Bottom Half Research Articles

Hydrodynamic Response Analysis of Combined Spar Wind Turbine and Fish Cage for Offshore Fish Farms

This paper is concerned with the hydrodynamic response of a novel offshore fish farm that combines a floating spar wind turbine and a fish cage (named as COSPAR for brevity). The open net steel cage is octagonal in shape with a partially porous wave fence at its top end to attenuate wave energy for a calm fish farming environment as well as to keep predators out. The deep draught spar is made from concrete for its bottom half and from steel for its top half. The spar carries a control unit and a 1[Formula: see text]MW wind turbine that provides the required power to operate the offshore salmon fish farm. The COSPAR fish cage has four catenary chains as mooring lines attached to mid length of the spar (outside the fish cage) so as to mitigate tension force in the mooring lines and to reduce the benthic footprint. ANSYS Design Modeler and Aqwa are used to perform the hydrodynamic response analysis of free-floating condition of COSPAR in the frequency domain and coupled analysis involving COSPAR and the mooring lines in the frequency domain and time domain. Environmental conditions, representing 5-year, 20-year and 50-year wave return periods with a constant current flow at an exposed fish farming site in Storm Bay of Tasmania, Australia, are adopted for the analyses. A comparison study is made against having a floating fish cage only (i.e. without the bottom half concrete of the spar) with four catenary chains attached to side vertical columns of the cage so that the fish cage behaves like a semi-submersible cage. Based on the comparison study, the COSPAR fish cage shows enhanced hydrodynamic responses in the following respects: (1) more stable motion responses in heave and pitch against wave and current forces, (2) less susceptible to the viscous damping when it is assumed by a linearized drag force of Morison elements in the frequency domain and (3) reduction of tension forces in the mooring lines. Interestingly, the pitch motion response of COSPAR fish cage in the frequency domain is in close agreement with the time domain result due to its greater pitching stiffness that reduces nonlinear effects from viscous drag and mooring interaction.

"Masking" our emotions: Botulinum toxin, facial expression, and well-being in the age of COVID-19.

BackgroundThe globally devastating effects of COVID‐19 breach not only the realm of public health, but of psychosocial interaction and communication as well, particularly with the advent of mask‐wearing.MethodsA review of the literature and understanding of facial anatomy and expressions as well as the effect of botulinum toxin on emotions and nonverbal communication.ResultsToday, the mask has become a semi‐permanent accessory to the face, blocking our ability to express and perceive each other’s facial expressions by dividing it into a visible top half and invisible bottom half. This significantly restricts our ability to accurately interpret emotions based on facial expressions and strengthens our perceptions of negative emotions produced by frowning. The addition of botulinum toxin (BTX)–induced facial muscle paralysis to target the muscles of the top (visible) half of the face, especially the corrugator and procerus muscles, may act as a therapeutic solution by its suppression of glabellar lines and our ability to frown. The treatment of the glabella complex not only has been shown to inhibit the negative emotions of the treated individual but also can reduce the negative emotions in those who come in contact with the treated individual.ConclusionsMask‐wearing in the wake of COVID‐19 brings new challenges to our ability to communicate and perceive emotion through full facial expression, our most effective and universally shared form of communication, and BTX may offer a positive solution to decrease negative emotions and promote well‐being for both the mask‐wearer and all who come in contact with that individual.

Release of unwanted flat-bodied fish from a horizontal-bar grid system as revealed through comparative fishing trials and underwater video observations

Grid systems separate fish species primarily through physical means: fish size and body shape. On Georges Bank off the northeast USA, many species of flounders are overfished, and their catch needs to be reduced. Flat-bodied skates are also often discarded. We tested a European style horizontal-bar grid system to reduce these flat-bodied low quota species in a trawl targeting the haddock (Melanogrammus aeglefinus), whose population is robust. The grid system consisted of 4 grid sections, two on each side, with horizontal bars 70 mm apart. The alternating tow method was used to compare the catch characteristics between a trawl with a grid section and the same trawl without a grid section. A video camera was used to observe fish escape in the grid section. The results indicate that the grid system reduced the flounder catch rate (mainly winter flounder, Pseudopleuronectes americanus) by 51.3%, and skates (mainly winter skate, Leucoraja ocellata and little skate, Leucoraja erinacea) by 29.4%, while there were no differences in the catch of Atlantic cod (Gadus morhua). While haddock was reduced by 37% by weight, the reduction was primarily small undersized individuals. There was no reduction in large haddock greater than 50 cm. Video observations indicates that flounders and cod mainly escaped from the bottom half of the grid while haddock were from the top half. These finding suggest that this system reduced low quota flounders, as well as discarded skates and small haddock, while retaining Atlantic cod and large size haddock. Underwater observations indicate that differential spacing (narrower on the top and wider on the bottom) may improve the system performance by releasing more flat-bodied fish, that were observed to escape from the bottom part of the grid, while retaining more haddock, which typically escape from the top part of the grid.

Adaptive design of a universal automotive ball joint separating device

Ball joint provides universal pivoting movement between the wheel hubs and control arms. The use of conventional ball joint separators was marred by cracks, damage to the castle nut on the joint stud and inferior mechanical advantage. An adaptive design was therefore necessary in response to these performance deficits and reiterated failures. The objective of this study was to offer the design and production of a universal ball joint separating device. GRANTA Selector was utilised in new material search. Design process was realized through ANSYS finite element analysis and structural stress analysis was performed using a load range of 200–1400 N. Optimal conditions of effort arm (mm) = 67.50, load arm (mm) = 66.38 and pitch (mm) = 2.50 were obtained at Mechanical Advantage (MA) of 0.85 giving an overall device efficiency of 83.51%. The maximum stress and maximum deformation respectively occurred close to the pivot at the base of the bottom half and at the tip of the top part of the ball joint separator. So, it was concluded that the effects of the control variables and their optimization were regarded as very useful to ascertain the optimum mechanical advantage of the device. The stress however is less than the yield strength of high carbon steel selected for device production and the separator performed the required tasks without failure.

The rise of US earnings inequality: Does the cycle drive the trend?

We document that declining hours worked are the primary driver of widening inequality in the bottom half of the male labor earnings distribution in the United States over the past 52 years. This decline in hours is heavily concentrated in recessions: hours and earnings at the bottom fall sharply in recessions and do not fully recover in subsequent expansions. Motivated by this evidence, we build a structural model to explore the possibility that recessions cause persistent increases in inequality; that is, that the cycle drives the trend. The model features skill-biased technical change, which implies a trend decline in low-skill wages relative to the value of non-market activities. With this adverse trend in the background, recessions imply a potential double-whammy for low skilled men. This group is disproportionately likely to experience unemployment, which further reduces skills and potential earnings via a scarring effect. As unemployed low skilled men give up job search, recessions generate surges in non-participation. Because non-participation is highly persistent, earnings inequality remains elevated long after the recession ends.

Near-zone transmission caustic of a hanging water drop.

A water drop hanging from a house siding board after a rain shower is near-normally illuminated by sunlight either shortly after sunrise or before sunset. A focusing caustic consisting of a bright V-shape or U-shape with a small bright elliptical shape immediately above it is frequently seen on the next lower siding board. In addition, there are two broad regions of illumination immediately above the caustic, fanning out to the upper left and upper right. This complicated pattern, composed of a bright V-shape or U-shape, and the bottom half of the small bright elliptical-shape immediately above it, is caused by the hyperbolic umbilic diffraction caustic near the condition of maximum focus. This can be observed because, by a stroke of good fortune, the distance between the lower edge of a siding board and the flat portion of the next siding board beneath it is nearly equal to the paraxial focal distance of the caustic. Blocking off the light incident on the top, bottom, left side, and right side of the drop was used to determine the portion of the drop responsible for different parts of the caustic. The results were found to match the predictions for the hyperbolic umbilic caustic.

Investigation on the flow characteristics of a novel multi‐blade combined agitator by time‐resolved particle image velocimetry and large eddy simulation

AbstractWe investigated the flow characteristics in a tank of H/T = 1.5 stirred by a novel multi‐blade combined agitator (MBC) by using time‐resolved particle image velocimetry and large eddy simulation approach. The predictions were assessed by Y+ values, Taylor microscale and power spectrum analysis, as well as experimental validation of velocity distributions. Results demonstrate that the MBC agitator can load the energy into the system effectively with a power number of 12.5 in a turbulent regime, resulting in improved axial and radial mass exchange. The upper and lower short blades produce an axial down‐flow in the top half and an axial up‐flow in the bottom half, respectively. Part of axial flows change to radial flows by the radial pumping of the long blades, meanwhile, the impingement of two axial flows improves the axial mass exchange. These flow characteristics lead to an obvious improvement in the turbulent kinetic energy distribution uniformity with higher turbulent intensity.

Evaluation and comparison of gas production potential of the typical four gas hydrate deposits in Shenhu area, South China sea

The field production test of gas hydrate conducted in South China Sea has been proven to be successful, but the production still cannot satisfy the requirement for commercial production. In order to achieve a higher production efficiency, the numerical simulation code Tough + Hydrate was employed to estimate the detailed production potential of four typical coring sites XX01∼XX04 in Shenhu area, which have distinct reservoir conditions and are considered as the focus for production tests. Our simulation results show that the hydrate deposit at Site XX03 featured with the highest permeability has the most promising gas production, despite the least thickness 11.56 m of the hydrate-bearing layer. In addition, we have also investigated the impact of the controllable engineering facts on the production, which suggests that the lower depressurization pressure and longer perforated interval would contribute to a higher gas production. And when the lower water production is considered, the bottom half perforated interval would be a relatively more promising design for the production. This research gives a forward sight for production prediction and our findings may provide a theoretical guideline in selection and design of the production targets.

Active dipolar spheroids in shear flow and transverse field: Population splitting, cross-stream migration, and orientational pinning.

We study the steady-state behavior of active, dipolar, Brownian spheroids in a planar channel subjected to an imposed Couette flow and an external transverse field, applied in the "downward" normal-to-flow direction. The field-induced torque on active spheroids (swimmers) is taken to be of magnetic form by assuming that they have a permanent magnetic dipole moment, pointing along their self-propulsion (swim) direction. Using a continuum approach, we show that a host of behaviors emerges over the parameter space spanned by the particle aspect ratio, self-propulsion and shear/field strengths, and the channel width. The cross-stream migration of the model swimmers is shown to involve a regime of linear response (quantified by a linear-response factor) in weak fields. For prolate swimmers, the weak-field behavior crosses over to a regime of full swimmer migration to the bottom half of the channel in strong fields. For oblate swimmers, a counterintuitive regime of reverse migration arises in intermediate fields, where a macroscopic fraction of swimmers reorient and swim to the top channel half at an acute "upward" angle relative to the field axis. The diverse behaviors reported here are analyzed based on the shear-induced population splitting (bimodality) of the swim orientation, giving two distinct, oppositely polarized, swimmer subpopulations (albeit very differently for prolate/oblate swimmers) in each channel half. In strong fields, swimmers of both types exhibit net upstream currents relative to the laboratory frame. The onsets of full migration and net upstream current depend on the aspect ratio, enabling efficient particle separation strategies in microfluidic setups.

Root Responses of Five Japanese Afforestation Species to Waterlogging

The increase of waterlogged environments is of recent concern due to changes in precipitation regimes and the frequent occurrence of extreme rainfall events. Therefore, it is necessary to comprehend the effects and responses of waterlogging for a better understanding of forests and urban afforestation under changing environments. We investigated root responses of five Japanese afforestation species (Pinus thunbergii, Acer mono, Quercus serrata, Alnus hirsuta and Fraxinus mandshurica) to waterlogging. Potted seedlings grown under natural conditions were waterlogged at soil-surface level for 2.5 months during the growing season. The in-growth core method was used to distinctively measure root growth. As a result, fine root growth during the waterlogging period was significantly decreased for P. thunbergii, A. mono and Q. serrata. Furthermore, root tissue density (RTD) of pre-existing roots was decreased, which suggests root damage such as partial root death and root decay. On the other hand, for A. hirsuta and F. mandshurica, fine root growth was not decreased under waterlogging. For A. hirsuta, although fine root growth continued at the top half, it was decreased at the bottom half. Root damage such as a decrease in RTD was observed for pre-existing roots. For F. mandshurica, root growth continued at the top and bottom half, and root damage of pre-existing roots was not observed at either the top or the bottom. From our results, it was suggested that P. thunbergii was most sensitive, followed by A. mono and Q. serrata. A. hirsuta and F. mandshurica were relatively tolerant; however, the most tolerant was F. mandshurica, as pre-existing roots were not damaged by waterlogging. Overall, root responses could be grouped into three groups: (1) P. thunbergii, A. mono, Q. serrata; (2) A. hirsuta; (3) F. mandshurica. The observed responses may reflect the species’ natural distributions.

Cytokine and Growth Factor Delivery from Implanted Platelet-Rich Fibrin Enhances Rabbit Achilles Tendon Healing.

Tendons are hypocellular and hypovascular tissues, and thus, their natural healing capacity is low. In this study, we sought to evaluate the efficacy of platelet-rich fibrin (PRF) to serve as a bioactive scaffold in promoting the healing of rabbit Achilles tendon injury. For in vitro study, the essence portion of PRF was determined through bioluminescent assay. Furthermore, we analyzed the time-sequential cytokines-release kinetics of PRF and evaluated their effects on tenocytes proliferation and tenogenic gene expressions. In animal study, the rabbit Achilles tendon defect was left untreated or implanted with normal/heat-denatured PRF scaffolds. Six weeks postoperatively, the specimens were evaluated through sonographic imaging and histological analysis. The results revealed significantly more activated platelets on bottom half of the PRF scaffold. Cytokine concentrations released from PRF could be detected from the first hour to six days. For the in vitro study, PRF enhanced cell viability and collagen I, collagen III, tenomodulin, and tenascin gene expression compared to the standard culture medium. For in vivo study, sonographic images revealed significantly better tendon healing in the PRF group in terms of tissue echogenicity and homogeneity. The histological analysis showed that the healing tissues in the PRF group had more organized collagen fiber, less vascularity, and minimal cartilage formation. In conclusion, bioactive PRF promotes in vitro tenocytes viability and tenogenic phenotypic differentiation. Administration of a PRF scaffold at the tendon defect promotes tissue healing as evidenced by imaging and histological outcomes.

Insight into the Effect of the Continuous Testing and Aging on the so2 Sensing Characteristics of a YSZ (Yttria-stabilized Zirconia)-Based Sensor Utilizing ZnGa2O4 and Pt Electrodes

Insight into the Effect of the Continuous Testing and Aging on the so2 Sensing Characteristics of a YSZ (Yttria-stabilized Zirconia)-Based Sensor Utilizing ZnGa2O4 and Pt Electrodes

Surface related degradation phenomena in P-type multi-crystalline silicon at elevated temperature and illumination

As a non-negligible part of light and elevated temperature induced degradation (LeTID), the studies of surface related degradation are rare, and the complex mechanism hinders the research in this field. In this paper, the degradation behaviors of passivation quality on the surface of P-type multi-crystalline silicon were mainly analyzed during LeTID. Results shown that effective minority carrier lifetime of passivated mc-Si wafers decreased in the range of 20–50% after it got to the full degraded during light soaking at 80 °C. The fixed charges at the interface between passivation layer and silicon bulk increased slightly after full degradation, which had little effect on field-effect passivation. Long-term illumination resulted in a certain increase in interface states density (Dit) in the bottom half of bandgap. According to the result that the increment of Dit of ungettered samples was higher than that of phosphorus diffusion gettered samples, it implied that the increase of interface defects might be caused by the diffuse of impurities in the bulk to the surface during the process of LeTID.

Personal Statements in General Surgery: An Unrecognized Role in the Ranking Process

Personal statements are a requirement of general surgery residency applications. Yet, their role in an applicant's final rank within a program remains unclear. This study explores the language used in personal statements to differentiate applicants in the general surgery residency ranking process. A textual analysis of general surgery residency applicant personal statements was performed. Using inductive coding and grounded theory, 3 main themes from personal statements were identified: my story, my future, my goals. These themes were utilized to build a dictionary consisting of over 400 descriptive terms in multiple categories. Data was extracted using the Linguistics Inquiry and Word Count program, which can linguistically determine basic characteristics from text. The data was stratified according to final rank and gender for analysis, using correlation and descriptive statistics. Large, urban, academic general surgery residency program. One hundred nineteen personal statements during the 2018 to 2019 application cycle were analyzed. All applicants were interviewed and considered for inclusion on our final rank list. There were 68 (57%) females on the final rank list with no difference in the distribution of gender between those in the top and bottom halves (p = 0.11). Overall, personal statements for the top applicants scored higher in grit than those in the bottom half (median 0.42% vs 0.35%, p = 0.03). Males ranked in the top half had less use of agentic (p = 0.04) and efficient/organized (p = 0.03) words when compared with males ranked in the bottom half. In contrast, females ranked in the top half used more grit words compared to those in the bottom half (median 0.45% vs 0.35%, p = 0.004). Linguistic differences existed in the personal statements of top- and bottom-ranked applicants to a general surgery residency program. These findings provide an adjunctive tool for differentiating applicants based on this underutilized component of the ranking process.

Cardiac Gene Expression and Histology in a Rat Model of Fat Embolism

IntroductionFat Embolism consequent to Triolein (T) intravenous injection in rats induces severe histopathologic pulmonary damage at 48 hours mostly related to vasculitis, peribronchial and septal inflammation with an increase in mast cells, and eventually, organ fibrosis. We previously reported that the hearts of the same animals at 48 hours did not show vasculitis of coronary arteries branches, inflammation or an increase in mast cells. The objective of this study was to determine if T treatment by 10 weeks induced changes in cardiac gene expression or histopathology related to fat embolism.Materials and Methods24 Sprague Dawley Rats (250–330g) were divided into two groups, 48 hour treatment and 10 week treatment (N=12 each). Six rats of each group were intravenously injected with 0.2 ml of T, and the other 6, 0.2 ml of normal saline. The rats were euthanized under general anesthesia 48 hours or 10 weeks after injection. A cut was made in hearts along the transverse plane; the top half of hearts were snap frozen in liquid nitrogen for gene expression studies and the bottom half was fixed in formaldehyde for histopathological evaluation similar to lung preparations. After RNA isolation, real time RT‐PCR was performed on genes associated with pathological cardiac hypertrophy or fibrosis (beta myosin heavy chain, alpha myosin heavy chain, skeletal muscle alpha actin, atrial natriuretic peptide, brain natriuretic peptide, vimentin, and collagen 1a1).ResultsDespite significant damage to the lungs, there was no significant changes in expression of any of these genes in the hearts of the rats treated with T, versus those of the saline treated group, whether sacrificed at 48 hours or 10 weeks post injection (P>0.05 ANOVA). Histopathological evaluation of the hearts at 10 weeks also did not show any damage in the myocardium in sections stained by H and E and no vasculitis, mast cell increase, or ventricular enlargements. Trichrome staining did not show any fibrotic increase in hearts of T injected animals, thus confirming the previous observations and gene expression analysis.ConclusionThere was a marked contrast in organ damage between hearts and lungs in this study in rats with T treatment. Hearts demonstrated no significant change in gene expression or histology demonstrating a lack of fibroblast infiltration, hypertrophy, or remodeling due to T treatment. Kidney, liver, brains, and aortas also showed varying degrees of histopathological damage compared to the severity of the damage of the lungs. The renin angiotensin system plays a key role in the pathogenesis of the lung damage with fat embolism and this system needs to be further explored for organ differences to fat embolism induced by T treatment.Support or Funding InformationSupported by the Catherine T. Geldmacher Foundation, St. Louis, MO

Relationship of Essential Oil Exposure to Anxiety in Zebrafish

This study focused on the relationship between differing essential oils and their impact on zebrafish anxiety. Five test groups were used to observe the behavioral responses and measure the quantitative cortisol levels of the fish after being exposed to three different essential oils, a carrier oil, and a control group (no oil). Two separate tests were designed to study 20 zebrafish over the course of 7 weeks. First, the swimming behaviors of the fish were observed using a basic novel tank test (NTT). The swimming patterns of the fish were recorded and the percent time that each fish swam in the top half of the tank was compared to the time each fish swam in the bottom half of the tank. Second, the zebrafish blood cortisol concentrations were measured immediately following their exposure to the differing test treatments using a cortisol extraction ELISA kit. The two data sets supported a strong trend regarding essential oil types in relation to swimming patterns and cortisol concentrations. Both data sets agreed that the test groups exposed to lavender, coriander, and fractionated coconut oil exhibited less anxious swimming behavior and lower levels of cortisol, while the zebrafish exposed to lemongrass oil and only water showed increased anxious behavior and higher levels of cortisol. Both tests showed strong trends when analyzed with a one‐way ANOVA test. The novel tank test data set had a p‐value of 0.07 and the cortisol extraction test had a p‐value of 0.06. The results of this study show that many questions can still be asked and answered regarding essential oil effects on cortisol levels and stress responses in zebrafish.

Economic development and converging household carbon footprints in China

There are substantial differences in carbon footprints across households. This study applied an environmentally extended multiregional input–output approach to estimate household carbon footprints for 12 different income groups of China’s 30 regions. Subsequently, carbon footprint Gini coefficients were calculated to measure carbon inequality for households across provinces. We found that the top 5% of income earners were responsible for 17% of the national household carbon footprint in 2012, while the bottom half of income earners caused only 25%. Carbon inequality declined with economic growth in China across space and time in two ways: first, carbon footprints showed greater convergence in the wealthier coastal regions than in the poorer inland regions; second, China’s national carbon footprint Gini coefficients declined from 0.44 in 2007 to 0.37 in 2012. We argue that economic growth not only increases income levels but also contributes to an overall reduction in carbon inequality in China.

Computational Analysis of Rotor-Blown-Wing for Electric Rotorcraft Applications

This Paper examines the performance of a rotor-blown-wing in hover and forward flight conditions. Flow solutions were generated using Helios, with a delayed detached eddy simulation model. The configuration is based on one set of rotors/wing of a quadrotor biplane tail-sitter aircraft. Simulations were conducted to assess the effect of varying angle of attack, rotor revolutions per minute with rotor speed, and rotor diameter. Two configurations were examined, the rotor-blown-wing baseline with two 60.96 cm diameter rotors and the configuration with four 30.48 cm diameter rotors. The smaller rotors were analyzed at the revolutions per minute corresponding to producing half the thrust of the rotor-blown-wing baseline rotor. The presence of the wing in hover resulted in the rotor-blown-wing baseline rotor operating at 1.9% lower power loading than the same rotor in isolation. In comparison, the configuration reduced power loading by 13.6% compared to the isolated rotor. In forward flight (airplane mode), an increasing angle of attack was shown to increase thrust produced on the downstroke side of the rotor. Furthermore, the presence of the wing increases the thrust produced on the bottom half of the disk. Both the blown wings increase the ratio from 3.2 for the isolated wing to 3.6 and 4.3 for the rotor-blown-wing baseline and configurations, respectively.

Spatiotemporal Seismotectonic Implications for the Izu–Bonin–Mariana Subduction Zone from b-Values

AbstractStudies on the physical properties of the entire Izu–Bonin–Mariana (IBM) subduction zone contribute to comprehensive seismotectonic understanding and earthquake potential assessment, especially given previous controversial conclusions. Determining seismic b-value is a method that has been used for other regions and is adopted here to study the spatiotemporal variations along the IBM system. Based on the frequency–magnitude distribution relation log10(N)=a−bM, b-values are mapped within the subduction zone using earthquakes with Mw≥2 after 2005. The b-value anomalies in cross sections indicate detailed seismotectonic characteristics against the regional geological background. The common characteristics from north to south: (1) regional high b-values at shallow depths in the overriding are associated with relatively low temperatures in thermal model, the bottom half of which correspond with highly serpentinized mantle wedge; and (2) low b-values at intermediate depths are associated with high temperatures along the primarily heated hydrated slab. In the Izu–Bonin segment, low b-values around the slab deflection at deep depths respond to stress buildup and shearing instability of metastable olivine in primarily heated hydrated slabs. In the Mariana segment, high b-values beneath the volcanic region at depths from the surface to 50 km and between 50 and 100 km are associated with extension and volcanism and the melting region, respectively. Temporal b-value variations indicate regional changes before and after large events for further seismic risk analysis. Stress drops of large intermediate and deep earthquakes are negligible to local stress state in strong flexure of the incoming slab. The rupture zone around the Pagan region at an approximate depth of 200 km and the region around the rifting–spreading transition in the northern Mariana trough at depths between 180 and 350 km are areas for potential large earthquakes.

The Critical Role of AlInP Window Design in III–V Rear-Emitter Solar Cells

This article highlights the critical role of window design on short circuit carrier collection in rear-emitter solar cells, as demonstrated through modeling and experiment using metamorphic GaAs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-y</sub> . Ultimately, if the window design is not carefully considered, surface depletion caused by Fermi level pinning at the window/air interface can extend into regions of active collection resulting in a large increase in effective window/base interface recombination velocity. This was experimentally shown here to result in a potential AM1.5G photocurrent loss of 8.1 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , or nearly 50%, based on integrated internal quantum efficiency (IQE). Associated IQE modeling and curve fitting indicate that the effective IRV at the GaAs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.75</sub> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.25</sub> /Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.64</sub> In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.36</sub> P interface is increased by multiple orders of magnitude when the window is not sufficiently thick or doped to fully contain the surface depletion to within the window layer. Calculations of the surface depletion depth as a function of doping and the surface Fermi pinning energy level provides insight into the fundamental limits of window thickness. This allows the estimation of the Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.64</sub> In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.36</sub> P surface pinning level to be at least 1.25 eV below the conduction band edge, or in the bottom half of the bandgap.