Self-limiting Process Research Articles

6601 A Case of Recurrent Painless Thyroiditis and Discussion of Management

Abstract Disclosure: M.C. Slack: None. S. Grock: None. Introduction: Painless (silent) thyroiditis is characterized as a subacute and generally self-limited disease process in which patients develop transient thyrotoxicosis, which is often followed by a hypothyroid phase before entering the recovery euthyroid phase. Given high frequency of positive thyroid antibodies, it may be autoimmune-mediated; recurrence is rare. Here we present a case of recurrent painless thyroiditis and discuss management options. Clinical Case: A Korean woman was followed by endocrinology from age 38 to 60 and experienced at least seven episodes of painless thyroiditis over this time. The episodes occurred without an identifiable trigger and were not preceded by viral illness. During episodes she developed palpitations, hair loss, and dyspnea on exertion and biochemical evidence of thyrotoxicosis with TSH suppressed to <0.2 mIU/mL (normal 0.3-4.7) and elevated free T4 levels as high as 5.4 ng/dL (normal 0.8-1.7). TSI, TPO, and TSH receptor antibodies were checked during multiple episodes and resulted negative, though thyroglobulin antibody was significantly elevated. A radioactive iodine uptake scan was obtained during an active episode of thyroiditis and revealed diffusely low uptake. The patient’s episodes lasted approximately two to three months before normalization of her TSH and FT4. She had at least one instance of transient hypothyroidism after thyrotoxicosis with a TSH of 13.2 and FT4 of 0.6 which subsequently normalized 6 weeks later. The patient did not have known cardiovascular disease and DXA scans revealed mild osteopenia with the lowest T-score -1.3. RAI was considered for the patient based on the total number and increasing frequency of her episodes. She ultimately declined treatment with RAI and continues to follow with endocrinology. Clinical Lessons: While the deleterious effects of prolonged hyperthyroidism (e.g. osteoporosis, arrhythmia, cardiovascular disease) are well known, it is unclear what risk recurrent painless thyroiditis episodes pose. As there are no guidelines regarding treatment, clinical gestalt incorporating frequency and duration of episodes, as well as symptoms, is often used to determine if definitive management is indicated. There are case reports in the literature of treatment of recurrent thyroiditis with RAI ablation performed during a euthyroid state, which eliminated recurrence of episodes but did lead to permanent hypothyroidism necessitating hormone replacement. Surgical thyroidectomy may also be considered in select patients. This case highlights the challenges in treating rare cases of recurrent painless thyroiditis given the lack of research or established guidelines. It is reasonable to consider the frequency, severity, and total number of episodes, as well as patient risk factors, symptoms, and preferences when making recommendations regarding management. Presentation: 6/1/2024

Nursing Interventions in Primary Care for the Management of Maladaptive Grief: A Scoping Review.

Grief is a natural and self-limited adaptation process to a new reality that emerges after a significant loss (whether real or perceived), with a broad variety of manifestations that exert an impact on a grieving person's health. The study aim was to synthesize the evidence available about the interventions carried out by Primary Health Care nurses, by means of an individual approach to reduce maladaptive grief or maladaptive grief risk. A scoping review was conducted (November and December 2023) through searches in Medline, Cinahl, Web of Science, ProQuest and Scopus using MeSH terms combined with Booleans. Primary research of any design in adult people undergoing grief situations and receiving professional assistance by nurses in the primary, home and community care contexts published after 2009 in English, Spanish or Portuguese languages were included. Excluded publications were those conducted in in-hospital clinical settings and which did not correspond to research designs or the gray literature. The screening process was carried out by two reviewers using the appropriate JBI critical appraisal tools for each design and discrepancies were resolved by a third reviewer. A total of n = 10 studies were included (n = 4 qualitative, n = 2 RCTs, n = 1 quasi-experimental, n = 2 cross-sectional observational, and n = 2 mixed methods). The qualitative studies identified topics and subtopics of professionals' and families' experiences of grief. The observational studies analyzed symptoms and factors associated with the grieving process. Interventions consisted of cognitive-behavioral therapies delivered by psychological specialists who assessed the severity of grief in a range of cultural contexts using different instruments. The evidence retrieved from the studies that address the reduction in maladaptive grief or maladaptive grief risk is not conclusive. There is a need to increase both the number and the methodological quality of studies assessing the effectiveness of Nursing care in Primary Health Care for individuals experiencing maladaptive grief or maladaptive grief risk. Further research should focus on experimental studies, developing specific interventions conducted by nurses to address individual's grief and prevent maladaptive grief.

Spectroscopic investigation of oxidation in GaSe 2D layered materials

GaSe, a two-dimensional layered metal monochalcogenide, has recently attracted growing interest due to its unique electronic properties and potential technological applications. In this study, we investigate the oxidation mechanisms and properties of GaSe exposed to air for different durations, with the intensive use of Raman spectroscopy, combined with atomic force microscopy (AFM), photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS). Raman analysis reveals the oxidation of GaSe, resulting in the formation of a thin layer comprising Ga2Se3, Ga2O3, and amorphous selenium. Utilizing these signatures, oxidation is then tracked. Raman spectroscopy reveals that GaSe layer becomes oxidized almost immediately after exposure to air. However, the oxidation is a self-limiting process, taking roughly 15 min to construct an 8 Å thick layer of Ga₂O₃. XPS analysis shows a good agreement with Raman analysis. The polarized Raman study suggests that the Ga₂Se₃ and Ga₂O₃ layers tend to reach an oriented structural state over time. In ambient conditions, the intensity of all Raman modes and the luminescence decreases, linked to reduction in GaSe thickness. By using various Raman excitation wavelengths, we highlight the depth-dependent oxidation dynamics in this 2D layered GaSe material.

Teething - filling in the gaps….

Dentists and dental care professionals may be faced with concerns from parents and carers regarding teething in infants and young children. Teething is a normal physiological and self-limiting process; however, the diverse signs and symptoms that have, over time, been attributed to teething, can make diagnosis challenging. Appropriate diagnosis is crucial in preventing the potentially life-threatening sequalae of dismissing symptoms as teething and delaying appropriate treatment of a systemically unwell child. Management of teething can be approached in a five-step process based on the National Institute for Health and Care Excellence clinical knowledge summary on teething. These include: 1) history-taking, clinical examination, diagnosis and referral of systemically unwell or severely distressed children for urgent medical review; 2) providing parental/carer reassurance, information and preventative advice; 3) simple, non-pharmacological management strategies; 4) pharmacological intervention; 5) safety-netting advice in case the child becomes systemically unwell, has prolonged symptoms, or is in severe distress. The purpose of this article is to bridge knowledge gaps regarding teething to enable appropriate diagnosis and encourage dissemination of preliminary information and ensure appropriate referral by frontline dental professionals.

Neuritis ossificans mimicking a malignancy in a child: case report and literature review.

We present the case of a child with neuritis ossificans after acute trauma, treated conservatively. The aim of the review is to compare several parameters in this disease. Emphasis is placed on the clinical-radiological features distinguishing neuritis ossificans from malignancy to avoid unnecessary biopsy and surgery.A literature review was performed. Only 18 cases were described. Except for one, all describe adults, and none had acute trauma. Nearly all were treated surgically.Our 13-year-old patient presented with posterior knee pain after trauma. MRI demonstrated a mass within the tibial nerve with oedema, some lymph nodes and increased avidity on 18fluoro-2-deoxyglucose-positron emission tomography. These findings can be reactive but also associated with malignancy. However, eggshell-like calcifications in the periphery of the mass were seen on CT. Biopsy and resection were proposed. Follow-up visits over the next weeks showed remarkable clinical improvement. Wait-and-scan was advised after international discussion. Follow-up imaging after 2months showed resolution of the oedema and volume reduction of the mass, suggesting a benign pathology. Diagnosis of neuritis ossificans was proposed based on the clinical and radiological features. There was a favorable course with no complaints after twomonths. Imaging after sevenmonths showed an almost complete regression.Neuritis ossificans should be considered within a painfull (mono)neuropathy. The initial inflammatory phase may mimic malignancy, misleading clinicians toward biopsy or surgery with the risk of nerve damage. As seen in our case, neuritis ossificans can be a self-limiting process. Therefore, conservative therapy should be considered with a wait-and-scan approach.

Immune recovery uveitis: an ocular manifestation in HIV/AIDS receiving treatment.

This article intends to briefly discuss AIDS, summarize the current literature on immune recovery uveitis, describe its ocular manifestations and complications, and tackle its complex management. The clinical picture of immune recovery uveitis is still evolving. Up to today, there are still no definite criteria for immune recovery uveitis, and although closely associated with cytomegalovirus retinitis and HIV/AIDS, there are several cases of similar intraocular response in non-HIV patients. The exact pathology for this paradoxical inflammatory reaction remains unclear; however, there is an interest in identifying biomarkers to determine underlying mechanisms and identify patients at risk. The management of this disease also remains a challenge and no standardized treatment approach exists currently. Immune recovery uveitis is an important cause of visual morbidity particularly in HIV/AIDS patients receiving highly active antiretroviral. It is a paradoxical reaction that is frequently associated with a prior cytomegalovirus retinitis infection. Although it can be a transient and self-limiting process, there is a complex decision on the timing of antiviral treatment and the initiation of antiretroviral treatment to prevent immune recovery uveitis. Furthermore, a substantial challenge arises in balancingtreatment decisions for complications in refractory cases.

Amiodarone-induced thyrotoxicosis type 2: the role of differential diagnosis in patient management

The antiarrhythmic drug amiodarone can affect the function of the thyroid gland, contributing to the development of thyrotoxicosis or hypothyroidism. The development of thyrotoxicosis exacerbates the cardiovascular pathology present in patients: it leads to the progression of left ventricular dysfunction, recurrence of rhythm disturbances, increasing the risk of adverse outcomes. Timely diagnosis of thyrotoxicosis in the treatment of amiodarone is of fundamental importance in choosing the right therapeutic tactics, which is determined by the type of amiodarone-induced thyrotoxicosis (AmIT), the state of the cardiovascular system, and the risk of recurrent arrhythmias. In type 1 AMIT, the main method of controlling the relief of thyrotoxicosis is thyroostatic therapy with the possibility of subsequent radical treatment (radioiodine therapy, thyroidectomy). Type 2 AmIT is a self-limiting process, however, for the treatment of patients with moderate to severe amiodarone-induced thyrotoxicosis type 2, glucocorticoids are the first-line drugs. With a mixed version of AmIT, a combination of antithyroid drugs and glucocorticoids is recommended. This review presents a clinical case of a patient with type 2 AmIT who was treated with thyrostatic drugs for a long time without achieving an effect.

A Case of Baker’s Cyst with Synovial Chondromatosis of Knee

Synovial chondromatosis is a benign condition which arises from synovial membrane or bursae around the joints. Joint abnormalities in the form of arthritic or mechanical conditions such as detachment of osseocartilaginous fragments from the articular surface are its secondary associations. Rarely there maybe involvement of the Baker’s cyst. Here we report a case in which a 60-year-old female came with complaints of pain, swelling and restriction of movement of right knee joint for the past one year. After careful clinical and radiological examination, it was diagnosed as Baker’s cyst complicated by synovial chondromatosis. After the diagnosis the patient underwent the following procedures: open synovectomy, cyst removal and thorough joint debridement. Synovial chondromatosis was confirmed histopathologically. Secondary synovial chondromatosis has features of osteoarthritic changes, lack of extensive synovial proliferation and complicated Baker's cyst which is not seen in primary synovial chondromatosis.
 Synovial chondromatosis (SC) is caused by metaplasia of the synovium into chondrocytes and is a rare benign disorder.[1,2] Primary synovial chondromatosis (PSC) is a self-limited process that occurs in an otherwise normal joint.[3] When synovial chondromatosis develops in a joint previously affected with disease, often posttraumatic or degenerative osteoarthritis, it is called as secondary synovial chondromatosis.[4] SC may involve any joint, but the most common joint involved is knee joint followed by hip joint, and small joints of the hand and wrist. Least involvement is seen in elbow and shoulder joint. [5] The disease is categorised into three phases according to Milligram classification: active intrasynovial disease without any loose bodies observed in the early phase, active disease and loose bodies observed in the transitional phase, and multiple loose bodies without any intrasynovial disease observed in the late phase.
 In orthopaedic practice, popliteal cysts are common occurrence; many of them are associated with degenerative or rheumatoid arthritis. The differential diagnoses become more complex when loose bodies and calcifications are noted within the joint on a radiograph. Here in, we are presenting a case of Baker’s cyst with synovial chondromatosis of knee treated by surgical excision and confirmed by histopathology.

Acute conjunctivitis – antibiotic susceptibility and resistance to different antibiotics in main Eye Hospital, Tripoli, Libya

Acute conjunctivitis is characterized by inflammation of the conjunctiva of less than 3 to 4 weeks duration, cellular infiltration, and exudation. It may also result in corneal, lid, or orbital involvement which may lead to various complications. Bacterial conjunctivitis is a self-limiting process, but topical antibiotic treatment is recommended to eradicate the pathogen and reduce symptom duration. A hospital-based prospective study was conducted in the emergency and casualty department in Zawyat Aldahmani Eye Hospital, Tripoli /Libya comprising out-patients (OPD) visiting the department from June to December 2019 (186 cases). The primary objective was to evaluate the bacteriological pattern and the secondary objectives were to evaluate seasonal variation and antibiotic sensitivity pattern of the isolates. Conjunctival swabs included patients from both sexes (males n_106 and females n_80) and different ages; 80.1% of adults of the whole studied cases and the rest were children under 12 years old. Staph. hominis (26.17%) was the predominant organism isolated throughout the study. The commonest single organism isolates were Staph. haemolyticus (11.21%) Staph. aureus (9.35%). All isolates were identified and susceptibility patterns towards about 34 different antibiotics were studied. There were 186 patients enrolled. Of all cultures, 57.5% (107) yielded one of the study pathogens. Gram-positive organisms were isolated from 83 (77.57%) of cultures, gram-negative organisms were isolated from 15 (14.02%), and 9 (8.4%) were fungal growth. From 107 gram-positive isolates, 19 samples (22.9%) gave coagulase-positive results and 64 samples (77.1%) gave negative results. All the major organisms (S. aureus, S. hominis, S. hemolytic, S. epidermidis, E. coli, Mycobacterium, and Moraxilla catarrhalis) susceptible to cephalosporins, macrolides, aminoglycosides and fluoroquinolones (levofloxacin). Tetracycline has the lowest effect on both gram-positive and gram-negative isolates. In conclusion, our findings should alert physicians on the choice of appropriate antibiotic treatment after applying AST to the identified strains and on the potential role of conjunctivitis in the spread of antibiotic-resistant pathogens. In addition, external bacterial infections of the eye were most frequently caused by the common skin bacteria. Staphylococci spp. was by far the most common bacterial pathogen.

Stable and low loss oxide layer on α-Ta (110) film for superconducting qubits

The presence of amorphous oxide layers can significantly affect the coherent time of superconducting qubits due to their high dielectric loss. Typically, the surface oxides of superconductor films exhibit lossy and unstable behavior when exposed to air. To increase the coherence time, it is essential for qubits to have stable and low dielectric loss oxides, either as barrier or passivation layers. In this study, we highlight the robust and stable nature of an amorphous tantalum oxide layer formed on α-Ta (110) film by employing chemical and structural analyses. Such kind of oxide layer forms in a self-limiting process on the surface of α-Ta (110) film in piranha solution, yielding stable thickness and steady chemical composition. Quarter-wavelength coplanar waveguide resonators are made to study the loss of this oxide. One resonator has a Qi of 3.0 × 106 in the single photon region. The Qi of most devices are higher than 2.0 × 106. Moreover, most of them are still over 1 × 106 even after exposed to air for months. Based on these findings, we propose an all-tantalum superconducting qubit utilizing such oxide as passivation layers, which possess low dielectric loss and improved stability.

Sublimation-based wafer-scale monolayer WS2 formation via self-limited thinning of few-layer WS2.

Atomically-thin monolayer WS2 is a promising channel material for next-generation Moore's nanoelectronics owing to its high theoretical room temperature electron mobility and immunity to short channel effect. The high photoluminescence (PL) quantum yield of the monolayer WS2 also makes it highly promising for future high-performance optoelectronics. However, the difficulty in strictly growing monolayer WS2, due to its non-self-limiting growth mechanism, may hinder its industrial development because of the uncontrollable growth kinetics in attaining the high uniformity in thickness and property on the wafer-scale. In this study, we report a scalable process to achieve a 4 inch wafer-scale fully-covered strictly monolayer WS2 by applying the in situ self-limited thinning of multilayer WS2 formed by sulfurization of WOx films. Through a pulsed supply of sulfur precursor vapor under a continuous H2 flow, the self-limited thinning process can effectively trim down the overgrown multilayer WS2 to the monolayer limit without damaging the remaining bottom WS2 monolayer. Density functional theory (DFT) calculations reveal that the self-limited thinning arises from the thermodynamic instability of the WS2 top layers as opposed to a stable bottom monolayer WS2 on sapphire above a vacuum sublimation temperature of WS2. The self-limited thinning approach overcomes the intrinsic limitation of conventional vapor-based growth methods in preventing the 2nd layer WS2 domain nucleation/growth. It also offers additional advantages, such as scalability, simplicity, and possibility for batch processing, thus opening up a new avenue to develop a manufacturing-viable growth technology for the preparation of a strictly-monolayer WS2 on the wafer-scale.

Analysis of Operational Characteristics of AlGaN/GaN MIS-HEMT with Different Slant-Recessed-Gate Structures

Purpose of WorkRecessed-gate metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) have emerged as a promising technology for normally-off operation because of their ability to withstand high gate voltage sweeps while maintaining low levels of leakage current [1, 2]. Despite their excellent performance, the etch to leave nanometer-thin layers of AlGaN has proven to be a significant challenge due to difficulties in precisely controlling the etching process. Achieving a positive threshold voltage (Vth) while maintaining the high electron mobility characteristic of the two-dimensional electron gas (2DEG) requires atom-level etch control. Additionally, conventional dry etching techniques can potentially cause damage, presenting a second challenge [3]. However, atomic layer etching (ALE) offers a promising solution with its potential for low damage, uniformity, and high-resolution depth control [4]. In this work, we not only focus on the ALE process to leave nanometer-thin layers of AlGaN/GaN as recessed-gate structures but also analyze the breakdown voltage characteristics of the slant-recessed gate structure.ApproachNormally-off AlGaN/GaN MIS-HEMT with a recessed gate structure was fabricated on a 6-inch commercial Si substrate by MOCVD. The process involved mesa isolation by ICP-RIE, followed by the formation of the ohmic contact (Ti/Al/Ni/Au) at 825 °C annealing for source and drain metals, and the AlGaN/GaN recessed gate structure using ALE technology by O2/BCl3 multiple cycles of oxidation and etching [5]. After the recessed-gate process, the native oxide and carbon residue were removed by a wet cleaning process and O2 plasma treatment, and then the atom layer deposition (ALD) of about 12 nm thickness Al2O3 high-dielectric layer was also deposited. The backend process included gate field plate, SiNx passivation, and contact opening. Finally, the Ni/Au metal stack was deposited as pad electrodes, as shown in Fig. 1. The specific characteristics of the fabricated recessed MIS-HEMT were Lg of 3 μm, Lgs of 5 μm, Lgd of 10 μm, and Wg of 100 μm.Results and SignificanceIn Figure 2(a) and (b), TEM profiles of the recessed gate structure were presented. Following the ALE process for the recessed gate structure, the remaining thickness of AlGaN was approximately 5.1 nm and 5.6 nm for Slant A and Slant B, respectively. Although the thickness of AlGaN remaining was similar in both cases, the slant angle of the recessed gate structure differed, significantly. Specifically, Slant A had a 65-degree recessed gate structure, while Slant B had a 45-degree recessed gate structure. In order to analyze of operational characteristics of AlGaN/GaN MIS-HEMT with different slant-recessed gate structures (Slant A and Slant B), the three-terminal OFF-state breakdown voltage (BV) was measured, as shown in Fig. 3. Recessed gate MIS-HEMT feature design of Lg/Lgd/Lgd/Wg of 3/5/10/100 μm, and VG of -10 V was used as this BV measured condition. The Slant B structure demonstrated higher breakdown voltage (BV) performance compared to the Slant A structure. Specifically, the Slant B structure exhibited a BV of 470 V at 1 μA/mm and 750 V at 1 mA/mm, while the Slant A structure had a BV of only 70 V at 1 μA/mm and 140 V at 1 mA/mm. The reason for the superior BV performance of the Slant B structure (45-degree recessed gate structure) was attributed to the gradient of the AlGaN profile, which facilitates the thin film deposition process of materials such as Al2O3 and gate metal (Ni/Au). Additionally, the Slant B structure helps to reduce the high electric field effect between the gate and drain, further contributing to its improved BV performance.[1] Y. S. Lin, Y. W. Lain, and S. S. H. Hsu, "AlGaN/GaN HEMTs With Low Leakage Current and High On/Off Current Ratio," IEEE Electron Device Letters, vol. 31, no. 2, pp. 102-104, 2010.[2] Z. Tang et al., "600-V Normally Off SiNx/AlGaN/GaN MIS-HEMT With Large Gate Swing and Low Current Collapse," IEEE Electron Device Letters, vol. 34, no. 11, pp. 1373-1375, 2013.[3] T. H. Hung, P. S. Park, S. Krishnamoorthy, D. N. Nath, and S. Rajan, "Interface Charge Engineering for Enhancement-Mode GaN MISHEMTs," IEEE Electron Device Letters, vol. 35, no. 3, pp. 312-314, 2014.[4] T. Y. Yang et al., "A Normally-Off GaN MIS-HEMT Fabricated Using Atomic Layer Etching to Improve Device Performance Uniformity for High Power Applications," IEEE Electron Device Letters, vol. 43, no. 10, pp. 1629-1632, 2022.[5] I.-H. Hwang, H.-Y. Cha, and K.-S. Seo, "Low-Damage and Self-Limiting (Al)GaN Etching Process through Atomic Layer Etching Using O2 and BCl3 Plasma," Coatings, vol. 11, no. 3, p. 268, 2021. Figure 1

Self-Expansion Based Multi-Patterning for 2D Materials Fabrication beyond the Lithographical Limit.

Two-dimensional (2D) materials are promising successors for silicon transistor channels in ultimately scaled devices, necessitating significant research efforts to study their behavior at nanoscopic length scales. Unfortunately, current research has limited itself to direct patterning approaches, which limit the achievable resolution to the diffraction limit and introduce unwanted defects into the 2D material. The potential of multi-patterning to fabricate 2D materials features with unprecedented precision and low complexity at large scale is demonstrated here. By combining lithographic patterning of a mandrel and bottom-up self-expansion, this approach enables pattern resolution one order of magnitude below the lithographical resolution. In-depth characterization of the self-expansion double patterning (SEDP) process reveals the ability to manipulate the critical dimension with nanometer precision through a self-limiting and temperature-controlled oxidation process. These results indicate that the SEDP process can regain the quality and morphology of the 2D material, as shown by high-resolution microscopy and optical spectroscopy. This approach is shown to open up new avenues for research into high-performance, ultra-scaled 2D materials devices for future electronics.

Interleukin 1β and interleukin 6 production in human immune cells is stimulated by the antibacterial compound Triclosan.

Triclosan (TCS) is an antimicrobial compound widely used in personal hygiene products such as mouthwash and toothpaste; and has been found in human blood, breast milk, and urine. Interleukin (IL)-6 and IL-1 beta (IL-1β) are pro-inflammatory cytokines regulating cell growth, tissue repair, and immune function; increased levels of each have been associated with many diseases, including cancer. Previous studies showed that TCS at concentrations between 0.05 and 5µM consistently increased the secretion of IL-1β and IL-6 from human immune cells within 24h of exposure. The current study demonstrates that this increase in secretion was not due simply to release of existing stores but was due to an increase in cellular production/levels (both secreted and intracellular levels) of each of these cytokines. Production of IL-1β and IL-6 was increased by exposure to one or more concentration of TCS at each length of exposure (10min, 30min, 6h, and 24h). TCS-induced stimulation of cytokine production was shown to be dependent on the mitogen-activated protein kinase (MAPK) p44/42 (ERK 1/2). It was also shown that these TCS-induced increases in IL-1β and IL6 production were accompanied by increased mRNA for IL-1β and IL-6. The ability of TCS to increase production indicates that rather than activating a self-limiting process of depleting cells of already existing stores of IL-1β or IL-6, TCS can stimulate a process that has the capacity to provide sustained production of these cytokines and thus may lead to chronic inflammation and its pathological consequences.

Immersion Tin Plating Enabling Reliable Wettable Flanks on QFN Packages

The automotive market increasingly uses bottom-termination IC packages, like Quad-Flat No leads (QFN) packages, for miniaturization, cost reduction and performance. QFN lead frames are electroplated with 8?12 um of tin for PCB soldering, but subsequent singulation exposes the copper-alloy lead frame at the cut edges. On these exposed lead flanks a solder fillet does not form, making Automatic Optical Inspection (AOI) of solder joints on lead-less packages not reliable. A solder fillet on lead flanks also improves the reliability of solder joints. Therefore, the automotive industry strives for a tin plated wettable flank on lead-less packages. Several approaches, e.g. dimpled or step-cut leads, to create a wettable flank are in use or development. Disadvantage of these methods is that only a part of the flank is tin-plated. Immersion tin plating processes are able to fully plate lead flanks. However, the maximum ~1.5um of standard self-limiting displacement immersion tin processes is too thin to comply with the durability requirements of automotive tin solder finishes. This contribution will discuss an immersion tin-plating process, machine concept and test results for a >2 um tin plated wettable flanks. The immersion tin plating process consist of the following process steps: 1. A high-pressure spray rinse prevents incomplete tin coverage by removing copper burrs formed during singulation. 2. A selective descaling process removes the natural copper oxide film on the exposed copper leads. 3. A selective activation process creates a high tin nucleation density to obtain a fine-grained tin layer. 4. The autocatalytic immersion tin process plates a 2 ? 3um tin layer in 45-60 minutes at 70-75oC. 5. An anti-tarnish process protects the tin layer against oxidation. Finally, rinsing and drying remove all traces of the used chemicals from the packages with tin plated flanks. A machine concept for the immersion tin-plating process is currently under development. The lead-less packages are processed directly on Standard singulation tape rings without repacking or manipulation of the packages. This enables a throughput of 20 tape rings per hour with the full package traceability required for the automotive market. Different types of QFN packages mounted on singulation tape were tin plated and subjected to standard (JEDEC J-STD-002E) solderability tests for component lead durability. Fine-grained 2-3 um thick pure tin deposit of good visual quality were obtained on the exposed QFN copper lead sidewalls with the following properties: • 0.5-1.5um residual tin layer after intermetallic formation in 8 h steam aging and 16 h oven bake. • 100% solder wetting after 6h dry bake at 150C • 100% solder wetting after 8h steam aging (93C and 80-90% RH). • 100% solder fillet height after ceramic glass test.

El endotelio sano y su disfunción en el riesgo cardiovascular

The endothelium is a monolayer of flatten cells named endothelial cells that form the inner layer of the heart, blood, and lymphatic vessels. Its function is not just as a barrier, but it is a regulator of vascular permeability and tone, hemostasis, inflammation, and angiogenesis. This review is about the general aspects of vascular endothelium and endothelial dysfunction that leads to increased vascular risk. Activation and dysfunction are discussed, considering the endothelialactivation as a self-limiting process, necessary to promote inflammation and hemostasis. Endothelial dysfunction is a pathological process in which the endothelium loses its ability for self-regulation and acquires a prothrombotic and proinflammation phenotype. Endothelial dysfunction is the initial step for atherosclerosis and increased cardiovascular risk, so the main biomarkers of endothelial dysfunction are reviewed. As basic knowledge about endothelium increases, preventive or therapeutic measures can be designed as treatment or prevention the risk of its dysfunction. Key words: Healthy endothelium; activation; endothelial; endothelial dysfunction; cardiovascular risk; atherosclerosis.

The effectiveness of past wildfire at limiting reburning is short-lived in a Mediterranean humid climate

BackgroundThe study of wildfire interactions (i.e., spread limitation and reburns) is gaining traction as a means of describing the self-limiting process of fire spread in the landscape and has important management implications but has scarcely been attempted in Europe. We examined to what extent previously burned areas restricted the development of individual large wildfires (> 500 ha) in mainland Portugal.ResultsFor the 1984–2021 period, we (1) modeled the proportion of large wildfire perimeters coinciding with transitions to shorter time since fire (TSF), i.e., locations where fire spread ceased upon encountering assumedly less flammable fuels, and (2) characterized the prevalence of different TSF in the composition of the area burned by large wildfires in relation to available TSF. Only 4% of the large wildfires did not comprise edges intersecting past wildfires. Low TSF (especially up to 8 years) resulted in large-wildfire perimeter limitation at TSF transitions. This effect was further enhanced by high historical burn probability and proximity to roadways and watercourses. Perimeter limitation did also increase under high (but not very high or extreme) fire danger, benefiting from maximum seasonal firefighting preparedness. TSF prevalence in the composition of large-wildfire area was extremely variable and thus an overall weak pattern emerged, with minimum and maximum prevalence respectively at TSF < 2 years and TSF ≥ 6 years.ConclusionsLarge wildfire limitation in Portugal is hampered by fast fuel build-up after fire, indicating a short-lived fire-hazard reduction effect under the prevailing Mediterranean humid climate of the study region. Nonetheless, such effect should be considered when planning fuel-reduction treatments and can be used opportunistically during large-wildfire suppression operations.

Fabrication and characterization of heavily doped n-type GaAs for mid-infrared plasmonics

N-type doping in GaAs is a self-limited process, rarely exceeding a carrier concentration level of 1019 cm−3. Here, we investigated the effect of intense pulsed light melting on defect distribution and activation efficiency in chalcogenide-implanted GaAs by means of positron annihilation spectroscopy and electrochemical capacitance–voltage techniques. In chalcogenide-doped GaAs, donor–vacancy clusters are mainly responsible for donor deactivation. Using positrons as a probe of atomic scale open volumes and DFT calculations, we have shown that after nanosecond pulsed light melting the main defects in heavily doped GaAs are gallium vacancies decorated with chalcogenide atoms substituting As, like VGa–nTeAs or VGa–nSAs. The distribution of defects and carriers in annealed GaAs follows the depth distribution of implanted elements before annealing and depends on the change in the solidification velocity during recrystallization.

Quasiatomic layer etching of silicon nitride enhanced by low temperature

Plasma atomic layer etching is a dry etching process using a dose step to modify a material’s surface chemistry and an etch step to remove the modified surface layer. This method of etching has certain advantages over reactive ion etch due to its self-limiting etch process for highly controllable etch depth and reduced surface roughness. In this paper, we expand upon an anisotropic, plasma atomic layer etch recipe used to etch thin films of silicon nitride, which uses an H2 plasma to modify the surface layer of the material and an SF6 etch step to remove the modified surface. Several modifications are made to the recipe, including a reduction in the pressure during the SF6 step from 500 to 20 mT, to allow compatibility with modern inductively coupled plasma-reactive ion etch systems. We then explore this recipe at low wafer temperature and find a reduction of spontaneous isotropic SF6 etching. This results in an enhancement in the self-limiting aspect of the etch process, an improvement of the etched sidewall homogeneity, and a decrease in the etched surface roughness, which has the potential to be useful for reducing optical loss in silicon nitride waveguides and other nanoscale devices made in silicon nitride.

In-Depth Understanding of Hardmetal Corrosion Performance Reveals a Path to the Electrochemical Demolition of Scrap

Recycling of hardmetal scrap is strategic for critical raw materials recovery. Available recycling processes are polluting and have a large carbon footprint. Attempts to exploit controlled corrosion failed in industrial practice, owing to self-limiting processes. We revisit the corrosion route, in view of gaining the fundamental knowledge enabling high-throughput recovery. We selected the worst-case approach of highly corrosion-resistant CoNiWC-based hardmetal grades and neutral aqueous electrolyte at room temperature. Systematic electrochemical measurements, UV–Vis spectroscopy and SEM microscopy disclosed that, even though there is no hope to overcome the self-limiting corrosion rate, nevertheless, by exploiting the mechanical action of anodic O2 evolution acting precisely at the interface between the residual active material and the corrosion film, the latter can be efficiently removed, periodically reactivating the hardmetal corrosion in a way that results in an ultra-high scrap destruction rate, of interest for real-life industrial processes.