewe

Identification of mitochondrial toxicants by combined in silico and in vitro studies: a structure-based view on the adverse outcome pathway

Toxicolog

Influence of muscle fitness test performance on metabolic risk factors among adolescent girls

<p>Abstract</p> <p>Background</p> <p>The purpose of this study was to examine the association between muscular fitness (MF), assessed by 2 components of Fitnessgram test battery, the Curl-Up and Push-Ups tests and the metabolic risk score among adolescent girls.</p> <p>Methods</p> <p>A total of 229 girls (aged 12-15 years old) comprised the sample of this study. Anthropometric data (height, body mass, waist circumference) were collected. Body mass index (BMI) was also calculated. Muscular strength was assessed taking into account the tests that comprised the FITNESSGRAM test battery, i.e. the curl-up and the push-up. Participants were then categorized in one of 3 categories according the number of tests in which they accomplished the scores that allow them to be classified in health or above health zone. The blood pressure [BP], fasting total cholesterol [TC], low density lipoprotein-cholesterol [LDL-C], high density lipoprotein-cholesterol [HDL-C], triglycerides [TG], glucose, and a metabolic risk score (MRS) were also examined. Physical Activity Index (PAI) was obtained by questionnaire.</p> <p>Results</p> <p>Higher compliance with health-zone criteria (good in the 2 tests), adjusted for age and maturation, were positive and significantly (p ≤ 0.05) associated with height (r = 0.19) and PAI (r = 0.21), while a significant but negative association was found for BMI (r = -0.12); WC (r = -0.19); TC (r = -0.16); TG (r = -0.16); LDL (r = -0.16) and MRS (r = -0.16). Logistic regression showed that who were assigned to MF fittest group were less likely (OR = 0.27; p = 0.003) to be classified overweight/obese and less likely (OR = 0.26; p = 0.03) to be classified as having MRS. This last association was also found for those whom only performed 1 test under the health zone (OR = 0.23; p = 0.02).</p> <p>Conclusions</p> <p>Our data showed that low strength test performance was associated with increased risk for obesity and metabolic risk in adolescent girls even after adjustment for age and maturation.</p

Clinical Characterization and Long-Term Outcome in Children and Adults With Anti-AMPA Receptor Encephalitis.

Anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor (anti-AMPAR) encephalitis manifests as limbic encephalitis in adults and is often associated with cancer. Although some reports suggest that it may occur in children, the clinical features in this population, as well as the prognostic factors and long-term outcomes in children and adults, are unknown. We performed a retrospective, international collaborative study of patients with anti-AMPAR encephalitis. Clinical information was reviewed, together with data from published pediatric patients. Clinical features of children and adults were compared with nonparametric tests. Survival rates (Kaplan-Meier curves) were compared using log-rank tests. Prognostic factors of poor outcome (modified Rankin Scale score &gt;2) were identified using logistic regression models. A total of 115 patients were included, of whom 84 (71 adults, 13 children) had only AMPAR antibodies and 31 (27 adults, 4 children) had additional concurrent neural antibodies. Among patients with AMPAR antibodies alone, tumors were identified in 37 adults (56%) and none of the children (p &lt; 0.0001). Children were more likely than adults to have behavioral/psychiatric symptoms (5/13, 39%, vs 8/71, 11%, p = 0.026) at onset, cerebellar dysfunction (6/13, 46%, vs 7/68, 10% p = 0.005) or movement disorders (5/13, 39%, vs 8/67, 12%, p = 0.032) during the disease course, and extratemporal brain MRI lesions (4/9, 44%, vs 5/44, 11%, p = 0.035). Among 34 patients with prolonged follow-up (&gt;24 months), long-term neurocognitive sequelae were reported in 23 (68%), all adults. Failure to respond to first-line immunotherapy at multivariable analysis predicted a poor outcome (OR 8.0, 95% CI 1.1-59.2, p = 0.043). Among the 31 patients with concurrent neural autoantibodies, 22 (79%) had a tumor; those with high-risk antibodies had lower survival rates (p = 0.008). Children and adults with anti-AMPAR encephalitis show distinct clinical-radiologic features. At long-term follow-up, 68% of patients, all adults, have neurologic sequelae, with failure to respond to first-line immunotherapy being associated with worse outcomes

Predicting drug pharmacokinetics and effect in vascularized tumors using computer simulation

In this paper, we investigate the pharmacokinetics and effect of doxorubicin and cisplatin in vascularized tumors through two-dimensional simulations. We take into account especially vascular and morphological heterogeneity as well as cellular and lesion-level pharmacokinetic determinants like P-glycoprotein (Pgp) efflux and cell density. To do this we construct a multi-compartment PKPD model calibrated from published experimental data and simulate 2-h bolus administrations followed by 18-h drug washout. Our results show that lesion-scale drug and nutrient distribution may significantly impact therapeutic efficacy and should be considered as carefully as genetic determinants modulating, for example, the production of multidrug-resistance protein or topoisomerase II. We visualize and rigorously quantify distributions of nutrient, drug, and resulting cell inhibition. A main result is the existence of significant heterogeneity in all three, yielding poor inhibition in a large fraction of the lesion, and commensurately increased serum drug concentration necessary for an average 50% inhibition throughout the lesion (the IC50 concentration). For doxorubicin the effect of hypoxia and hypoglycemia (“nutrient effect”) is isolated and shown to further increase cell inhibition heterogeneity and double the IC50, both undesirable. We also show how the therapeutic effectiveness of doxorubicin penetration therapy depends upon other determinants affecting drug distribution, such as cellular efflux and density, offering some insight into the conditions under which otherwise promising therapies may fail and, more importantly, when they will succeed. Cisplatin is used as a contrast to doxorubicin since both published experimental data and our simulations indicate its lesion distribution is more uniform than that of doxorubicin. Because of this some of the complexity in predicting its therapeutic efficacy is mitigated. Using this advantage, we show results suggesting that in vitro monolayer assays using this drug may more accurately predict in vivo performance than for drugs like doxorubicin. The nonlinear interaction among various determinants representing cell and lesion phenotype as well as therapeutic strategies is a unifying theme of our results. Throughout it can be appreciated that macroscopic environmental conditions, notably drug and nutrient distributions, give rise to considerable variation in lesion response, hence clinical resistance. Moreover, the synergy or antagonism of combined therapeutic strategies depends heavily upon this environment