Akhil+Jariwala

Written By: Santhi Ani Joseph, Matthieu Lancry, Bertrand Poumellec, Guy Dhalenne and Romuald Saint Martin http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TJ6-4V2HJPK-1&_user=1400827&_coverDate=02%2F01%2F2009&_alid=883010340&_rdoc=9&_fmt=high&_orig=search&_cdi=5302&_docanchor=&view=c&_ct=258&_acct=C000052589&_version=1&_urlVersion=0&_userid=1400827&md5=6c12321765753cb05698c068008f669d
 * Photonic crystal-like material synthesized by self-organization**

In this article, researchers from France analyzed the properties of a photonic crystal created by self-organization. A photonic crystal is a crystal that only allows certain wavelengths of light to pass through. It is the analog of a semiconductor for light. Wavelengths that can travel through are called modes and wavelengths that cannot travel through are in the photonic band gap. The other wavelengths are filtered out by the dielectric matrix The material synthesized has a distribution of quasi-periodic silica fibers in a monocrystalline matrix. Conventional methods for preparation of PC are usually based on microfabrication or holographic techniques. The former technique, also referred as top–down fabrication, involves several steps like, (1) etching a layer of holes into a high-index substrate (2) filling these holes with a material of different dielectric constant (insulation) and (3) growing another layer of high-index material on top of this, repeating the processes and finally removing the filling material to get the desired structure. This is the typical assembly method of a photonic crystal. On the contrary, we make use of self-assembling, exploiting the natural tendency of the microscopic colloidal particles to self-assemble into an ordered crystalline structure. This also enables us to produce long crystals of the order of several centimeters. We first synthesize CuGe1−//x//Si//x//O3, which is a monocrystal containing ordered glass fibers. To realize a material resembling PC, we then try to remove the glass fibers from the composite material by chemical etching and thus enhance the refractive index difference. The essential idea of the experiment was to see if an optical fiber photonic crystal could be recreated. The goal was to etch out the fibers from the crystalline matrix, using HF acid, and thus obtain a higher refractive index difference (.32 to .77) between the two dielectric phases. The group finished their work by performing optical microscopy and a SEM analysis of the photonic crystal resembling structure. A thin-cleaved slice of the sample (of thickness 0.5 mm) was taken for the experiment. It was immersed in 20% HF acid for 30 min and was observed under the optical microscope. There is significant difference in the structure of the sample after the procedure. Apparently, the surface of the material has been cleaned and the etched sample reveals lamellar structures around the fibers. The SEM analysis showed that, whereas before, the fibers themselves had circular cross section, after their removal its location assumes a rhomboid shape. One might be lead to think that there is a preferential direction along which the etching took place faster, which is the direction of the minor axis of the crystal. It is the surface tension of the fibers while in liquid form that enabled them to assume circular cross section. When the fibers are removed, the tension releases, and the surrounding matrix takes the shape decided by its crystalline properties.

**The effect of Pb and other elements found in recycled polypropylene on the manufacturing of lead-acid battery cases.**
 * Polymer Testing.** Volume 26, Issue 8, December 2007, Pages 1001-1014. E.E. Ferg, N. Rust

When lead acid batteries run out of voltage, the plastic is melted and recycled. The polypropylene is recovered by heating and remolding into the new and desired shape. However, impurities left in the battery could affect future products. This study showed that a significant amount of lead-containing particles in the form of lead dioxide and lead sulfate remain in the recycled plastic, and are evenly distributed throughout the polymer matrix. This is an issue because if the polypropylene is ever to be incinerated, the lead molecules are small enough to be shot up into the air.

Polypropylene is used in lead acid battery because of its unique properties. These include: a wide temperature range up to eight degrees Celsius, chemical resistance to acid, fuel, oils and antifreeze; physical shock; and good elasticity. Strict legislation began to regulate the use of polypropylene in automobile batteries because of the containment of heavy metals like lead. When the crushed PP is separated from the other components of the lead-acid battery, the chips are extensively washed in order to eliminate any traces of lead-containing particles. Nevertheless, lead and other heavy metal trace elements remain on the batter coating.

The authors of this article used X-ray fluorescence (XRF), which use X-ray tubes or radioactive isotopes to excite trace elements in a bulk matrix for their quantitative determination at concentrations levels as low as 10 ppm. X-rays are shot at the crystal lattice and they excite inner electrons of specific types of atoms. When the outermost electrons return back to fill the unstable inner shells, the levels of energy can be measured so the amount of a variety of atoms can be measured. The quantification of Pb and Ca in recycled Polypropylene was done by comparing the results obtained by X-ray Fluorescence analysis to a standard empirical technique of sample digestion and measuring the elemental concentration using Inductively Coupled Plasma. In ICP, atoms are heated to a very high temperature, and the intensity of the emission spectra are measured to quantify the amount of atoms in each sample. Pre-weighed samples were ashed in a furnace at 500 1C for 4 h, after which the residue was digested with a mixture of nitric and hydrochloric acid. The samples were then filtered and diluted with deionized water. Standards of the elements analyzed (Pb and Ca) were prepared from 1000 ppm analytical grade stock solutions with the same acid concentration used for the preparation of the samples. Samples and standards were then analyzed on a Perkin-Elmer Sciex ELAN 6100 ICP-MS analyzer.

The PP samples for the study were prepared from a mixture of recycled and virgin PP pellets that were sourced from two different recycling suppliers.6 different samples were made, ranging from 0 to 100% ratio of recycled to virgin material.

Accurate quantification of the Pb (and other elements) by XRF is possible by preparing a range of suitable standards using wax as a matrix. The direct correlation of the elements to another technique such as ICP, or Inductively Coupled Plasma Mass Spectrometry or ICP-MS, an analytical technique used for elemental determinations. It is influenced by the batch sample, which could have comparatively different additive concentrations. Care needs to be taken to ensure that the standard sample is completely homogenous with the added elements and all possible interferences are considered.

The scientists also looked at old battery casings under a transmission electron microscope and found that small crystalline balls of PbO2 on the order of less than a micrometer could be found stuck on the casing, indicating that the cleansing process was not complete. They also tried to see if any of these molecules produced vapors during the heating and remolding phase of recycling, but no lead vapors were found using a Plumbtesmo lead sensitive paper.

The results showed that the actual amount of lead in 100% recycled material can be as much as 1 ppt, as calcium can be as high as 3.5 ppt.

In conclusion, this experiment showed that lead oxide and lead sulfate remain on battery casings after cleaning and remolding. Other elements such as Ca, Ti, Br, Fe, Cr and Zn found in recycled PP, originate from a variety of fillers, additives, stabilizers, impurities and flame-retardants that are used in the battery case manufacturing. In the future, the amount of times the polypropylene in a specific battery casing has been recycled can be gauged by analyzing the content of lead.   http://www.pnas.org/content/99/23/14795.full.pdf+html  In the cell cycle, damaged DNA is detected by sensor proteins and is relayed to downstream effectors leading to cell cycle arrest, activation of DNA repair processes and apoptotic cell death depending on the context. Checkpoint Kinase 1 (Chk1) is a gene that is found in a variety of organisms, ranging from yeast to mice. Kinases transfer phosphate groups from high energy molecules in a process called phosphorylation. Chk1 is an essential part of the DNA damage checkpoint and the DNA replication checkpoint in mice. Cells lacking Chk1 demonstrate defective coping mechanisms with __DNA replication blocks__ and damaging agents. Prior evidence suggested that Chk1 deals with the __G2 checkpoint__ in human cells because Chk1 inhibitors given to cells stop all G2 checkpoint functions. In humans, fission yeast, and //Xe//, Chk1 has been proposed to regulate the G2 checkpoint by phosphorylating the Cdc25C protein phosphatase on residue(s) that facilitate the binding of 14-3-3 proteins (5, 15–18). In addition, human Chk1 has been proposed to regulate the stability of the Cdc25A protein phosphatase in UV-damaged cells, but does not react to IR damaged cells. In this article, scientists investigated the importance of Chk1 in the cell division cycle both with and without checkpoint activation.Chk1 was detected in a western blot by the presence of monoclonal or polyclonal antibodies.  Endogenous Cdc25A was immunoprecipitated and immunoblotted with Ab-3. Before radiating the cells, HeLa cells were mocktransfected or transfected with duplex siRNAs to destroy the Chk1 concentration in certain cells. The siRNA molecules damage the RNA in a process called RNA interference. Thirty-six hours later, cells were mock-irradiated or exposed to 6 Gy IR from a 60Co source. Cells were stained with 30 microg/ml of propidium iodide and for phospho-histone H3 1 hour later. Another set of RNAi experiments were run to see if Chk1 is required for the IR induced G2 checkpoint. Normal cells were contrasted to the siRNA treated cells to see if the cells would still enter mitosis.  The results of the experiment indicated that after IR radiation, Chk1 cells had Cdc25A that did not remain stable, and Chk1 deficiency resulted in a stable Cdc25A stability. Chk2 was also measured along with Cdc25A and it was found that, while unaltered in normal Chk1-siRNA cells, it was fully phosphorylated in cells treated with IR. It was also found that **Reducing Cdc25A **Levels Partially Restores the G2–DNA Damage Checkpoint in Chk1-Deficient Cells. Loss of Chk1 interferes with the ability of cells to eliminate Cdc25A after IR (Fig. 2), and loss of Chk1 causes bypass of the IR-induced G2 checkpoint (Fig. 1). They tested to measure the effect by seeing if the G2 checkpoint could be resumed by lowering the Cdc25A checkpoint. They measured the effectiveness of the checkpoint using electrophoresis and comparing this to the level of the dose of the IR. 
 * Disruption of the checkpoint kinase 1 **<span style="font-size: 12pt; font-family: "Times New Roman","serif";">_**cell division cycle 25A pathway abrogates ionizing radiationinduced S and G2 checkpoints**
 * <span style="font-size: 12pt; font-family: "Times New Roman","serif";">Hui Zhao*, Janis L. Watkins*, and Helen Piwnica-Worms*†‡§ **<span style="font-size: 12pt; font-family: "Times New Roman","serif";">