*1.2. Surficial Geology*

The Izok Lake region was most recently glaciated during the Wisconsinan [32]. Regional surficial mapping in the Izok Lake region was carried out by Stea et al. [33], with large-scale ice flow reconstructions compiled by Dyke and Prest [34] and Dyke [35]. Recent ice flow indicator mapping in the region by Paulen et al. [36] built on the previous work to elucidate four ice flow phases that affected the region. Of these, an older southwest ice flow and younger northwest ice flow were determined to be responsible for the formation of most local glacial landforms and the palimpsest glacial transport of mineralized debris down ice [11,18]. These ice flows deposited a till cover that is relatively thin (<3 m thick) and consists mainly of silty sand till. The Izok Lake region is a permafrost terrain and, therefore, it is not practical to dig to appropriate till horizons by hand. All samples were collected at the surface from frost boils, small circular periglacial features formed by cryoturbation that bring till material from depth to surface [37].

The GSC carried out a reconnaissance-scale till geochemical survey in the Point Lake region, including the Izok Lake area, but geochemical analysis of the <0.002 mm and <0.063 mm till fractions did not indicate the presence of the mineralization at Izok Lake [38]. In 2009, a till geochemical survey was carried out around the Izok Lake deposit [17] along with a detailed bedrock and till indicator mineral survey. The <63 μm fraction of till, analyzed by aqua regia/inductively coupled plasma mass spectrometry (ICP-MS), yielded elevated values for Zn (<346 ppm), Cu (<322 ppm), Pb (<392 ppm), Fe (<1880 ppm), Ag (<1411 ppb), Cd (<1.36 ppm), Bi (<5.12 ppm), Hg (<247 ppb), Se (<0.5 ppm), In (<0.28 ppm), and Tl (<0.20 ppm) up to 6 km down ice to the northwest [11]. Also in 2009, a gossan containing sphalerite and referred to as the West Iznogoudh (WIZ) showing (Figure 2; [27]) was sampled. Oviatt [39] reported elevated contents of Zn, Ag, Cu, Hg, and Bi in the <63 μm fraction of till collected in the vicinity of the showing.

In addition to the till geochemical samples, bulk (10–15 kg) till and bedrock (1 kg) samples were collected around the Izok Lake deposit, concentrated to produce HMC and the >250 μm size fraction was examined for indicator minerals. That study identified gahnite, staurolite, chalcopyrite, sphalerite, pyrrhotite, and pyrite as indicator minerals. Gahnite dispersal was identified to be the broadest and farthest down ice of all of the indicator minerals identified, extending more than 40 km to the northwest with an older component to the southwest [11,18]. Significant abundances of sulfide minerals (chalcopyrite, galena, sphalerite, pyrite) were identified in the coarse fraction of only the most proximal down ice till sample to mineralization. Axinite, a potential indicator of hydrothermal alteration, was identified in bedrock thin sections and HMC, but was not identified in till HMC due to its lack of distinguishing visual characteristics [18,31].

**Figure 2.** Location of the four till samples used in this study. Arrows indicate relative ice flow chronology (1 = oldest) and vigor (arrow width) of flow events. Colored polygons depict the glacial dispersal fan for gahnite in the non-ferromagnetic 250–500 μm fraction of till heavy mineral concentrate (HMC), as interpreted by McClenaghan et al. [1]. Yellow polygon represents dispersal by the NW ice flow; blue represents dispersal by the older SW ice flow, and the question-marked border represents the terminal sampling distance beyond which data is not available.

#### **2. Materials and Methods**

Four till samples collected by Hicken et al. [18,31] were chosen for use in this study. They were selected based on their locations relative to mineralization and the indicator minerals identified in their coarse fraction of HMC, in particular gahnite. The four sample locations are shown in Figure 2, along with the gahnite dispersal fan identified by McClenaghan et al. [11]. Sample 09-MPB-060, located 1 km up ice of mineralization, was the farthest-up ice sample available, and was chosen to represent background values compared to down ice sample locations. However, this up ice sample site is still within the hydrothermal alteration halo surrounding the Izok Lake deposit [22], and may not represent true regional background for certain alteration indicator minerals. Sample 09-MPB-058, located 500 m down ice (west) of mineralization, was the only sample with a significant abundance of sulfide indicator minerals identified in the coarse fraction [18,31]. It is the most proximal down ice sample chosen for this study. Sample 09-MPB-075, located 3 km down ice of mineralization, represents the intermediate down ice sample chosen for this study. Previous work identified gahnite in the coarse fraction HMC of these till samples. Sample 12-MPB-902, located 8 km down ice of mineralization, represents the most distal down ice sample chosen for this study.

#### *2.1. Preparation of Heavy Mineral Concentrate (HMC) in Previous Geological Survey of Canada (GSC) Study*

In 2009, the four GSC till samples were processed to recover >3.2 SG HMC at Overburden Drilling Management Limited (ODM), in Ottawa, ON, Canada. Density concentration was carried out using a combination of wet screening and shaking table, followed by heavy liquid separation at 3.2 SG, acid-washing, and ferro-magnetic separation to produce coarse (>250 μm) non-ferromagnetic HMC (>3.2 SG) fraction. This fraction was visually examined, and indicator minerals were counted with results reported by Hicken [18] and McClenaghan et al. [11]. The archived byproduct of the sample

processing was the non-ferromagnetic <250 μm fraction. It is this fraction that forms this basis of the study reported here (Table 1).

**Table 1.** Sample processing weights indicating the original mass of bulk till sample prior to heavy mineral concentrate (HMC) production, the individual mass of each size fraction following sieving of the <250 μm HMC, and the mass of <250 μm HMC lost during sieving.

## *2.2. Sieving Methods*

The<250 μm HMC fraction of the four till samples was dry-sieved at the Queen's University Facility for Isotope Research (QFIR, Kingston, ON, Canada) into four smaller size fractions: (1) 185–250 μm, (2) 125–185 μm, (3) 64–125 μm, and (4) <64 μm. The sieving was carried out using single-use, nylon-screened sieves following the procedures developed by Lougheed et al. [40]. Table 1 contains the masses of <250 μm HMC prior to sieving, the masses of each resultant size fraction, and the mass loss of HMC material as a result of sieving.

#### *2.3. Epoxy Mounting of Mineral Grains*

The grain mounting method used in this study was modified after Blaskovich [41]. In our study, the entire mass of each of the 16 subsamples was mixed with vacuum-evacuated epoxy and poured into a 2.54 cm diameter plastic ring mold. Each ring mold was immediately placed into a vacuum chamber under full vacuum for 5 min. Vacuum impregnation eliminated air bubbles from liquid epoxy and drew epoxy into void spaces in mineral grains, maximizing the adhesion between epoxy and grains [42]. Following removal from the vacuum chamber, the mounts were allowed to cure for 24 h. The resulting grain mount was trimmed and vertically quartered using a Raytech Jemsaw 45 (Raytech Industries, Middletown, CT, USA) fitted with a diamond-impregnated blade. One quarter of each mount was archived. The other three quarter-pieces were remounted into a single plastic ring mold and set with epoxy (Figure 3) and cured for 12 h. Thus, one new epoxy mount containing three quarter slabs was prepared for each of the 16 subsamples. After polishing to 1 μm, these three slabs in the secondary mount were used for MLA analysis and examination of any settling effects or gradients that developed during mixing with epoxy and curing of the primary mount. Following polishing, the mounts were carbon coated using a Denton Vacuum Desk V carbon-coater (Denton Vacuum LLC, Moorestown, NJ, USA).

Grain mount preparation took ~30 min, followed by 12 h of curing time. Several samples were prepared simultaneously, with the limiting factor being the number of mounts that can be placed in the vacuum chamber.

**Figure 3.** Mounting schematic displaying the basal surface of the two mounting stages. The primary grain mount was quartered, and three quarters were reoriented and made into a second mount to display one basal surface and two cross-sectional surfaces for analysis. Cross-sectional surfaces are indicated by the black grey bar in left pane of figure.


**6.2. Feedback control for a model with cubic spring**

56 Nonlinearity, Bifurcation and Chaos – Theory and Applications

The system (18) can be represented as follows:

3 3

deviations as:

where

1 2

*e e*

*ae x ax*

2 2 2

*pe x px u*

3 3 11 1

Representing the system (24) in the form:

() ()

0

frequency equal to ( ), then:

3

*ay ay a y*

*d e p u y ry by cy g y*

*x x*

Replacing (19) in (18) and defining the deviation from the desired trajectory as:

*e*

2 2 1 11 1 22 88

with *u uF u* , and the feedback control: *u Ke* . The system (23) can be represented in

0 1 0 () () 1

88 33 11 1 11 1

Defining the desired trajectory as the periodic orbit, with amplitude less than (a) and

Considering the parameters values: 1; r 0.1 ; b 0.05 ; c 0.35 ; d 4/27 ; e 0.0001 ;

2 2 2

11 1 2 2

0

*g x gx u e e b r*

3 3

*gx gx d d*

*e e pe x px ae x ax ae x ax*

*ddee e re be c e x cx*

1 1 2 2

*ce x x*

g 0.2 ; p 0.005 e a 1.6 the matrices A and B, are given by:

*e e*

2 8 3 cos

*ae x ax ae x ax*

11 1 11 1

*e Ae g x g x Bu* () () (24)

(25)

*ae x ax*

11 1

*x t* 1.3sin( ) (26)

(22)

(21)

(23)

Considering the following parameters: 0.14668 , 0.17602 *b* , 2.6364 , 2.5 *z* , 1*a* 1 , 2*a* 14.5 , and the control *U* in (16) results:

$$\begin{aligned} \dot{\mathbf{x}}\_1 &= \mathbf{x}\_2\\ \dot{\mathbf{x}}\_2 &= -a a\_1 \mathbf{x}\_1 - \beta a\_2 \mathbf{x}\_1^3 - \frac{b}{\left(\mathbf{z} + \mathbf{x}\_1\right)^2} + \delta \sin b + \mathcal{U} \end{aligned} \tag{28}$$

where: *U uu* , *u* is the feedback control, *u* is the feedforward control, given by :

$$
\tilde{\mu} = \dot{\tilde{\mathbf{x}}}\_2 + aa\_1 \tilde{\mathbf{x}}\_1 + aa\_2 \tilde{\mathbf{x}}\_1^3 + \frac{b}{\left(\mathbf{z} + \tilde{\mathbf{x}}\_1\right)^2} - \delta \sin b \tag{29}
$$

Replacing (29) in (28) and defining the deviation from the desired trajectory as:

$$y = (\mathbf{x} - \tilde{\mathbf{x}}) \tag{30}$$

where *x* is the desired orbit, and rewriting the system in deviations, results:

$$\begin{aligned} \dot{y}\_1 &= y\_2\\ \dot{y}\_2 &= -aa\_1y\_1 - aa\_2\left(y\_1 + \tilde{\mathbf{x}}\_1\right)^3 + aa\_2\tilde{\mathbf{x}}\_1^{-3} - \frac{b}{\left(z + y\_1 + \tilde{\mathbf{x}}\_1\right)^2} + \frac{b}{\left(z + \tilde{\mathbf{x}}\_1\right)^2} + u \end{aligned} \tag{31}$$

Considering the system (31) in the following way:

$$
\dot{y} = Ay + g(\mathbf{x}) - g(\tilde{\mathbf{x}}) + Bu\tag{32}
$$

On an Overview of Nonlinear and Chaotic Behavior and

Their Controls of an Atomic Force Microscopy (AFM) Vibrating Problem 59

**Figure 13.** (a): Tip displacement without control (b): Tip Displacement with control

**Figure 14.** Microcantilever oscillatory behavior. Source: (Bueno et al., 2011).

In the dynamic mode the microcantilever is deliberately vibrated. The Amplitude Modulated AFM and the Frequency Modulated AFM are the most important techniques. In both AM-AFM and FM-AFM the amplitude and frequency of the microcantilever are kept constant by two control loops. The AGC (Automatic Gain Control) and the ADC (Automatic Distance Control). The AGC controls the amplitude of oscillation and the ADC controls the frequency by adjusting the distance between tip and sample. The oscillatory behavior of the

(a) (b)

In the FM-AFM the control signal of the AGC loop is used to generate the dissipation images and the ADC control signal is used to generate the topographic images. The FM-AFM improved image resolution and for surface studies in vacuum is the preferred AFM technique (Morita et. al., 2009; Bhushan, 2004). From Figure 15 it can be seen that the PLL generates the feedback signal for both control loops, therefore the PLL performance is vital to the FM-AFM. The PLL is a closed loop control system that synchronizes a local oscillator to a sinusoidal input. The PLLs are composed of a phase detector (usually a multiplier circuit), of a low-pass filter and of a VCO (Bueno et. al., 2010; Bueno et al., 2011), as it can be seen in Figure 16, and additionally, shows the PM and AM outputs used in the AFM system.

microcantilever is illustrated in Figure 14. The FM-AFM block is shown in Figure 15.

$$\begin{aligned} \text{where: } y &= \begin{bmatrix} y\_1 \\ y\_2 \end{bmatrix}; A = \begin{bmatrix} 0 & 1 \\ -aa\_1 & 0 \end{bmatrix}; B = \begin{bmatrix} 0 \\ 1 \end{bmatrix} \text{ and} \\\ \text{g(x)} &= \begin{bmatrix} 0 & 1 \\ -aa\_2\left(y\_1 + \tilde{x}\_1\right)^3 + aa\_2\tilde{x}\_1^3 - \frac{b}{\left(z + y\_1 + \tilde{x}\_1\right)^2} + \frac{b}{\left(z + \tilde{x}\_1\right)^2} \\\ \vdots \end{bmatrix}. \end{aligned} $$

solving the following equation:

$$
\mu = -R^{-1}B^T P \,\text{y} \tag{33}
$$

where *P* is a symmetric matrix, solution of the reduced Riccati equation:

$$PA + A^T P - PBR^{-1}B^T P + Q = 0\tag{34}$$

Defining the desired trajectory as:

$$
\tilde{\mathfrak{X}} = \mathfrak{Z}\cos(t) \tag{35}
$$

The matrices 0 1 0.14668 0 *A* , 0 1 *B* , and defining Q and R as 250 0 0 20 *Q* , *R* 0.1 , results after using the matlab(R) to obtain *u*:

$$u = -49.8535y\_1 - 17.3120y\_2\tag{36}$$

In Figure 13 it can observed the tip displacement with and without control.


**3. Results**

Mean total polyphenol content (TPC) was lowest in the cumin aqueous extract (103.0 ± 3.4 mg GAE/100 g of cumin powder) and highest in the tamarind aqueous extract (440.1 ± 13.3 mg GAE/100 g of tamarind pulp). Mean TPC of corn silk was 233.1 ± 2.2 mg GAE/100 g of dried corn silk.

Of the 18 volunteers enrolled in the study, 16 volunteers completed all nine test sessions. One volunteer only completed three test sessions, while another only completed five sessions. The baseline anthropometric and metabolic characteristics of the volunteers to indicate the profile of volunteers who completed the study are presented in Table 2. All participants had their fasted glucose concentration at screening visit of less than 6.0 mmol/L, except for one participant who had a concentration of 6.20 mmol/L and would therefore be considered as having impaired fasted glucose (IFG).

**Table 2.** Baseline anthropometric and metabolic characteristics.

#### *3.1. Postprandial Glycemic and Insulinemic Response to Control and Test Meals*

Figures 2 and 3 respectively show plasma glucose and insulin concentrations over time. As expected, mean plasma glucose concentration rose significantly above baseline fasting levels in the first hour after meal initiation, peaking at T30 and falling below baseline at T150 and T180 (Figure 2). Similarly, the mean plasma insulin concentration rose significantly above baseline fasting levels in the first 2 h after meal initiation, peaking at T45 and returning to baseline levels at T150 (Figure 3). There were no significant di fferences between the various treatments as compared with the control on postprandial glycemia, irrespective of the food form, evaluated using incremental areas under the curve for various time intervals (iAUC30, iAUC120, or iAUC180), as shown in Table 3. There were also no di fferences in the postprandial glycemic responses between the two di fferent forms (rice vs. drink) of consumption, irrespective of the test ingredients. Similarly, there were no significant di fferences in the influence of the various treatments as compared with the control on postprandial insulinemia as evaluated using incremental areas under the curve for various time intervals (iAUC30, iAUC120, or iAUC180). However, there was a significant increase (*p* < 0.01) in postprandial insulinemia (iAUC120 or iAUC180) when the test ingredients were consumed as a drink (D) as compared with the

same ingredients being cooked within rice (R), irrespective of the test ingredients. It should also be noted that the form × treatment interactions were not significant across all measures, as shown in Table 3.

**Figure 2.** Postprandial changes in plasma glucose concentration during various treatments. CSD12: corn silk drink 12 g; CSR12: corn silk rice 12 g; CSD24: corn silk drink 24 g; CSR24: corn silk rice 24 g; CUD: cumin drink; CUR: cumin rice; TAMD: tamarind drink; TAMR: tamarind rice.

**Figure 3.** Postprandial changes in plasma insulin concentration during various treatments. CSD12: corn silk drink 12 g; CSR12: corn silk rice 12 g; CSD24: corn silk drink 24 g; CSR24: corn silk rice 24 g; CUD: cumin drink; CUR: cumin rice; TAMD: tamarind drink; TAMR: tamarind rice.

a All analyses were done using the linear mixed effects procedure with compound symmetry covariance structure in SPSS. b Model testing effects of treatment overall, including control. c Model testing effects of form × treatment without control. Bold lettering indicates *p* < 0.05.

#### *3.2. Postprandial Changes in Blood Pressure during Control and Test Meals*

The postprandial changes in systolic and diastolic blood pressures are shown in Figures 4 and 5, respectively. There were no significant differences between treatments, irrespective of form or between forms, irrespective of treatments at baseline and in the total area under the curve (tAUC) of the postprandial systolic or diastolic blood pressure, as shown in Table 4.

**Figure 4.** Postprandial changes in systolic blood pressure during various treatments. corn silk drink 12 g; CSR12: corn silk rice 12 g; CSD24: corn silk drink 24 g; CSR24: corn silk rice 24 g; CUD: cumin drink; CUR: cumin rice; TAMD: tamarind drink; TAMR: tamarind rice.

**Figure 5.** Postprandial changes in diastolic blood pressure during various treatments. CSD12: corn silk drink 12 g; CSR12: corn silk rice 12 g; CSD24: corn silk drink 24 g; CSR24: corn silk rice 24 g; CUD: cumin drink; CUR: cumin rice; TAMD: tamarind drink; TAMR: tamarind rice.

**Table 4.** Baseline and total areas under the curve (tAUCs) of blood pressure over the postprandial period.


*3.5. Plastid Genome Assembly*

To assemble the Dasha plastid genome, we took the largest plastid contig (found based on similarity with *F. esculentum* ssp. *ancestrale* plastome) in the Unicycler assembly described above and extended it by Elloreas, which created a circular sequence after 50 iterations of extension. Elloreas was run with parameters "sequencing\_technology hifi\_pacbio", "minimum\_length\_of\_mapped\_read\_part 8000", "minimum\_read\_similarity 100%", "contig\_edge\_size\_to\_use\_for\_mapping 15000". To find possible misassemblies, we mapped PacBio reads by minimap2 with the "asm20" parameter and performed variant calling by FreeBayes v.1.3.0, searching for variants with a variant quality at least 40 supported by more than 50% reads. We found one misassembly in a poly-A region; that misassembly was introduced by Unicycler. An alternative variant (5 adenines instead of 4) was supported by 98.6% reads mapping to this position and we fixed the genome accordingly.

A pairwise alignment by the online version of NCBI BLAST showed that this assembly was collinear with the plastid genome of *F. esculentum* spp. *ancestrale*. The plastome sequence is deposited in NCBI Genbank under accession number MT364821.


**3. Narrowband metamaterial absorbers**

transmission coefficients. On the other hand, the highly conductive ground plane works as a perfect reflector, offering a phase delay of 180° to the electromagnetic wave reflecting on it.

**Figure 1.** Multiple reflections and interference model of metamaterial absorber. The yellow dashed line refers the

As shown in **Figure 1**, the front meta-layer resides at the interface between air and the dielectric substrate. The incident electromagnetic wave is partially reflected back to air with

reaching the metallic ground plane. The complex propagation constant inside the dielectric

tric substrate.  The corresponding reflection and trans-

that multiple reflections and transmissions exist inside the dielectric substrate, and the totally output energy at the left side of the metamaterial is the superposition of reflections of all

where the first term in the right is the reflection directly from the meta-layer, and the second term is the contribution of the superposition of the multiple higher-order reflections. As long

in those metamaterial absorbers with metallic grounds and also provide an alternative under-

It is worth noting that the above analysis is fully based on the assumption that the incident wave is normal to the metamaterial. For the case when an electromagnetic wave incident is

21(*ω*)*eiθ*21(*ω*)

*\_\_\_\_\_\_\_\_\_\_\_* 1 *+ r ~* 21*(ω)e*2*iβ*

~, the absorption spectrum of the metamaterial absorber could

. The interference theory can well explain the features observed

 and *t* ~ 21(*ω*) = *t*

and partially transmitted into the substrate with a

. The transmitted wave will propagate further until

is the wavenumber of free space, *d* is the thickness of

refers to the absorption in the dielec-

, respectively. It is worth noting

*~ ,* (5)

~, partial reflection

a reflection coefficient *r*

136 Metamaterials and Metasurfaces

transmission coefficient *t*

mission coefficients are *r*

as we know the total reflection *r*

be obtained by *A*(*ω*) = 1 −|*r*

~ = *β*1 + *i β*2 = √

substrate is *β*

orders:

the substrate, *β*1

~

resonator array. Reproduced from [47] with permission.

~ 12(*ω*) = *t*

\_\_

~

~(*ω*)| 2

12(*ω*) = *r*12(*ω*)*eiϕ*12(*ω*)

*εd k*0 *d*, where *k*0

21(*ω*) = *r*21(*ω*)*eiϕ*21(*ω*)

*r ~(ω) = r ~* 12*(ω) − t ~* 12*(ω) t ~* 21*(ω)e*2*iβ ~*

standing of the origin and underlying physics of metamaterial absorbers.

12(*ω*)*eiθ*12(*ω*)

represents the propagation phase, and *β*2

After direct mirror reflection and an additional propagation phase delay *β*

The first metamaterial absorber was theoretically investigated in 2006, consisting of an array of split ring resonators (SRRs)-backed with a resistive sheet [49]. The incident wave is parallel to the SRR plane with magnetic field being perpendicular to the SRR array. Such an SRR array is placed on a resistive sheet having a resistance of 377 Ω for impedance matching with free space, similar to a Salisbury screen. Both the reflection and transmission are below −20 dB at the vicinity of 2 GHz as numerically found. This is due to the strong resonances in this structure, where nearly perfect absorption was achieved at this frequency. However, due to the standing arrangement of the SRR array, this structure is not of low profile as compared with planar structures, which also increase its complexity in the manufacture. The bandwidth of absorption is also very limited. Nevertheless, the design of this metamaterial absorption motivates further research in these kinds of absorbers.

In 2008, Landy et al. [29] proposed a planar sandwiched structure that consists of electric ring resonators and cut wires separated by an FR-4 substrate, as shown in **Figure 2**. This is the first-reported metamaterial absorber with a planar and deeply subwavelength structure. The absorptivity observed is as high as 96% at 11.65 GHz in simulation and 88% at 11.5 GHz in experiment. The relative bandwidth of full width half maximum (FWHM) is around 4%. The front electric ring resonators couple strongly to the incident electric field and contribute electric response, while the circulating flow of antiparallel surface currents at the front and back metallic layers contributed a magnetic response. The absorption intensity and frequency could be controlled by adjusting the geometric parameters of electric ring resonators or the

**Figure 2.** (a) Unit cell of the first planar metamaterial absorber, (b) simulated reflection, transmission, and absorptance at microwave frequency. Reproduced from [29] with permission.

**Figure 3.** (a) Unit cell of dendritic metamaterial absorber and (b) simulated and measured absorptivity spectra. Reproduced from [50] with permission.

thickness of the substrate. Inspired by this pioneer work, great amounts of efforts have been devoted to the realization of metamaterial absorbers in different spectral ranges [30–40].

The initial metamaterial absorbers are polarization sensitive because of anisotropic unit cells [29, 51]. Planar metamaterial absorbers with highly symmetric structures were developed later, such as annular and circular patch arrays [52] and snowflake cells [53, 54]. In 2009, we developed a metamaterial absorber composed of dendritic unit cells [50]. As shown in **Figure 3(a)**, the periodical array of metallic dendritic cells is on one side of the FR-4 substrate and a full ground plane on the other side. It is shown in **Figure 3(b)** that both the simulation and experiment, in accordance with each other, show over 95% absorptivity at the frequency of 10.26 GHz. Such a metamaterial absorber has an excellence of planar isotropy, which shows equal absorption performance for an incident wave with arbitrary polarizations. When scaling down the size of the dendritic metamaterial absorber to the nanoscale, it is able to achieve perfect absorption in the optical regime, which was also confirmed with numerical simulation [50].

widely used for designing broadband metamaterial absorbers [59, 60]. In this section, some

**Figure 4.** Schematic view of the saw-toothed metamaterial absorber and its absorption spectrum. Reproduced from [39]

Electromagnetic Metamaterial Absorbers: From Narrowband to Broadband

http://dx.doi.org/10.5772/intechopen.78581

139

One of the most effective approaches for designing broadband metamaterial absorber is to stack resonant patches of different sizes. Cui et al. [39] proposed a multi-layer saw-toothed anisotropic metamaterial absorber at infrared wavelengths, as shown in **Figure 4**. Although such a metamaterial absorber is made of 21 layers of metal patches, its total thickness is still reasonably thin compared to the operating wavelength. Particularly, they demonstrated that the relative full absorptivity width at half maximum could be achieved to a figure as high as 86%. The ultra-broad bandwidth in such a layered metamaterial absorber is realized by the overlapping of multiple resonances according to the metal patches at different layers. Electromagnetic waves of higher frequencies are absorbed at the upper parts, while those of

Intrinsic high loss in dielectrics or semiconductors can also be utilized for designing wideband absorption in simple structures [59, 60]. For example, water is a highly lossy dielectric at microwave frequencies, whose permittivity could be well described by the Debye formula [62]. **Figure 5** shows the metamaterial absorber made of a water layer (with periodical holes) placed in a resin container, which is backed with a metallic ground plane at the bottom. With such a structure, Xie et al. [61] experimentally demonstrated an ultra-broadband absorption with absorptivity higher than 90% in the entire frequency band from 12 to 29.6 GHz. To figure out whether the broadband absorption in such a water metamaterial absorber is predominantly because of the intrinsic high loss of water, they also compared the absorption spectra for the case when the full water layer without holes and the case when the resin container is empty of water. As shown in **Figure 5(d)**, they found that the absorptivity of a full water layer

typical approaches for designing bandwidth-enhanced absorbers are discussed.

lower frequencies are trapped at the lower parts.

with permission.

Metamaterials, including those metamaterial absorbers, are commonly made of periodically arranged unit cells. The imperfection in manufacture will, to some extent, affects the performance of the metamaterial. This is particularly significant in an optical regime where the unit cells of the metamaterials are of nano-scale. To study this effect, the impact of disorder in the unit-cell arrangement in the metamaterial absorber was further studied [55]. It was found that absorptivity decreases and the absorption frequency gets red-shift as the unit cells become more disorderly. However, the metamaterial absorber with random unit cells still presents over 95% absorptivity for a reasonable level of disorder.


**2. Materials and method**

#### **2.1 Study areas**

We chose the survey sites based on the theoretical range of the primary vector of Zika virus, *Ae. aegypti,* as described by the CDC [8]*.* The surveyed area including

### *Survey for a Vector of Zika Virus and Two Other Mosquito Species in Four Ecoregions… DOI: http://dx.doi.org/10.5772/intechopen.94499*

most of Missouri south of the Missouri River as well as a few places north of the river on the western side of the state near and inside Kansas City, MO. This large region included four ecoregions: the Central Dissected Till Plains, the Osage Plains, the Ozark Highlands and the Mississippi River Alluvial Basin [6]. Only two surveyed counties were in the Central Dissected Till Plains, both near Kansas City. Most of the surveyed region lies within the Ozark Highlands, a region south of the Missouri River and covered with heavily forested hills. The western part of the surveyed region includes part of the Osage Plains region, a fertile prairie land with several streams and rivers. The southeastern portion of the surveyed region (the "Bootheel" of Missouri) includes parts of the Mississippi Alluvial Plain and is bordered by the Mississippi river. It supports large tracts of agriculture, including rice, soybean and cotton crops. The counties included in the survey (as well as the ecoregion for each) are depicted in **Figure 1**. Due to interest in potential vectors of human disease, the survey focused on locations near human habitations with many artificial containers, especially automobile salvage yards, used tire shops, and cemeteries. We also collected larvae from these sites and those data will be reported elsewhere. We resurveyed some sites as many as six times during three summers. Trapping occurred between June 3 and September 23 in 2016, between July 17 and October 29 in 2017, and between June 19 and August 19 in 2018.

We used three types of traps: the Fay-Prince Omnidirectional trap, the BG Sentinel trap and the Centers for Disease Control miniature light trap. All traps were baited with approximately five pounds of dry ice in a plastic cooler with a hole in the bottom to let the gas disperse, but the BG Sentinel trap also used a

#### **Figure 1.**

*Missouri counties where mosquito survey was performed are shaded gray (summers 2016–2018) (counties noted with a 1 are in the dissected till plains ecoregion. Those noted with a 2 are in the Osage Plains Ecoregion. Counties noted with a 3 are in the Ozarks Highlands ecoregion and those noted with a 4 are in the Mississippi River Alluvial Plain ecoregion).*

commercial lure (BG Lure) as it was designed to do. We placed the traps with baits on the sites in early afternoon and retrieved them in late morning. All traps were at least 50 paces apart from other traps. Trap contents were placed in a large cooler with a small amount of ice, then transported to the laboratory in Springfield, Missouri, where all mosquitoes were killed by freezing. Laboratory workers then pinned the female specimens and identified them microscopically using dichotomous keys in Darsie and Ward [9] and Burkett-Cadena [10].