Magneto-optical response of layers of semiconductor quantum dots and nanorings

In this paper a comparative theoretical study was made of the magneto-optical response of square lattices of nanoobjects (dots and rings). Expressions for both the polarizability of the individual objects as their mutual electromagnetic interactions (for a lattice in vacuum) was derived. The quantum-mechanical part of the derivation is based upon the commonly used envelope function approximation. The description is suited to investigate the optical response of these layers in a narrow region near the interband transitions onset, particularly when the contribution of individual level pairs can be separately observed. A remarkable distinction between clearly quantum-mechanical and classical electromagnetic behavior was found in the shape and volume dependence of the polarizability of the dots and rings. This optical response of a single plane of quantum dots and nanorings was explored as a function of frequency, magnetic field, and angle of incidence. Although the reflectance of these layer systems is not very strong, the ellipsometric angles are large. For these isolated dot-ring systems they are of the order of magnitude of degrees. For the ring systems a full oscillation of the optical Bohm-Ahronov effect could be isolated. Layers of dots do not display any remarkable magnetic field dependence. Both type of systems, dots and rings, exhibit an outspoken angular-dependent dichroism of quantum-mechanical origin

Integrating a web-based system with business processes in closed loop supply chains

Closed Loop Supply Chains include operations for physical collection of end-of-use products, selection based on their configuration and/or condition and decision making for reuse, remanufacturing or recycling. Uncertainty factors regarding the time, place of origin, and status of returns introduce many difficulties in planning these operations. With the aim to minimize such problems, this paper presents an architecture for virtual reverse logistics networks and an implementation for end-of-use PCs. The virtual reverse logistics network for PCs relies on E-commerce and WWW technologies for remote monitoring and benchmarking, instead of physical transportation and inspection. A configuration monitoring and benchmarking agent screens the computer that is about to enter the end-of-use stream and registers the data in the system’s databases. The virtual reverse logistics network regards all incoming PCs as submitted offers. Also, users or agents may explicitly register requests for PCs or modules. Offers are matched to requests with a decision support system to provide recommendations for reuse, remanufacturing or recycling of end-of-use PCs. An electronic marketplace matches requests and offers. The proposed architecture diminishes the uncertainty factors and provides us with an understanding on what is missing and it is likely to have a positive impact to the development of virtual reverse logistics networks for computers and other equipment with embedded logic.business processes;Closed Loop Supply Chains;virtual reverse logistics networks;web-based system

STRENGTH TRAINING FOR POLYMYOSlTIS PATIENT

INTRODUCTlON-This paper is presented for the demonstration of people suffering from polymyositis upon rehabilitation can regain muscular strength and quality of life. This disease usually attacks people reaching the age of 50 years and above with malignancy or as an idiopathic process in its own rights. This is a diffuse inflammatory disease involving asymmetrical wasting of muscular tissue leading to loss of power. In Malaysia, a top soccer player died few years ago because of a disease of this nature. This group of disorder is heterogeneous and rare, its incidence is probably 3 per million population per year in the United Kingdom. METHODS- This experiment looks into the aspect of a strength training program to prevent disuse atrophy and contracture of muscle caused by the nature of this disease. Because of its rarity, only ONE female subject of 57 years of age diagnosed by her physician to be suffering from polymyositis has agreed to go through this strength training program based on the concept of conscious state of contraction. Subject before the strength training program was under prescription of 2 prednisone (steroids) tablets per day. Subject is unable to sit up or perform any personal mobilisation on her own without assistance. This program involves mobilisation of the joints and the subject must be taught to be conscious about the movement as in Imagined Training'(Enoka, 1994). The subject must know that at will the command from the brain centre, will innervate the muscle fibres which leads to the contraction of that specific muscle or joint that will initiate motion. CONCLUSION-The difficulties in this experiment is the ability to concentrate on the contraction of each muscle group because every contraction and relaxation of a muscle are actions series done quite subconsciously. The expression of voluntary strength & power may be likened to a skilled art of which the changes in nervous system that enhance strength is referred as neural adaptation (Sale, 1986). Because of the muscular atrophy, it is rather impossible for the subject to perform compound movement like squatting, presses, etc.. Exercises on the initial phase were joints mobilisation and on the 2nd. month, close kinetic movement like knee extensions were selected. During the 3rd. month, performance of personal movement were profound. This concept of training is highly targeted to the neural system which can help the subject in the mind and muscle connection and the ability to innervate the muscle fibres accordingly. This innervation in return develops a stronger and hypertrophied muscle. REFERENCES- Enoka, R. (1 994). Neurornechanical basis of kinesiology, 2nd. ed. Sale, D.G. (1986). Neural Adaptation in strength and power training. Human Muscle Power, pg. 289

Effective scraping in a scraped surface heat exchanger: some fluid flow analysis

An outline of mathematical models that have been used to understand the behaviour of scraped surface heat exchangers is presented. In particular the problem of the wear of the blades is considered. A simple model, exploiting known behaviour of viscous flow in corners and in wedges, and accounting for the forces on the blade is derived and solutions generated. The results shows initial rapid wear but that the wear rate goes to zero

Supersymmetric codimension-two branes and U(1)_R mediation in 6D gauged supergravity

We construct a consistent supersymmetric action for brane chiral and vector multiplets in a six-dimensional chiral gauged supergravity. A nonzero brane tension can be accommodated by allowing for a brane-localized Fayet-Iliopoulos term proportional to the brane tension. When the brane chiral multiplet is charged under the bulk U(1)_R, we obtain a nontrivial coupling to the extra component of the U(1)_R gauge field strength as well as a singular scalar self-interaction term. Dimensionally reducing to 4D on a football supersymmetric solution, we discuss the implication of such interactions for obtaining the U(1)_R D-term in the 4D effective supergravity. By assuming the bulk gaugino condensates and nonzero brane F- and/or D-term for the uplifting potential, we have all the moduli stabilized with a vanishing cosmological constant. The brane scalar with nonzero R charge then gets a soft mass of order the gravitino mass. The overall sign of the soft mass squared depends on the sign of the R charge as well as whether the brane F- or D-term dominates.Comment: 28 pages, no figures, version to appear in JHE

Volume stabilization in a warped flux compactification model

We investigate the stability of the extra dimensions in a warped, codimension two braneworld that is based upon an Einstein-Maxwell-dilaton theory with a non-vanishing scalar field potential. The braneworld solution has two 3-branes, which are located at the positions of the conical singularities. For this type of brane solution the relative positions of the branes (the shape modulus) is determined via the tension-deficit relations, if the brane tensions are fixed. However, the volume of the extra dimensions (the volume modulus) is not fixed in the context of the classical theory, implying we should take quantum corrections into account. Hence, we discuss the one-loop effective potential of the volume modulus for a massless, minimally coupled scalar field.Comment: 25 pages, 8 figures, typos correcte

Is there a role for prophylactic mesh in abdominal wall closure after emergency laparotomy? A systematic review and meta-analysis

Background Incisional hernias are a common complication of emergency laparotomy and are associated with significant morbidity. Recent studies have found a reduction in incisional hernias when mesh is placed prophylactically during abdominal closure in elective laparotomies. This systematic review will assess the safety and efficacy of prophylactic mesh placement in emergency laparotomy. Methods A systematic review was performed according to the PROSPERO registered protocol (CRD42018109283). Papers were dual screened for eligibility, and included when a comparison was made between closure with prophylactic mesh and closure with a standard technique, reported using a comparative design (i.e. case–control, cohort or randomised trial), where the primary outcome was incisional hernia. Bias was assessed using the Cochrane risk of bias in non-randomised studies tool. A meta-analysis of incisional hernia rate was performed to estimate risk ratio using a random effects model (Mantel–Haenszel approach). Results 332 studies were screened for eligibility, 29 full texts were reviewed and 2 non-randomised studies were included. Both studies were biased due to confounding factors, as closure technique was based on patient risk factors for incisional hernia. Both studies found significantly fewer incisional hernias in the mesh groups [3.2% vs 28.6% (p < 0.001) and 5.9% vs 33.3% (p = 0.0001)]. A meta-analysis of incisional hernia risk favoured prophylactic mesh closure [risk ratio 0.15 (95% CI 0.6–0.35, p < 0.001)]. Neither study found an association between mesh and infection or enterocutaneous fistula. Conclusion This review found that there are limited data to assess the effect or safety profile of prophylactic mesh in the emergency laparotomy setting. The current data cannot reliably assess the use of mesh due to confounding factors, and a randomised controlled trial is required to address this important clinical question

General Axisymmetric Solutions and Self-Tuning in 6D Chiral Gauged Supergravity

We re-examine the properties of the axially-symmetric solutions to chiral gauged 6D supergravity, recently found in refs. hep-th/0307238 and hep-th/0308064. Ref. hep-th/0307238 finds the most general solutions having two singularities which are maximally-symmetric in the large 4 dimensions and which are axially-symmetric in the internal dimensions. We show that not all of these solutions have purely conical singularities at the brane positions, and that not all singularities can be interpreted as being the bulk geometry sourced by neutral 3-branes. The subset of solutions for which the metric singularities are conical precisely agree with the solutions of ref. hep-th/0308064. Establishing this connection between the solutions of these two references resolves a minor conflict concerning whether or not the tensions of the resulting branes must be negative. The tensions can be both negative and positive depending on the choice of parameters. We discuss the physical interpretation of the non-conical solutions, including their significance for the proposal for using 6-dimensional self-tuning to understand the small size of the observed vacuum energy. In passing we briefly comment on a recent paper by Garriga and Porrati which criticizes the realization of self-tuning in 6D supergravity.Comment: 27 pages, 1 figure; JHEP3 style; Some references added, and discussion of tension constraints and unwarped solutions made more explici

3-Form Flux Compactification of Salam-Sezgin Supergravity

The compactification of 6 dimensional Salam-Sezgin model in the presence of 3-form flux H is investigated. We find a torus topology for this compactification with two cusps which are the places of branes, while at the limit of large size L of the compact direction we also obtain sphere topology. This resembles the Randall-Sundrum I,II model. The branes at one of the cusps can be chosen to be 3- and 4-branes which fill our 4-dimensional space together with the fact that H=0 at this position restores the Lorentz symmetry. This compactification also provides an example for the so-called `time warp' solution, [0812.5107 [hep-th]]. According to a no-go theorem in $d\ne 6$, the time warp compactification violates the null energy condition. While the theorem is quiet for d=6, our model gives a time warp compactification which satisfies the null energy condition. We also derive the four dimensional effective Planck mass which is not obvious due to the time warp nature of the solution.Comment: 19 pages, 5 fig

Supersymmetric codimension-two branes in six-dimensional gauged supergravity

We consider the six-dimensional Salam-Sezgin supergravity in the presence of codimension-2 branes. In the case that the branes carry only tension, we provide a way to supersymmetrise them by adding appropriate localised Fayet-Iliopoulos terms and localised corrections to the Chern-Simons term and modifying accordingly the fermionic supersymmetry transformations. The resulting brane action has N=1 supersymmetry (SUSY). We find the axisymmetric vacua of the system and show that one has unwarped background solutions with "football"-shaped extra dimensions which always respect N=1 SUSY for any value of the equal brane tensions, in contrast with the non-supersymmetric brane action background. Finally, we generically find multiple zero modes of the gravitino in this background and discuss how one could obtain a single chiral zero mode present in the low energy spectrum.Comment: 21 pages, no figures, A sign error in the gauge potential at the lower brane corrected and its consequent effect discusse