Electromagnetic Field Control and Optimization Using Metamaterials

Transformation optics has shown the ability to cloak an object from incident electromagnetic radiation is possible. However, the material parameters are inhomogeneous, anisotropic, and, in some instances, singular at various locations. In order for a cloak to be practically realized, simplified parameter sets are required. However, the simplified parameters result in a degradation in the cloaking function. Constitutive parameters for simplified two-dimensional cylindrical cloaks have been developed with two material property constraints. It was initially believed satisfying these two constraints would result in the simplified cylindrical cloaks having the same wave equation as an ideal cloak. Because of this error, the simplified cloaks were not perfect. No analysis was done to determine all material parameter constraints to enable a perfect two-dimensional cylindrical cloak. This research developed a third constraint on the material parameters. It was shown as the material parameters better satisfy this new equation, a two-dimensional cylindrical cloak\u27s hidden region is better shielded from incident radiation. Additionally, a novel way to derive simplified material parameters for two-dimensional cylindrical cloaks was developed. A Taylor series expansion dictated by the new constraint equation leads to simplified cloaks with significantly improved scattering width performances when compared to previous published results. During the course of this research, it was noted all cloak simulations are performed using finite element method (FEM) based numerical methods. A Green\u27s function was used to accurately calculate scattering widths from a two-dimensional cylindrical cloak with a perfect electrically conducting inner shell. Significant time improvements were achieved using the Green\u27s function compared to an FEM solution particularly as the computational domain size is increased. Finally, cloaks are physically realized using metamaterials. Design of metamaterials has typically been done empirically. Shifts in S-parameter measurements and the resulting extracted constitutive parameters are used to determine the impact to resonant regions due to various geometries. A new way to design and possibly optimize unit cell metamaterials was investigated using an eigendecomposition to identify the cell resonances. Different structures were shown to have different resonances, and control of the resonant locations can lead to optimum designs

Controlling the Transmitted Field into a Cylindrical Cloak\u27s Hidden Region

Constitutive parameters for simplified cylindrical cloaks have been developed such that εzµθ and εzµr match those of the ideal cylindrical cloak. Although they are not perfect, simplified cylindrical cloaks have been shown to inherit many of the power-bending properties of the ideal cloak. However, energy is transmitted into simplified cloaks\u27 hidden regions. Here, we develop a constraint equation that can be used to determine how closely field behavior within the simplified cylindrical cloak matches that of the ideal cloak. The deviation from this controlling equation can be reduced by controlling the cloak\u27s parameter value, μθ As the deviation from our constraint equation is decreased, the field transmitted into the cloak\u27s hidden region is reduced, resulting in less energy impinging on the cloaked object. This results in a smaller scattered field due to the presence of the cloaked object. However, the resulting impedance mismatch at r = b results in a significant scattered field by the cloak itself. Thus, we have found when using cylindrical cloaks that satisfy the ideal values of εzµθ and εzµr for scattering width reduction, it is more important to have a matched impedance at r = b than to have a smaller field transmitted into the cloak\u27s hidden region. However, such cloaks\u27 scattering widths can vary significantly as a function of the object in the hidden region. A cloak with a matched impedance at r = b and that satisfies specific values for εzµθ and μ′θ performs reasonably well in terms of scattering width reduction in certain angular regions while being independent of the object in the hidden region. © 2008 Optical Society of America

Cooperative adsorption of carbon disulfide in diamine-appended metal-organic frameworks.

Over one million tons of CS2 are produced annually, and emissions of this volatile and toxic liquid, known to generate acid rain, remain poorly controlled. As such, materials capable of reversibly capturing this commodity chemical in an energy-efficient manner are of interest. Recently, we detailed diamine-appended metal-organic frameworks capable of selectively capturing CO2 through a cooperative insertion mechanism that promotes efficient adsorption-desorption cycling. We therefore sought to explore the ability of these materials to capture CS2 through a similar mechanism. Employing crystallography, spectroscopy, and gas adsorption analysis, we demonstrate that CS2 is indeed cooperatively adsorbed in N,N-dimethylethylenediamine-appended M2(dobpdc) (M = Mg, Mn, Zn; dobpdc4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate), via the formation of electrostatically paired ammonium dithiocarbamate chains. In the weakly thiophilic Mg congener, chemisorption is cleanly reversible with mild thermal input. This work demonstrates that the cooperative insertion mechanism can be generalized to other high-impact target molecules

Cooperative Adsorption of Carbon Disulfide in Diamine-Appended Metal– Organic Frameworks

Over one million tons of carbon disulfide are produced globally each year for an array of applications, and emissions of this highly volatile and toxic liquid, known to generate acid rain, remain poorly controlled. As such, materials capable of reversibly capturing this commodity chemical in an energy-efficient manner are of interest. Recently, we detailed a family of diamine-appended metal–organic frameworks capable of selectively capturing carbon dioxide through a cooperative insertion mechanism that promotes efficient adsorption–desorption cycling. We therefore sought to explore the fundamental ability of these materials to capture CS2 through a similar mechanism. Employing crystallography, spectroscopy, and gas adsorption analysis, we demonstrate that CS2 is indeed cooperatively adsorbed in N,N-dimethylethylenediamine-appended M2(dobpdc) (M = Mg, Mn, Zn; dobpdc4− = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate), via the formation of electrostatically paired ammonium dithiocarbamate chains. Notably, in the weakly thiophilic Mg congener, chemisorption is cleanly reversible with mild thermal input. Importantly, this work demonstrates that the hitherto CO2-specific cooperative insertion mechanism can be generalized to other high-impact target molecules.</p

Polioencefalomalacia em bovinos nos estados de Mato Grosso do Sul e São Paulo Polioencephalomalacia in cattle in the states of Mato Grosso do Sul and São Paulo

Trinta focos de polioencefalomalacia (PEM) foram diagnosticados no período de agosto de 1993 a outubro de 1997. Vinte e nove focos ocorreram no estado de Mato Grosso do Sul (MS) e um no estado de São Paulo (SP). Foram afetados bovinos de 4 a 84 meses de idade. A morbidade dos rebanhos afetados variou de 0,02% a 14,28% e a letalidade de 42,5% a 100%. A doença não apresentou uma sazonalidade e ocorreu em vários municípios do MS. Em todos os focos estudados os animais afetados eram criados em regimes de criação extensiva, com exceção de um foco. Os sinais clínicos observados foram exclusivamente nervosos e a evolução dos casos variou de 12 horas a 4 dias. A maioria dos animais tratados com tiamina e dexametasona recuperou-se. Histologicamente, as lesões consistiam de necrose laminar do córtex cerebral. Adicionalmente em 2 casos observaram-se hemorragias submeningeanas e corticais, e em 9 casos presença de infiltrado de eosinófilos. A dosagem de sódio no líquor apresentou-se elevada em um caso. A etiologia da PEM não está esclarecida, porém em alguns casos a intoxicação por cloreto de sódio/privação de água pode estar envolvida na etiologia da enfermidade. A PEM representa 4,78% dos casos de enfermidades de bovinos diagnosticadas no Laboratório de Anatomia Patológica da UFMS. Com bases nos resultados, verifica-se a importância da enfermidade no diagnóstico diferencial de outras doenças com quadro clínico neurológico no MS, principalmente a raiva, a meningoencefalite por herpesvírus bovino tipo 5 (HVB-5) e o botulismo.<br>Thirty outbreaks of polioencephalomalacia (PEM) were diagnosed from August 1993 to October 1997. Twenty nine occurred in the state of Mato Grosso do Sul and one in São Paulo. The disease affected cattle from 4 months to 7 years of age. Morbidity rates ranged from 0.02% to 14.28% and case fatalities from 42.5 % to 100%. The disease was not seasonal. All outbreaks occurred in cattle grazing Brachiaria spp, except one affecting feedlot cattle. Only neurologic signs were observed, and the course of the disease varied from 12 hours to 4 days in untreated cattle. Most animals treated with thiamine and dexamethazone recovered. Moderate cerebral edema was observed at necropsy. Cell changes were characterized by laminar necrosis and gitter cells. In two cases moderate cortical and submeningeal hemorrhages were observed. Nine cases had perivascular and submeningeal infiltrations by eosinophils. Sodium ion concentration of the cerebrospinal fluid was elevated in one case. The cause of PEM in the region was not determined, but the results suggest that in some cases sodium chloride intoxication/water deprivation could play a role in the etiology of the disease. PEM represents 4.78% of cattle disease diagnosed at the Pathology Laboratory of the Federal University of Mato Grosso do Sul

Impaired Limb Shortening following Stroke: What’s in a Name?

Difficulty advancing the paretic limb during the swing phase of gait is a prominent manifestation of walking dysfunction following stroke. This clinically observable sign, frequently referred to as 'foot drop', ostensibly results from dorsiflexor weakness.Here we investigated the extent to which hip, knee, and ankle motions contribute to impaired paretic limb advancement. We hypothesized that neither: 1) minimal toe clearance and maximal limb shortening during swing nor, 2) the pattern of multiple joint contributions to toe clearance and limb shortening would differ between post-stroke and non-disabled control groups.We studied 16 individuals post-stroke during overground walking at self-selected speed and nine non-disabled controls who walked at matched speeds using 3D motion analysis.No differences were detected with respect to the ankle dorsiflexion contribution to toe clearance post-stroke. Rather, hip flexion had a greater relative influence, while the knee flexion influence on producing toe clearance was reduced.Similarity in the ankle dorsiflexion, but differences in the hip and knee, contributions to toe clearance between groups argues strongly against dorsiflexion dysfunction as the fundamental impairment of limb advancement post-stroke. Marked reversal in the roles of hip and knee flexion indicates disruption of inter-joint coordination, which most likely results from impairment of the dynamic contribution to knee flexion by the gastrocnemius muscle in preparation for swing. These findings suggest the need to reconsider the notion of foot drop in persons post-stroke. Redirecting the focus of rehabilitation and restoration of hemiparetic walking dysfunction appropriately, towards contributory neuromechanical impairments, will improve outcomes and reduce disability

Allotransplantation for Patients Age ≥40 Years with Non-Hodgkin Lymphoma: Encouraging Progression-Free Survival.

International audience: Non-Hodgkin lymphoma (NHL) disproportionately affects older patients, who do not often undergo allogeneic hematopoietic cell transplantation (HCT). We analyzed Center for International Blood and Marrow Transplant Research data on 1248 patients age ≥40 years receiving reduced-intensity conditioning (RIC) or nonmyeloablative (NMA) conditioning HCT for aggressive (n = 668) or indolent (n = 580) NHL. Aggressive lymphoma was more frequent in the oldest cohort 49% for age 40 to 54 versus 57% for age 55 to 64 versus 67% for age ≥65; P = .0008). Fewer patients aged ≥65 had previous autografting (26% versus 24% versus 9%; P = .002). Rates of relapse, acute and chronic GVHD, and nonrelapse mortality (NRM) at 1 year post-HCT were similar in the 3 age cohorts (22% [95% confidence interval (CI), 19% to 26%] for age 40 to 54, 27% [95% CI, 23% to 31%] for age 55 to 64, and 34% [95% CI, 24% to 44%] for age ≥65. Progression-free survival (PFS) and overall survival (OS) at 3 years was slightly lower in the older cohorts (OS: 54% [95% CI, 50% to 58%] for age 40 to 54; 40% [95% CI, 36% to 44%] for age 55 to 64, and 39% [95% CI, 28% to 50%] for age ≥65; P < .0001). Multivariate analysis revealed no significant effect of age on the incidence of acute or chronic GVHD or relapse. Age ≥55 years, Karnofsky Performance Status <80, and HLA mismatch adversely affected NRM, PFS, and OS. Disease status at HCT, but not histological subtype, was associated with worse NRM, relapse, PFS, and OS. Even for patients age ≥55 years, OS still approached 40% at 3 years, suggesting that HCT affects long-term remission and remains underused in qualified older patients with NHL

A relational vulnerability analytic: Exploring hybrid methodologies for human dimensions of climate change research in the Himalayas

Vulnerability assessments are critical tools when exploring the Human Dimensions of Climate Change in the Global South. Additionally, Social Ecological Systems research utilizes such assessments to describe and predict potential spaces/tools of policy intervention. However, much of the assessment methodology fails to address the coupled structural processes underlying vulnerability and the experience of climate change. First, most scholarship does not operationalize mixed-methods research using plural epistemologies. Second, it fails to incorporate the communally produced knowledge of marginalized regional populations. Ultimately, power inequalities and their impact on vulnerability within complex adaptive systems, are overwhelmingly ignored. This project attempts to address these issues through a ‘Relational Vulnerability Analytic’ (RVA). We utilize a plural epistemological approach to construct an analytic that envisions the various relationships, processes and tools that need to be cultivated and managed in order to empower the community as co-producers of knowledge, while challenging the disciplinary bias in explorations of climate change risk and adaptation. Our method brings top-down spatial analysis tools, mathematical models, grounded ethnographic fieldwork and participatory feminist epistemologies into productive tension to reveal the sources of vulnerability and the agency of subjects, in rural Himalayan households. Additionally, we addresses the appeal for long term, collaborative, multi-dimensional research mobilization in the Himalayas. While the analytic is parameterized for the Himalayan region, it can be implemented in other regions with certain salient customizations. The project concludes that future efforts should be to operationalize this analytic for different regions and populations

Effect of Aging and Predonation Comorbidities on the Related Peripheral Blood Stem Cell Donor Experience: Report from the Related Donor Safety Study.

The development of reduced-intensity approaches for allogeneic hematopoietic cell transplantation has resulted in growing numbers of older related donors (RDs) of peripheral blood stem cells (PBSCs). The effects of age on donation efficacy, toxicity, and long-term recovery in RDs are poorly understood. To address this we analyzed hematologic variables, pain, donation-related symptoms, and recovery in 1211 PBSC RDs aged 18 to 79 enrolled in the Related Donor Safety Study. RDs aged &gt; 60 had a lower median CD34+ level before apheresis compared with younger RDs (age &gt; 60, 59 × 106/L; age 41 to 60, 81 × 106/L; age 18 to 40, 121 × 106/L; P &lt; .001). This resulted in older donors undergoing more apheresis procedures (49% versus 30% ≥ 2 collections, P &lt; .001) and higher collection volumes (52% versus 32% &gt; 24 L, P &lt; .001), leading to high percentages of donors aged &gt; 60 with postcollection thrombocytopenia &lt;50 × 109/L (26% and 57% after 2 and 3days of collection, respectively). RDs aged 18 to 40 had a higher risk of grades 2 to 4 pain and symptoms pericollection, but donors over age 40 had more persistent pain at 1, 6, and 12 months (odds ratio [OR], 1.7; P = 0.02) and a higher rate of nonrecovery to predonation levels (OR, 1.7; P = .01). Donors reporting comorbidities increased significantly with age, and those with comorbidities that would have led to deferral by National Marrow Donor Program unrelated donor standards had an increased risk for persistent grades 2 to 4 pain (OR, 2.41; P &lt; .001) and failure to recover to predonation baseline for other symptoms (OR, 2.34; P = .004). This information should be used in counseling RDs regarding risk and can assist in developing practice approaches aimed at improving the RD experience for high-risk individuals