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Pulsatile insulin secretion by pancreatic beta cells is necessary for tight glucose control in the body. Glycolytic oscillations have been proposed as the mechanism for generating the electrical oscillations underlying pulsatile insulin secretion. The glycolytic enzyme 6-phosphofructokinase-1 (PFK) synthesizes fructose-1,6-bisphosphate (FBP) from fructose-6-phosphate. It has been proposed that the slow electrical and Ca(2+) oscillations (periods of 3–5 min) observed in islets result from allosteric feedback activation of PFKM by FBP. Pancreatic beta cells express three PFK isozymes: PFKL, PFKM, and PFKP. A prior study of mice that were engineered to lack PFKM using a gene-trap strategy to delete Pfkm produced a mosaic reduction in global Pfkm expression, but the islets isolated from the mice still exhibited slow Ca(2+) oscillations. However, these islets still expressed residual PFKM protein. Thus, to more fully test the hypothesis that beta cell PFKM is responsible for slow islet oscillations, we made a beta-cell-specific knockout mouse that completely lacked PFKM. While PFKM deletion resulted in subtle metabolic changes in vivo, islets that were isolated from these mice continued to exhibit slow oscillations in electrical activity, beta cell Ca(2+) concentrations, and glycolysis, as measured using PKAR, an FBP reporter/biosensor. Furthermore, simulations obtained with a mathematical model of beta cell activity shows that slow oscillations can persist despite PFKM loss provided that one of the other PFK isoforms, such as PFKP, is present, even if its level of expression is unchanged. Thus, while we believe that PFKM may be the main regulator of slow oscillations in wild-type islets, PFKP can provide functional redundancy. Our model also suggests that PFKM likely dominates, in vivo, because it outcompetes PFKP with its higher FBP affinity and lower ATP affinity. We thus propose that isoform redundancy may rescue key physiological processes of the beta cell in the absence of certain critical genes.

Tin plating at neutral and near-neutral pH is the preferable process in the application of electronic components such as capacitors and resistors, where the chemically sensitive ceramic and glass portions can be damaged by highly acidic solutions (often used in semiconductor packaging processes). Stannous ions are not as stable at elevated pH due to oxidation and hydrolysis, and plating demands the use of a large number of additives making the process control very challenging. Various analytical techniques are developed for automatic and comprehensive characterization of all inorganic and organic bath components including simultaneous detection of conductive salt, anti-whisker and chelator by near-infrared (NIR) spectroscopy, brightener by potentiometric titration, stannous ions by electrochemical method, and the breakdown stannic ions by spectro-titration.

We present a case report of a right atrial myxoma first diagnosed on a transthoracic echocardiogram after telephone consultations held in lieu of face-to-face consultations during the first wave of the COVID-19 pandemic. The echocardiogram was requested on the second telephone consultation 3 months after an initial presentation with a dry cough and fatigue due to new symptoms of palpitations and shortness of breath raising suspicion of heart failure. Virtual consultations continue to replace face-to-face consultations to avoid unnecessary exposure to COVID and reduce health care costs. This case report focuses on the importance of obtaining a systematic history, identifying red flags, referring to appropriate specialties and requesting the right investigations for early diagnosis and management of conditions with serious complications.

Recognizing the great potential of civil society organizations (CSOs) as drivers of social change, this study examines how CSOs’ work directed towards consumers—in this case, to make food consumption sustainable—could be analyzed and improved through insights in practice theory. This research scope adds to the sustainable consumption literature by shifting the lens from the rich body of scholarship examining the practices of households or organizations themselves to how CSOs can influence household practices. Interviews with five different Swedish CSOs serve as the study's main empirical basis. To analyze CSO activities that target households, we use practice theorist Alan Warde's well-established categorization of four integrative social practices of eating: (1) the supplying of food, (2) cooking, (3) the organization of meal occasions, and (4) aesthetic judgments of taste. Unlike some perspectives in sustainable consumption research that focus on consumer attitudes and behavioral change, a practice theory perspective encourages a view of consumption patterns as arising from complex and necessarily social configurations of human action formed in relation to evolving infrastructures and institutions in a cultural and historical context. In agreement with this, we suggest that the CSOs would generally benefit from focusing on particular practices, practice elements, and communities of practice. The different preconditions under which CSOs operate—such as material resource constraints and symbolic power resources—should further inform their chosen types of activities. However, we also conclude that the scale of the necessary societal changes ultimately requires increased integration and coordination of practical and political activities, not just among CSOs but throughout all spheres of society. Finally, we briefly outline avenues for further research. QC 20210113 Mistra Sustainable Consumption

Drive cycle pattern is different for different countries which depends on their traffic density, road condition and driver discipline. Drive cycle influences HEV`s components design, sizing and their ratings. Standard drive cycle data doesn't reveal much information to determine efficient and economic design of HEV`s components. In this research paper measurement and analysis of real time Indian road drive cycles (IRDC) are carried out for urban roads, state highway, national highway and express Highway where vehicles have their most run. Real time drive cycle data will expose impact of driver’s skills, traffic, road conditions and short acceleration / deceleration period, which can be represented on drive cycle chart. Analysis of IRDC in terms of rate of acceleration and deceleration, top speed, average speed with road length and analysed mathematically to find energy and power required for acceleration, normal operation and energy harvested during deceleration. Based on information from IRDC HEV`s components initial size are estimated. Initial estimated size is optimized to make HEV`s components design more efficient and economic. Teaching and learning based optimization algorithm (TLBO) and Multi objective genetic algorithm (MOGA) are used to optimize HEV`s components. Constraint of optimization algorithm are like engine and motor rating should be selected such that it has effective top speed with enough acceleration capability and can run enough distance to reach destination according to Indian urban, state, national and express highway pattern where cities are very closed compared with other countries and its regeneration component design should able to harvest maximum deceleration energy. For economic operation of HEV’s, running cost in terms of Rs. / Km. should be minimum.

Tetramethyl ammonium hydroxide (TMAH) has wide applications in semiconductor industry, including photoresist development, silica etching (especially Sigma etching), and wafer cleaning, etc. One of the critical areas of the photolithography process is the development of unexposed (negative) or exposed (positive) photoresists without pattern distortion. As a metal free, basic aqueous solution, TMAH is the most common positive photoresist developer providing no metal contaminations. The bath composition, especially the concentration of TMAH, is strictly controlled within the process specifications (~2.2 to 2.4 % (w/w)), since it greatly affects the developing rate and contrast [1]. Traditional monitoring of TMAH concentration does not suffice for the modern needs of a sub-20 nm IC fabrication process. Additional critical parameters include dissolved carbonate and proprietary surfactants.

background Night blood pressure (BP) predicts patient outcomes. Variables associated with night BP response to antihypertensive agents have not been fully evaluated in essential hypertension. methods We sought to measure night BP responses to hydrochlorothiazide (HCTZ), atenolol (ATEN), and combined therapy using ambulatory blood pressure (ABP) monitoring in 204 black and 281 white essential hypertensive patients. Initial therapy was randomized; HCTZ and ATEN once daily doses were doubled after 3 weeks and continued for 6 more weeks with the alternate medication added for combined therapy arms. ABP was measured at baseline and after completion of each drug. Night, day, and night/day BP ratio responses (treatment − baseline) were compared in race/sex subgroups. results Baseline night systolic BP and diastolic BP, and night/day ratios were greater in blacks than whites (P < 0.01, all comparisons). Night BP responses to ATEN were absent and night/day ratios increased significantly in blacks (P < 0.05). At the end of combined therapy, women, blacks, and those starting with HCTZ as opposed to ATEN had significantly greater night BP responses (P < 0.01). Variables that significantly associated with ATEN response differed from those that associated with HCTZ response and those that associated with night BP response differed from those that associated with day BP response. conclusions In summary, after completion of HCTZ and ATEN therapy, women, blacks, and those who started with HCTZ had greater night BP responses. Reduced night BP response and increased night/day BP ratios occured with ATEN in blacks. Given the prognostic significance of night BP, strategies for optimizing night BP antihypertensive therapy should be considered.

Humanity’s detrimental impacts on the Earth’s ecosystems have been studied extensively, and these impacts’ negative consequences across societal groups, nations, and generations, have garnered much attention, from the scientific community as well as from civil society, where the attention often has been directed at how unfair the distribution of these environmental burdens is. The fairness of the distribution of global environmental benefits, however, has seen much less study, especially when it comes to the implementation of such concerns for fairness in environmental policy. In support of the research project Beyond GDP-growth, this thesis has centered on a Swedish context, and has focused on the term “biocapacity”, which is a quantifiable measure of many environmental benefits, and in the thesis is defined as the ability of terrestrial ecosystems to regenerate the biological materials extracted by humans. The thesis has then aimed to determine the current potential for the implementation of a fair distribution of global biocapacity in Swedish environmental policy, mainly by way of a series of interviews with individuals engaged in different forms of Swedish environmental work – from different levels of government, to civil society and centers of scientific research. It is concluded that the current potential for the implementation of a fair distribution of global biocapacity in Swedish environmental policy is primarily hindered by the seeming lack of a relevant discourse on the matter. Without such a discourse, a lack of public understanding of the subject is deemed to cause poor public support for any potential policies promoting a fair distribution of global biocapacity. It is suggested that a relevant and effective discourse is best achieved through transparent trade practices, and by the active participation of scientific experts and other actors outside of the political system. Furthermore, the thesis discusses the usefulness of the term “biocapacity” in this context, concluding that more research is needed, while identifying the main point of contention as what the term is intuitively understood to mean, as well as whether or not it can be used as a means to achieve a focused public discourse on the fair distribution of environmental goods. Mänsklighetens skadliga inverkan på jordens ekosystem har studerats i stor utsträckning, och den här inverkans negativa konsekvenser för olika samhällsgrupper, länder och generationer har fått mycket uppmärksamhet från både forskningsvärlden och civilsamhället, där det främst har fokuserats på den orättvisa fördelningen av dessa ”miljöbördor”. Men, rättvisa när det kommer till fördelningen av ”miljönyttor” har studerats betydligt mindre, särskilt i samband med hur sådana rättviseaspekter kan implementeras i miljöpolicy. Den här uppsatsen har – i en svensk kontext och som stöd till forskningsprojektet Bortom BNP-tillväxt – fokuserat på en kvantifierbar term kallad ”biokapacitet”, som innefattar många miljönyttor, och i uppsatsen definieras som landbaserade ekosystems kapacitet att regenerera de biologiska material som människor extraherar. Uppsatsen har sedan ämnat att undersöka de nuvarande förutsättningarna för implementeringen av en rättvis fördelning av global biokapacitet i svensk miljöpolicy, främst genom en serie intervjuer med individer som i olika sammanhang är engagerade i svenskt miljöarbete – från kommunal till statlig nivå, samt i civilsamhället och i forskningssammanhang. Uppsatsen utmynnar i slutsatsen att de nuvarande förutsättningarna för implementeringen av en rättvis fördelning av global biokapacitet i svensk miljöpolicy främst begränsas av att den offentliga debatten till synes inte behandlar ämnet nämnvärt. Utan en offentlig debatt om ämnet förmodas den resulterande kunskapsbristen hos allmänheten leda till ett bristande offentligt stöd för policyförslag som förespråkar en rättvis fördelning av global biokapacitet. En relevant och effektiv offentlig debatt tros bäst kunna uppstå genom transparent handel och ett aktivt deltagande av experter från forskningsvärlden, samt andra utompolitiska aktörer. Dessutom diskuterar uppsatsen nyttan av begreppet ”biokapacitet” i en sådan debatt, och kommer fram till att vidare studier krävs för att nå en tillfredsställande slutsats. Uppsatsen identifierar dock den intuitiva uppfattningen av termens betydelse, samt frågan om termen kan användas för att uppnå en fokuserad debatt på ämnet, som de främsta problemområdena som behöver behandlas. Beyond GDP-growth (sv. Bortom BNP-tillväxt)

Recording physics, design considerations, and fabrication of bit-patterned magnetic medium for next generation data storage systems is presented. (Co/Pd)N magnetic multilayers are evaluated as candidates for bit-patterned medium recording layer materials for their high and easily tunable magnetic anisotropy. The optimized patterned multilayers used in this study had coercivities in excess of 12-14 kOe. Bit patterning was accomplished using ion-beam proximity printing, a high-throughput direct write lithography where a large array of ion beamlets shaped by a stencil mask is used to write an arbitrary device pattern. It is found that the nature of magnetization reversal strongly depends on bit edge imperfections and is likely to contribute to switching field distribution.

Recording physics, design considerations, fabrication, and characterization of bit-patterned magnetic medium for next generation data storage systems is presented. (Co/Pd) N magnetic multilayers are evaluated as candidates for bit-patterned medium recording layer materials for their high and easily tunable magnetic anisotropy. Optimized patterned multilayers used in this study had coercivities in excess of 12-14 kOe. Bit patterning was accomplished using ion-beam proximity printing, a high-throughput direct write lithography where a large array of ion beamlets shaped by a stencil mask is used to write an arbitrary device pattern. It is found that the nature of magnetization reversal strongly depends on bit edge imperfections and is likely to contribute to switching field distribution.

An approach to fabrication of a patterned magnetic recording medium for next generation data storage systems is presented. (Co/Pd)n magnetic multilayers are evaluated as candidates for patterned medium materials for their high and easily controllable magnetic anisotropy. The multilayer films deposited on a Ta seed layer enable high intergranular exchange coupling—an essential feature of a patterned magnetic recording medium. The quality of (Co/Pd)n superlattices was optimized via deposition conditions and monitored using low-angle x-ray diffraction. An estimated in-plane (hard-axis) magnetization saturation field in excess of 40 000 Oe was observed. Vertical (easy-axis) hysteresis loops for as-deposited continuous magnetic multilayers exhibited a low coercivity of 930 Oe, indicating highly uniform (magnetically) films with weak domain wall pinning. Ion-beam proximity lithography was used to pattern magnetic multilayers into 43 nm islands on a 135 nm pitch. Following patterning, easy-axis coercivity increased nearly 15-fold to 12.7 kOe.

Wireless Sensor Networks are often deployed in unattended and hostile environments. These networks are susceptible to harsh physical conditions and attacks from adversaries. Sensor nodes have limited power, memory and computational ability and thus are vulnerable to capture. A few malicious adversaries can easily compromise sensor devices and inject false data to disrupt the integrity of the network. In this paper, we address this problem by proposing a three tiered architecture established upon a trust based framework which distinguishes illegal nodes from legal ones and filters out deceitful and forged data. Simulation results demonstrate that our trust based framework is an efficient approach to identify the trustworthiness of data.

We assessed adverse metabolic effects of atenolol and hydrochlorothiazide among hypertensive patients with and without abdominal obesity using data from a randomized, open-label study of hypertensive patients without evidence of cardiovascular disease or diabetes mellitus. Intervention included randomization to 25 mg of hydrochlorothiazide or 100 mg of atenolol monotherapy followed by their combination. Fasting glucose, insulin, triglycerides, high-density lipoprotein cholesterol, and uric acid levels were measured at baseline and after monotherapy and combination therapy. Outcomes included new occurrence of and predictors for new cases of glucose ≥100 mg/dL (impaired fasting glucose), triglyceride ≥150 mg/dL, high-density lipoprotein ≤40 mg/dL for men or ≤50 mg/dL for women, or new-onset diabetes mellitus according to the presence or absence of abdominal obesity. Abdominal obesity was present in 167 (58%) of 395 patients. Regardless of strategy, in those with abdominal obesity, 20% had impaired fasting glucose at baseline compared with 40% at the end of study ( P P

We describe the fabrication of large-area magnetic ring structures using ion beam proximity lithography (IBPL) to pattern an array of circular openings and then use a conforming oxide coating to define the ring structure through the sidewall coating. Arrays of Permalloy rings with sub 500 nm outer diameter and 150 nm inner diameter on a 650 nm pitch over a 5.5 mm times 6 mm area were fabricated to study transitions between the micromagnetic configurations within these structures. The results suggest that the field required for onion-to-vortex transition and field required for vortex-to-onion transition to be 0Oe and 400Oe, respectively.

We describe a self-limiting, low-energy argon-ion-milling process that enables noncircular device patterns, such as squares or hexagons, to be formed using precursor arrays of uniform circular openings in poly(methyl methacrylate) defined using electron beam lithography. The proposed patterning technique is of particular interest for bit-patterned magnetic recording medium fabrication, where square magnetic bits result in improved recording system performance. Bit-patterned magnetic medium is among the primary candidates for the next generation magnetic recording technologies and is expected to extend the areal bit density limits far beyond 1 Tbit/in 2 . The proposed patterning technology can be applied either for direct medium prototyping or for manufacturing of nanoimprint lithography templates or ion beam lithography stencil masks that can be utilized in mass production.

We describe the lithographic structuring of large-area patterned medium samples with sub-50 nm features using ion beam proximity lithography (IBPL). The quality of the patterns formed in IBPL system is primarily limited by the quality of the stencil masks. Hence, the emphasis of this work has been to develop a reliable mask fabrication process that can achieve a size uniformity that is suitable for patterned media. We have developed a mask fabrication approach that incorporates palladium as a hard mask for transferring the lithography pattern through a silicon nitride membrane. A conformal gold coating allows for further reduction of the mask features without a significant increase in the feature size variation. An average standard deviation of 3 nm and 5 nm was measured during various steps of the stencil mask fabrication and after printing using IBPL in PMMA resist, respectively. Patterned medium prototypes with features ranging from 40 nm to 300 nm have been fabricated and magnetic properties measured. A 6-12 fold increase in coercivity was measured for multilayer samples after patterning. Ion irradiation of patterned multilayer samples was also studied as a means to control magnetic anisotropy as well as to evaluate possible ion irradiation damage involved in ion-beam proximity lithography patterning. Patterned multilayer samples show a decrease in coercivity from 11 kOe for as-patterned to 0.3 kOe for 800 muC/cm2 and suggests that ion irradiation can be an integral part of bit patterned medium fabrication for anisotropy control.

Design considerations and fabrication of bit-patterned magnetic recording media are presented. The application of ion-beam proximity printing, a high-throughput direct-write lithography, to media patterning is evaluated. Ultra-high magnetic anisotropy (Co/Pd)N magnetic multilayers are analyzed as candidates for patterned recording layers. Following patterning, optimized multilayers are shown to exhibit coercivity values well in excess of 14kOe. It is found that the magnetization reversal in patterned bits takes place via domain wall nucleation and propagation. The nucleation field and the location of the nucleation site strongly depend on the bit edge imperfections and contribute to finite switching field distribution. Playback off a bit-patterned media using various magnetic reader designs is analyzed using reciprocity theory.

We present the results of micromagnetic studies on realistic patterning defects in perpendicularly oriented magnetic thin films. Both undercut and line edge roughness are investigated systematically with simulations using simple test structures to see the effect of the side wall angle, the roughness amplitude on a nanostructureiquests switching field, and the roughness period on mathematically tractable figures. We then run simulations of hysteresis loops of actual 200 nm diameter nanostructures using AFM images to define the structure boundary and compare the results to MFM images of DC demagnetized dots.

Nickel deposit is valued for its barrier properties and is used to separate other deposition layers (i.e.Cu/Sn and Sn Alloys; Cu/Pd; Cu/Au) which would otherwise form intermetallics. It is widely employed in the semiconductor industry for different packaging schemes, e.g. under bump metallization, base layer under noble material for TSV wafer-level packaging. [1]. Semiconductor device must be able to survive extreme temperature swings during multiple cycles of operation. This favors the use of a nickel sulfamate formulation, known for its low deposit stress. The inherently low current efficiency of Ni electrodeposition leads to pitting due to hydrogen bubbles. Tools with horizontal wafer orientation can usually spin off bubbles by fast wafer rotation. Tools with vertical wafer orientation typically require the use of organic surfactants to reduce surface tension and promote the release of bubbles from the surface. Surfactant is removed from the process by drag-out and foaming which requires tight control. Not enough surfactant increases the potential for pitting, while too much can cause inclusion of organics into the deposit which can result in defects and reliability failures by a burn out during heat cycling [2]. One process control option is to measure surface tension. However, this property by itself is not highly selective. The same concentration of surfactant can cause different surface tensions depending on the concentrations of other components. Authors has developed a highly selective and accurate potentiometric titration method to address this process demand. Details of the method will be elaborated in the presentation. Type I Brighteners are typically used for nickel electro-deposition to fine-tune the stress level by incorporating sulfur-bearing compounds into the deposit. The process window for these chemicals is narrower than for surfactants with the potential for out-of- spec related to stress level, deposit purity, and reliability under heat cycling. Traditional metrology for brighteners employs long and hazardous methods such as polarography and HPLC.. A non-reagent, real-time, spectral analytical method was developed by ECI for this application. Sulfamate ion is known to decompose at the anode producing azodisulfonate which itself behaves as a “Type I Brightener” [3]. However, the generation of this compound depends on the type of anodes and whether a membrane is used to separate anode and cathode compartments. Figure 1 shows spectra of the same process solution after operation in different process tools. Acceptable deposition was obtained only in the process tool where azodisulfonate products were detected in the solution. It can be argued that use of these products as an additive is better than lengthy burn-ins to generate these products. The truly unique challenge of nickel deposition for semiconductor packaging is related to the presence of a lithographic photoresist mask on the surface. Ideal positive type photoresist should be fully resistant to solutions in unexposed form but quickly dissolves in developer following UV exposure. In reality, unexposed photoresist is slowly attacked by the hot nickel solution. The presence of photoresist has detrimental effects on the performance of Ni baths. The concentration of leached photoresist is a main limiting factor for electrolyte lifetime. Thus, its metrology becomes crucial to bath dump and/or bleed and feed adjustment. A non-reagent spectroscopy method has been developed by ECI to monitor the accumulation of photoresist (Figure 2). The presentation will show some examples of this method. In conclusion, a comprehensive array of metrology techniques was developed to monitor surfactant, stress controlling compound, and leached photoresist in the nickel electrodeposition processes used in the semiconductor industry. References: M.Paunovic, P.J.Bailey, R.G. Schad, D.A. Smith J.Electrochem.Soc, 141 (7), 1843 (1994). L.M.Wang. J.Electrochem.Soc, 156 (6), D204 (2009) O.J. Klingenmaier, Plating, 52, 1138 (1965)

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In this work, the physics of magnetization reversal in patterned high anisotropy (Co∕Pd)n magnetic multilayer arrays is investigated where the magnetic island size, pitch, recording layer thickness, and the underlying multilayer magnetic properties are varied. Magnetization reversal was studied using magneto-optical Kerr effect magnetometry and magnetic force microscopy and supported by micromagnetic modeling. It is found that magnetic island dimension and/or pitch cannot alone explain the variations in the switching behavior of the patterned arrays and the observed values of switching field distribution (SFD). It is found that the ratio of switched magnetic islands to the total number of islands for a giving reversing field depends strongly on the magnetic island geometry. Stray fields from neighboring magnetic islands result in relatively minor influence on the switching characteristics. Micromagnetic modeling was used to further understand the magnetization reversal in patterned arrays. It is found tha...

We have identified an important microstructural origin of the switching field distribution (SFD) in patterned Co∕Pd multilayer nanodots. In this study, we patterned a marked array of 115nm Co∕Pd nanodots on 50-nm-thick Si3N4 substrate. We identified the dots with unusually small and large (>2 standard deviations of the mean) switching fields with magnetic force microscopy, followed by microstructural characterization of the same dots with transmission electron microscopy (TEM). From electron diffraction, we found that most nanodots with small switching fields have strong (200) spots, whereas those with large switching fields lack these spots. While bright-field TEM images reveal an average grain size of 7nm, dark-field images of the (200) spots reveal on average, a single grain of >10nm in lateral dimensions. Since we observed a direct correlation between strong (200) reflections and small reversal fields, we conclude that the largest grain in each nanodot, with an in-plane [001] is the likely cause for p...

We present evidence that low temperature atmosphere annealing of Co∕Pd magnetic multilayers reduces both the dipolar and exchange interactions, but the dipolar interaction decreases very rapidly at the lowest temperatures. We also infer cobalt oxide formation at grain boundaries. This results in a reduction of the exchange between grains, reduces the length scale of ordering in the ac demagnetized state of the films. We demonstrate that this is the result of the decoupling the grains.

Ion irradiation of continuous and patterned (Co∕Pd)n magnetic multilayer films has been studied as a mean to control magnetic anisotropy as well as to evaluate possible ion irradiation damage involved in ion-beam proximity lithography patterning. The coercivity of patterned medium was found to decrease from 11kOe for as patterned samples to 0.3kOe for samples with 800μC∕cm2 ion irradiation. Remnant squareness of the patterned samples remained essentially unchanged. As the number of bilayers increases in the sample, the effects vary, suggesting that several mechanisms of damage occur. Significantly, for typical irradiation doses used in ion-beam proximity lithography, no measurable alteration of magnetic properties was observed.

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In ion beam proximity lithography, ions that are incident on the nominally opaque regions of a stencil mask can scatter into the open windows and escape, exposing a wide area of the substrate. Since these ions can lose much of their initial energy in the mask, the scattered particle exposure is concentrated near the resist surface. The resulting loss of contrast can be mitigated to some extent by using aperture array lithography (AAL) where a mask of reduced density minimizes the number of windows from which a scattered ion can escape. Even so, the problem worsens as the pitch of an array, printed by multiple, offset exposures of the AAL mask, shrinks below about 250nm. The only solution is to increase the mask thickness, hence the window aspect ratio, to reduce the escape angles of the scattered particles. In this article, the authors characterize an effective background dose η in the first 75nm of poly(methylmethacrylate) resist for 30keV He+ ion exposures of 0.6μm thick masks with 45, 80, and 110nm cir...