Chiral rings and GSO projection in Orbifolds

The GSO projection in the twisted sector of orbifold background is sometimes subtle and incompatible descriptions are found in literatures. Here, from the equivalence of partition functions in NSR and GS formalisms, we give a simple rule of GSO projection for the chiral rings of string theory in \C^r/\Z_n, $r=1,2,3$. Necessary constructions of chiral rings are given by explicit mode analysis.Comment: 24 page

Probing resonance decays to two visible and multiple invisible particles

We consider the decay of a generic resonance to two visible particles and any number of invisible particles. We show that the shape of the invariant mass distribution of the two visible particles is sensitive to both the mass spectrum of the new particles, as well as the decay topology. We provide the analytical formulas describing the invariant mass shapes for the nine simplest topologies (with up to two invisible particles in the final state). Any such distribution can be simply categorized by its endpoint, peak location and curvature, which are typically sufficient to discriminate among the competing topologies. In each case, we list the effective mass parameters which can be measured by experiment. In certain cases, the invariant mass shape is sufficient to completely determine the new particle mass spectrum, including the overall mass scale.Comment: Added new figures, conclusions unchanged, published versio

Asymmetric scattering and non-orthogonal mode patterns in optical micro-spirals

Quasi-bound states in an open system do in general not form an orthogonal and complete basis. It is, however, expected that the non-orthogonality is weak in the case of well-confined states except close to a so-called exceptional point in parameter space. We present numerical evidence showing that for passive optical microspiral cavities the parameter regime where the non-orthogonality is significant is rather broad. Here we observe almost-degenerate pairs of well-confined modes which are highly non-orthogonal. Using a non-Hermitian model Hamiltonian we demonstrate that this interesting phenomenon is related to the asymmetric scattering between clockwise and counterclockwise propagating waves in the spiral geometry. Numerical simulations of ray dynamics reveal a clear ray-wave correspondence.Comment: 8 pages, 10 figure

Ethical Price for Essential Pharmaceuticals?

Azidothymidine or AZT is an antiretroviral medication used to prevent and treat HIV/AIDS. Nowadays, AZT remains to be the primary active drug that can elongate the life of infected patients. Without treatment, patients can live for 5 to 10 years after infected. With the treatment, their life expectancy approaches the norm. However, it is important to note that AZT is a life-saver for HIV patients only if they can afford it. An HIV patient needs to spend about $17,000 for AZT every year until the end of his life. Therefore, the estimated lifetime cost of HIV will be$600,000. This premium cost creates an invisible barrier for many patients to access AZT, particularly those without adequate insurance coverage. AZT is not the only medication that has a prohibitively high price. In fact, the price of the drug in the U.S is significantly higher than any other country in the world. For example, the price of Roche’s product Valium is $9.1in the U.S but$3.6 elsewhere. Therefore, many critics claim that the price of many essential pharmaceuticals, such as AZT, is unreasonably and unethical high. Defending for their position, many pharmaceutical companies argue that charging a premium price is necessary to motivate scientific innovation. When a new drug is discovered, a pharmaceutical company can cover that drug under patent protection, meaning that only the company that holds the patent is allowed to manufacture and market the drug. For example, with AZT patent, Burroughs Wellcome becomes the only legal supplier for AZT and, therefore, possesses the entire power to determine the price of this medication. The price of patent drug includes several components: production cost, research and development (R&D) cost, other additional costs (such as marketing), and net profit. After the patent expires, due to the competition of generic drug, the sale could drop by more than 90% and the firm will not be able to incorporate R&D cost into drug’s price anymore. Many companies explain that R&D is extremely expensive, and to keep their companies functioning, they need to recoup the R&D cost before their patents expire. Therefore, they have no choice but charging a premium price on their pharmaceuticals. The premium price of essential pharmaceuticals prevents some patients to have their fulfilled life and, sometimes, indirectly force them to give up their lives. These painful facts raise four main questions that will be addressed in this essay: Who deserves essential drugs? Is it necessary for pharmaceutical firms to charge premium prices for essential drugs to keep companies functioning? Is it just for pharmaceutical firms to charge premium prices for essential drugs? Should someone try to reduce the premium price of essential drugs? If yes, who should do it? I believe that it is not only unnecessary but also unjust to charge a premium price on essential pharmaceuticals. I also believe that government should have the responsibility to ensure that patients can have access to essential medications as they need

An Ethical Market for Kidney?

The kidney performs several vital functions that maintain our general health condition, including filtering waste chemicals out of our blood. Kidney failure is a condition where patients’ kidneys lose their ability to filter the waste from their blood, leading to accumulating toxin in their body. Without any medical care, a patient with kidney failure has a couple days to a couple of weeks to live. One way to elongate the life of the kidney-failure patient is through kidney transplant, where another kidney is implanted into the patient’s body. In the U.S, it is illegal to trade a kidney for money. Therefore, the supply of kidney come from volunteers, which could be living or deceased donors. According to the U.S National Kidney Foundation, the kidney supply can only meet 10% of the demand. From an economic point of view, this current kidney supply system in the U.S is not efficient, since it could not meet the large demand from patients. In 2014, 4,761 patients died while waiting for a kidney transplant. In the same year, there were 3,668 people who became too sick to receive a kidney transplant. On average, there are over 3,000 new patients on the waiting list each month (National Kidney Foundation, 2018). These statistics are the pressure for the scholarly community to figure out a solution for kidney failure patients. Market has a big reputation for its famous function: allocating scarce resources. Facing with the shortage of kidney, a market mechanism is proposed to allocate the kidney, a scarce resource, from donor to acceptor. A competitive market mechanism in human organs is believed to improve the current kidney shortage situation. On the other hand, many critics worry that establishing a kidney market will damage the liberties of human. For example, they worry that a kidney market will enable exploitation of the desperation of the poor. The issue of kidney market is highly controversial. I appreciate the premium function of the market that enables human to allocate our rare resources. However, it is too hard to deny that the kidney market generates the pecuniary externality that damage human liberties. Therefore, I believe that believe that we should put the market of kidney on pending until we can eliminate its severe damage on human liberties. With hope, we are looking forward to having a new policy that can eliminate the limitations of the kidney market and can enable a better life for kidney-failure patients soon

A New Generation of Smart Multifunctional Additive for High-Temperature Lubrication in Metal Forming Processes

High-temperature lubrication plays a critical role in various engineering processes of hot metal forming (e.g. hot forging, hot rolling, hot extrusion…). It has been acknowledged that high energy efficiency, low material losses, and optimum product quality can be achieved by the application of effective lubricants. Although sodium-containing glass melts have proven themselves as the outstanding candidate lubricant for hot metalworking processes, they have reached their performance limit. In addition, the concern about the corrosion of sodium toward oxide scale is also highlighted. The current study not only puts an effort into improving the lubricity of the existing melt lubricants but also concentrates on the formulation of the lubricant package for high-temperature manufacturing processes. Particularly, the development of the novel multifunctional lubricant additives from the existing solid lubricants is at the heart of the research activities