Effect of Temperature, Catalyst Concentration and Time, on Polylactic Acid Production from Sisal Boles Juice by Ring Open Polymerization

Polylactic acid (PLA) is a biodegradable and renewable alternative to non-biodegradable petrochemical-based polymers that is environmentally friendly and green. PLA can be made from a variety of agricultural wastes that contain sugars, such as sisal boles. This study aimed at analysing the possibility of producing PLA from lactic acid (LA) produced from sisal bole. A 2n factorial design was used to analyse the effects of temperature (160-180ºC), time (1-2 hrs) and tin octoate catalyst concentration (0.025-0.05%) on the PLA yield during polymerization. Minitab Version 20.2.0 was used to design the experiment and analyse the effects on the responses through ANOVA. It was possible to produce 0.73±0.05 g of lactide per g of sisal bole LA used. More than 99% conversion of lactide into PLA was done for 2 hrs when the system temperature was 180ºC regardless of the catalyst ratio used. Temperature and time significantly affected the yield with p-values of less than 0.05 at 95% confidence level. The current findings support sisal bole juice as an alternative feedstock for LA production, a precursor for PLA. The use of sisal bole (SB) waste will protect environment by using waste biomass as an opportunity to participate in a global move to produce biobased plastics and promote the ban on the use of petrochemical-based plastics in packaging

Nested recursions with ceiling function solutions

Consider a nested, non-homogeneous recursion R(n) defined by R(n) = \sum_{i=1}^k R(n-s_i-\sum_{j=1}^{p_i} R(n-a_ij)) + nu, with c initial conditions R(1) = xi_1 > 0,R(2)=xi_2 > 0, ..., R(c)=xi_c > 0, where the parameters are integers satisfying k > 0, p_i > 0 and a_ij > 0. We develop an algorithm to answer the following question: for an arbitrary rational number r/q, is there any set of values for k, p_i, s_i, a_ij and nu such that the ceiling function ceiling{rn/q} is the unique solution generated by R(n) with appropriate initial conditions? We apply this algorithm to explore those ceiling functions that appear as solutions to R(n). The pattern that emerges from this empirical investigation leads us to the following general result: every ceiling function of the form ceiling{n/q}$ is the solution of infinitely many such recursions. Further, the empirical evidence suggests that the converse conjecture is true: if ceiling{rn/q} is the solution generated by any recursion R(n) of the form above, then r=1. We also use our ceiling function methodology to derive the first known connection between the recursion R(n) and a natural generalization of Conway's recursion.Comment: Published in Journal of Difference Equations and Applications, 2010. 11 pages, 1 tabl

New approach to 3D electrostatic calculations for micro-pattern detectors

We demonstrate practically approximation-free electrostatic calculations of micromesh detectors that can be extended to any other type of micropattern detectors. Using newly developed Boundary Element Method called Robin Hood Method we can easily handle objects with huge number of boundary elements (hundreds of thousands) without any compromise in numerical accuracy. In this paper we show how such calculations can be applied to Micromegas detectors by comparing electron transparencies and gains for four different types of meshes. We demonstrate inclusion of dielectric material by calculating the electric field around different types of dielectric spacers

Plan optimization for stereotactic radiotherapy

Cancer is one of the leading causes of death in the world. Next to surgery and chemotherapy, radiotherapy is one of the most used treatment modalities for cancer. About 50% of the patients with cancer will be treated with radiotherapy during the management of their disease. In radiotherapy, ionizing radiation is used to kill proliferating tumor cells. As an unwanted (but sometimes unavoidable) side-effect, delivery of ionizing radiation to the patient may also lead to damage to healthy tissues. Generally, the total dose is delivered in a number of daily fractions. In between fractions, the healthy tissues can often more effectively repair part of the damage than tumors. Hence, the cumulative damage to tumor tissue is higher than for normal tissue when exposed to the same total dose in a large number of fractions. For most tumors and healthy tissues, this differential repair effect is enhanced with higher numbers of fractions

Recovery of the persistent current induced by the electron-electron interaction in mesoscopic metallic rings

Persistent currents in mesoscopic metallic rings induced by static magnetic fields are investigated by means of a Hamiltonian which incorporates diagonal disorder and the electron-electron interaction through a Hubbard term ($U$). Correlations are included up to second order perturbation theory which is shown to work accurately for $U$ of the order of the hopping integral. If disorder is not very strong, interactions increase the current up to near its value for a clean metal. Averaging over ring lengths eliminates the first Fourier component of the current and reduces its value, which remains low after interactions are included.Comment: uuencoded gzipped tar file containing the manuscript (tex file) and four figures (postscript files). Accepted for publication in Solid State Communications. Send e-mail to: [email protected]

Statistical methods applied to composition studies of ultrahigh energy cosmic rays

The mass composition of high energy cosmic rays above $10^{17}$ eV is a crucial issue to solve some open questions in astrophysics such as the acceleration and propagation mechanisms. Unfortunately, the standard procedures to identify the primary particle of a cosmic ray shower have low efficiency mainly due to large fluctuations and limited experimental observables. We present a statistical method for composition studies based on several measurable features of the longitudinal development of the CR shower such as $N_{max}$, $X_{max}$, asymmetry, skewness and kurtosis. Principal component analysis (PCA) was used to evaluate the relevance of each parameter in the representation of the overall shower features and a linear discriminant analysis (LDA) was used to combine the different parameters to maximize the discrimination between different particle showers. The new parameter from LDA provides a separation between primary gammas, proton and iron nuclei better than the procedures based on $X_{max}$ only. The method proposed here was successfully tested in the energy range from $10^{17}$ to $10^{20}$ eV even when limitations of shower track length were included in order to simulate the field of view of fluorescence telescopes

Criptococosis meníngea en un paciente inmunocompetente: reporte de un caso y revisión de la literatura

ResumenLa criptococosis meníngea es una infección infrecuente en pacientes inmunocompetentes. Es de vital importancia realizar una adecuada historia clínica y exploración física para hacer un buen diagnóstico e iniciar un tratamiento lo antes posible, para prevenir complicaciones o secuelas de la misma. Nosotros reportamos un caso de un paciente del sexo masculino de 23años de edad que se presenta a consulta de neurología por cefalea intensa de tipo pulsátil holocraneana, acompañada de náuseas, que no cede ante el uso de analgésicos. Conforme progresaba la enfermedad, se añadían síntomas como vómito en proyectil, parestesias, alteraciones auditivas, disminución en la agudeza visual y cuadriparesia. Se hospitalizó para la realización de estudios complementarios, en los que se concluyó el diagnóstico de criptococosis meníngea. Los aspectos referentes a esta enfermedad, como epidemiología, etiología, diagnóstico, tratamiento y complicaciones, se discuten en este reporte de caso.AbstractThe cryptococcal meningitis is an infrequent infection in immunocompetent patients. It is vital to make an adequate history and physical examination to make a proper diagnosis and begin treatment as soon as possible to prevent complications or consequences thereof. We report a case of a male patient of 23years of age presenting to the neurology service because of an intense, throbbing headache accompanied with nausea that does not yield to the use of analgesics. As the disease progressed, other symptoms presented like projectile vomiting, paresthesias, hearing impairment, decreased visual acuity and quadriparesis. He was hospitalized for complementary studies which concluded the diagnosis of meningeal cryptococcosis. The aspects concerning this disease including epidemiology, etiology, diagnosis, treatment and complications are discussed in this case report

Monte Carlo Calculations for Liquid 4^4He at Negative Pressure

A Quadratic Diffusion Monte Carlo method has been used to obtain the equation of state of liquid $^4$He including the negative pressure region down to the spinodal point. The atomic interaction used is a renewed version (HFD-B(HE)) of the Aziz potential, which reproduces quite accurately the features of the experimental equation of state. The spinodal pressure has been calculated and the behavior of the sound velociy around the spinodal density has been analyzed.Comment: 10 pages, RevTex 3.0, with 4 PostScript figures include

Computed tomographic features of feline sino-nasal and sino-orbital aspergillosis

Feline upper respiratory tract aspergillosis (URTA) occurs as two distinct anatomic forms, sinonasal aspergillosis (SNA) and sino-orbital aspergillosis (SOA). An emerging pathogen, Aspergillus felis is frequently involved. The pathogenesis of URTA, in particular, the relationship between the infecting isolate and outcome, is poorly understood. Computed tomography was used to investigate the route of fungal infection and extension in 16 cases (SNA n=7, SOA n=9) where the infecting isolate had been identified by molecular testing. All cases had nasal cavity involvement except one cat with SNA that had unilateral frontal sinus changes. A strong association between the infecting species and anatomic form was identified. A. fumigatus infections remained within the sino-nasal cavity. Cryptic species infections were associated with orbital and paranasal soft-tissue involvement and with orbital lysis. These species were further associated with a mass in the nasal cavity, paranasal sinuses or nasopharynx. Orbital masses showed heterogeneous contrast enhancement, with central coalescing hypoattenuating foci and peripheral rim enhancement. Severe, cavitated turbinate lysis, typical of canine SNA, was present only in cats with SNA. These findings support that the nasal cavity is the portal of entry for fungal spores in feline URTA and that the route of extension to involve the orbit is via direct naso-orbital communication from bone lysis. Additionally, a pathogenic role for A. wyomingensis and a sinolith in a cat with A. udagawae infection are reported for the first time. Keywords: Aspergillus felis; Aspergillosis; Cats; Sino-nasal; Sino-orbita