Up to 14% of individuals with a trial of labour after caesarean birth (TOLAC) require an operative vaginal birth (OVB). We evaluated the association between forceps vs vacuum birth and severe maternal morbidity (SMM) among individuals with a TOLAC. This is a population-based cohort study of individuals with one prior caesarean birth who delivered a singleton, cephalic, term infant via OVB following a TOLAC in Canada (excluding Québec), using administrative health data (2010-2021). Procedure codes were used to identify forceps and vacuum births. Modified Poisson regression with propensity score overlap weighting was used to estimate adjusted relative risks (ARR), accounting for clinical factors. SMM included diagnoses and procedures associated with high case fatality, extended length of hospital stay and long-term disability from the birth admission to 42 days postpartum. Among 72,140 individuals with a TOLAC, 10,030 (13.9%) had an attempted operative vaginal birth (vacuum: 70.5%, forceps: 29.5%). SMM rates were higher with forceps vs vacuum (23.6 versus 14.1 per 1,000). In adjusted models, forceps use was associated with increased risk of SMM (ARR 1.58, 95% confidence interval [CI] 1.14-2.18). The two leading causes of SMM included severe hemorrhage (15.2‰ forceps vs 9.2‰ vacuum; ARR 1.55, 95%CI 1.03-2.34) and surgical complications (6.8‰ forceps vs 2.1‰ vacuum; ARR 3.55, 95%CI 1.75-7.20). Among individuals with a TOLAC, forceps birth is associated with higher risk of severe hemorrhage or surgical complications versus vacuum. Patient counseling and clinical decision-making should incorporate maternal safety by instrument attempts in tandem with attaining vaginal birth.
Digital tomosynthesis-guided vacuum-assisted breast biopsy is a standard minimally invasive technique for diagnosing focal breast lesions, with vascular complications such as pseudoaneurysm formation being exceedingly rare. We report the case of a 64-year-old postmenopausal woman who developed a 2.6-cm intramammary pseudoaneurysm in the right breast following digital tomosynthesis-guided vacuum-assisted breast biopsy for high-grade ductal carcinoma in situ adjacent to an invasive carcinoma with choriocarcinomatous differentiation, successfully treated with ultrasound-guided percutaneous thrombin injection, without complications. This case emphasizes the importance of early recognition of post-biopsy pseudoaneurysms to avoid potential hemorrhagic complications. Furthermore, this case demonstrates that ultrasound-guided breast thrombin injection is a safe and effective minimally invasive treatment option and highlights the importance of individualized therapeutic approaches to optimize outcomes.
Ultrasound-guided Vacuum-Assisted Breast Biopsy has been widely utilized as a key modality for breast nodule resection. Nevertheless, its application remains relatively contraindicated in patients who have undergone breast prosthesis placement. This study aimed to evaluate the feasibility and safety of ultrasound‑guided vacuum‑assisted breast biopsy (US‑VABB) for the resection of breast nodules ≤ 1.5 cm with BI-RADS 3-4a in patients with retroglandular breast implants. A single-center retrospective observational study was conducted on patients with breast nodules who underwent US-VABB in the Department of Ultrasound, Beijing Friendship Hospital, Capital Medical University from January 2020 to October 2024. A total of 18 patients (18 nodules) who had previously undergone breast implant placement with implants located behind the glandular tissue were included. The complete nodule resection rate, implant-related complications, postoperative pathological results, and short-term follow-up data were analyzed. Primary outcomes included complete resection rate and implant-related complications, while secondary outcomes included pathological findings and short-term follow-up results. The maximum diameter of the nodules in the 18 patients ranged from 0.5 to 1.5 cm (mean: 1.1 ± 0.4 cm), and all nodules were completely resected in a single operation, with no evidence of residual lesions on imaging. No serious complications such as breast implant rupture or leakage occurred during or after the operation. The implant rupture rate was 0% (0/18), and minor complications occurred in 16.7% of patients. Postoperative pathology revealed fibroadenoma (n=11), breast adenosis (n=3), intraductal papilloma (n=2), atypical ductal hyperplasia (n=1), and ductal carcinoma in situ (DCIS, n=1). The patient with DCIS underwent additional resection, with no residual tumor detected. These findings demonstrate that US-VABB is a safe and feasible minimally invasive approach for patients with retroglandular breast implants presenting with breast nodules ≤1.5 cm and BI-RADS 3-4a, with high resection success and low complication rates.
Vacuum-deposited lead halide perovskite thin films enable solvent-free fabrication, eliminating residual processing solvents that might compromise the long-term stability. Here, we investigate the stability of thermally evaporated mixed-cation compositions FA0.8Cs0.2PbI3 and FA0.8MA0.2PbI3 (FA+ = formamidinium and MA+ = methylammonium) under thermal and light stress. Although from a thermodynamic perspective the phase stability hierarchy is typically described as MA+ < FA+ < Cs+, with Cs-based perovskites expected to be the most stable, both compositions exhibit thermal robustness, retaining their structural, optical, and morphological properties after continuous heating at 85 °C for over 500 h. Under continuous illumination, however, distinct degradation pathways emerge: FA0.8Cs0.2PbI3 shows the largest morphological and optical changes. This is attributed to chemical inhomogeneities caused by CsI-rich segregations during crystallization, which make point defects effective triggers for photodegradation. Film homogeneity improves by partially replacing iodide with bromide. Based on these results, we selected FA0.8MA0.2PbI3 and FA0.8Cs0.2Pb-(I0.8Br0.2)3 for device fabrication and evaluated their operational stability. The resulting perovskite solar cells maintain their performance after four months of outdoor operation and withstand 900 h under continuous sun-equivalent indoor illumination at room temperature. These results demonstrate how a high-quality crystallization process can reveal the potential of MA-containing perovskite formulations for long-lived perovskite photovoltaics.
Background Vacuum-assisted closure (VAC) therapy is a well-established method that uses negative pressure to promote wound healing and enhance skin graft adherence. While globally accepted, outcomes following its use in anatomically challenging wound sites within the Bangladeshi population remain underexplored. This study aimed to assess graft take and postoperative complications following VAC-assisted skin grafting in anatomically challenging wound sites. Methods A prospective observational study was conducted at the National Institute of Burn and Plastic Surgery, Dhaka, from September 2020 to August 2021, involving 50 patients undergoing split-thickness skin grafting over difficult anatomical regions. VAC therapy was applied postoperatively at -90 to -125 mmHg for five days. Graft take was assessed on the 5th and 14th postoperative days and categorized as good (<10% loss), satisfactory (10%-25% loss), or poor (>25% loss). Postoperative complications were recorded. Statistical analyses included the chi-square test, Fisher's exact test, and Pearson's correlation, with p<0.05 considered significant. Results Complete (100%) graft take was achieved in 31 (62%) patients, while 41 (82%) demonstrated good overall graft outcomes. Complete graft take was more frequently observed in well-vascularized wound beds than in less vascularized wound beds (25/32 vs. 6/18, p=0.005). No significant correlation was observed between wound size and graft loss (r=0.0418, p=0.773). Younger patients (2-19 years) showed significantly better graft outcomes, whereas poor outcomes were confined to patients aged ≥40 years (p<0.001). Postoperative complications were minimal and transient. Conclusion VAC-assisted dressing was associated with favorable graft take and few short-term postoperative complications in anatomically challenging wound sites. However, due to the observational design, small sample size, absence of formal power analysis, and lack of a standard dressing control group, these findings should be interpreted cautiously and cannot establish relative efficacy compared with conventional dressing methods.
Postoperative systemic inflammatory response syndrome (SIRS) remains a key complication after mini-percutaneous nephrolithotomy (mini-PCNL) and is often related to elevated intrarenal pressure and bacterial translocation. Vacuum-assisted mini-PCNL (VmPCNL) has been developed to mitigate this risk through active pressure control. To evaluate the association between VmPCNL and postoperative SIRS and to identify the independent predictors of SIRS in a real-world cohort. A retrospective cohort study was conducted of patients undergoing mini-PCNL at a tertiary referral center between January 2021 and May 2025. Patients were stratified into standard mini-PCNL (SmPCNL) and VmPCNL groups. The primary endpoint was SIRS within 48 hours post-surgery. Secondary outcomes included operative time, stone-free rate (SFR), and length of hospital stay (LOS). Multivariable logistic regression was used to identify independent predictors of SIRS. A total of 136 patients were included in the study (SmPCNL, n = 78; VmPCNL, n = 58). The incidence of postoperative SIRS was significantly lower in the VmPCNL group (8.6% vs 21.8%, p = 0.036). VmPCNL was also associated with shorter operative time (median 90 minutes vs 115 minutes, p = 0.038) and reduced LOS (p = 0.012). Stone-free rates were comparable between the groups, indicating no compromise in procedural efficacy. In the multivariable analysis, VmPCNL was independently associated with a lower risk of SIRS (adjusted OR [aOR] 0.44, 95% CI 0.19-0.98, p = 0.041), while a positive preoperative urine culture was an independent risk factor (aOR 2.60, 95% CI 1.01-6.60, p = 0.045). In this real-world cohort, VmPCNL was associated with a lower SIRS incidence and improved perioperative efficiency without compromising stone-free outcomes. The mechanism may involve improved intraoperative outflow dynamics through active suction, although direct measurement of intrarenal pressure is needed to confirm this hypothesis.
The photochemical processing of organic ices is a key driver of molecular complexity in planetary atmospheres and surfaces. On Titan, diacetylene (C4H2) has been detected in the atmosphere and is expected to condense at lower altitudes, yet its subsequent solid-phase photochemistry remains poorly understood. This study investigates the vacuum ultraviolet photolysis of C4H2 ices to understand how distinct solid phases influence photoreactivity and product formation under simulated Titan conditions. Thin films of C4H2 ice in amorphous (20 K) and crystalline (20 K and 70 K) phases were irradiated for 48 hours, with chemical evolution monitored via infrared spectroscopy and temperature-programmed desorption mass spectrometry. Photolysis cross-sections were found to be phase and temperature-dependent, with the amorphous ice exhibiting the highest reactivity, while infrared spectroscopy showed evidence of crystalline phase amorphisation only in the ice irradiated at 70 K. The presence of volatile hydrocarbons including C6H2 and C8H6 was detected across all phases, while crystalline ice irradiated at 70 K yielded the most complex suite of products, with ions detected up to m/z 200. Non-volatile refractory residues with saturated and unsaturated spectral signatures remained at 300 K for all ices. The results suggest that VUV photons can drive the formation of larger, more complex organic molecules in C4H2 ices, with the solid-phase structure modulating the reaction pathways and product distribution. This solid-phase chemistry may contribute to the inventory of complex organics on Titan's surface, providing potential targets for future in situ exploration by missions such as Dragonfly.
Percutaneous vacuum-assisted mechanical thrombectomy using venovenous bypass is a potential alternative to open surgery for the removal of intracardiac and intravascular/caval thrombi. We sought to evaluate the unique role and efficacy of this procedure in the treatment of high-risk patients deemed poor candidates for surgical thrombectomy. Between May 2015 and October 2023, 40 patients underwent vacuum-assisted thrombectomy for intracardiac or caval thrombi using venovenous bypass at our medical center. Patient and case characteristics, procedural details, and postprocedural outcomes were collected retrospectively. All procedures involved a multidisciplinary approach by cardiac surgeons, interventional radiologists, and cardiac anesthesiologists. Cardiac electrophysiologists also participated in the procedures when patients needed concomitant cardiovascular implantable electronic device system extractions. Mean age of patients was 50 ± 16 years. Indications included indwelling catheter thrombus (n = 10; 25%), cardiovascular implantable electronic device infection (n = 12, 30%), tricuspid endocarditis (n = 8, 20%), and bland and tumor thrombus (n = 11, 28%, n = 7, 18%, respectively). Successful removal rate (>70% of thrombus removed) was 85% (n = 34). Interventional adjuncts included cardiovascular implantable electronic device lead extraction (n = 10, 25%) and snaring from contralateral access site (n = 7, 18%). In-hospital and 30-day mortality were 5% (n = 2) and 8% (n = 3), respectively. Complications included postoperative red blood cell transfusion (n = 5, 13%), pulmonary embolism (n = 2, 5%), and recurrent thrombosis (n = 2, 5%). Median total follow-up time was 16 ± 3 months, with either complete resolution or decreased burden of residual thrombus. Vacuum-assisted thrombectomy is a rapid, effective, and safe technique when treating critically ill patients with acute intracardiac and caval thrombi and vegetation. It can be a highly valuable adjunct when treating poor candidates for open cardiovascular surgery.
Indoor dust is an important exposure pathway for potentially toxic elements (PTEs) in industrial hotspots such as the Meža Valley (Slovenia), impacted by centuries of Pb-Zn mining/smelting and ongoing metallurgical activities. This study is the first to examine household dust from homes of children participating in biomonitoring, providing a unique opportunity to directly assess the relationship between indoor contamination and biomonitoring outcomes. Household vacuum dust from 27 homes (Upper Meža Valley, n = 13; Lower Meža Valley, n = 14) was analysed for 12 metal(loid)s. Statistical analyses identified three dominant source-related groups: (1) Pb-Zn-Cd (legacy mining/smelting), (2) Cu-Sn (Pb recycling), and (3) Cr-Ni-Mo (steel production), indicating a mixed anthropogenic fingerprint across the valley. Health risk assessment of PTEs indicates that ingestion is the primary exposure pathway, with children facing 7-12 times higher non-carcinogenic risks than adults. Children's blood lead levels (BLLs) were generally low (75th percentile = 31 µg L⁻¹), although 6 of 27 exceeded the CDC blood lead reference value of 35 µg L⁻¹. Lead concentrations in household dust significantly predicted BLL variability (adjusted R² ≈ 0.23), highlighting indoor dust as a relevant contributor to internal lead exposure. Cumulative cancer risks remained within acceptable regulatory limits under both worst-case (100% Cr(VI), 9.03 × 10⁻⁵) and more realistic (5% Cr(VI), 1.97 × 10⁻⁵) scenarios. Persistent indoor contamination following the 2023 flooding events, despite ongoing remediation efforts, underscores the need for area-wide mitigation strategies and continued environmental and health monitoring to limit PTE transfer into indoor environments.
Autologous fat transfer (AFT) is an emerging option for total breast reconstruction. To improve graft survival, perioperative external vacuum expansion (EVE) is used to optimise recipient-site environment. However, the efficacy of EVE and its treatment burden on women needs consideration. This interim analysis of a multicentre randomised controlled trial (RCT) evaluates the effect of EVE on volumetric outcomes and safety. Women undergoing total breast reconstruction with AFT were randomised 2:1 to perioperative EVE or no EVE. All participants underwent three AFT sessions followed by magnetic resonance imaging (MRI)-based volumetric assessment at six months. Primary outcomes were percentage augmentation and graft retention. Secondary outcomes included (serious) adverse events (SAEs). Quality-of-life (QoL) outcomes were not analysed in this interim analysis, as reconstruction was ongoing. Fifty-three participants were included (EVE, N = 32; control, N = 21). Mean augmentation was 190.7% with EVE versus 176.4% without (adjusted difference 14.6%; 95% CI -80.0 to 109.1; p = 0.757). Graft retention was 39.3% and 34.9%, respectively (difference 4.5%; 95% CI -6.4 to 15.4; p = 0.405). Both outcomes showed no statistically significant between-group differences. The EVE group experienced more AEs (22 AEs and 5 SAEs) compared with the control group (three AEs and two SAEs), which were predominantly skin-related complications. Perioperative EVE use did not yield significant improvements in augmentation or graft retention; however, it was associated with higher treatment burden and more (S)AEs. Final analyses of our ongoing RCT, incorporating patient-reported QoL outcomes are still awaited. Based on this interim analysis, the clinical benefit of EVE in reconstructive settings remains uncertain and warrants additional research.
Environmental monitoring of viral pathogens will be a critical tool to prevent morbidity and mortality in future pandemics and yearly disease cycles. One approach in early stages of utilization is monitoring viruses from building dust. To date, these efforts have primarily used PCR-based methods to target individual viruses. Additional methods that can identify multiple viruses simultaneously, and in a semi-quantitative manner, would increase the efficiency and utility of these efforts. The goal of this project was to evaluate a whole-genome, hybrid-capture based high-throughput sequencing approach for measuring pathogens in building dust. We utilized the Illumina Viral Surveillance Panel v2 to enrich for targeted amplification of viral nucleic acid followed by sequencing in 27 samples from school, university, and professional settings. We identified 54 viruses that included pathogens such as SARS-CoV-2, influenza, adenovirus, norovirus, cytomegalovirus, Epstein-Barr virus, and more. Three of the viruses that are known to be associated with childhood infection were significantly more prevalent in child-associated settings than in buildings primarily occupied by adults (fdr p<0.05). A total of 85% of all collected samples contained at least one rhinovirus. Abundances of SARS-CoV-2 and influenza A viruses were estimated with traditional qPCR methods, and were correlated with relative abundances estimated from the sequencing data (R=0.76 and 0.42, p=0.000005 and 0.03, respectively). The methods utilized here measure nucleic acid and does not indicate viability. Overall, our results demonstrate a novel environmental surveillance technique for simultaneous and semi-quantitative measurement of multiple viral pathogens using building dust that can help us better understand viral spread, inform public health policy, and promote health.
Aspiration thrombectomy is a widely adopted acute ischemic stroke treatment with low complication rates. Traditional aspiration catheter delivery relies on microcatheters and microwires. Their removal before active aspiration has been observed to incidentally promote clot engagement; however, the mechanical basis and clinical relevance of this interaction remain poorly understood. Recently developed internal delivery catheters (DCs), such as Tenzing (Route 92 Medical), closely match the aspiration catheter lumen and appear to accentuate this effect, enabling quantification of the underlying mechanism. A physiologic benchtop cerebrovascular model was used to measure vacuum pressures during DC withdrawal and assess their effect on clot interaction. Test configurations included 3 aspiration catheter sizes (0.054″, 0.070″, 0.088″) tested with and without a Tenzing DC using synthetic thrombi. Vacuum pressure data were synchronized with fluoroscopic imaging and correlated with clot engagement and ingestion outcomes. Institutional Review Board approval and patient consent were not required for this in vitro study. Tenzing DC withdrawal produced a brief but substantial negative pressure spike (0.45-1.81 seconds), reaching 52% to 97% of maximum syringe vacuum (-560 mm Hg). This transient vacuum coincided with clot motion before active aspiration. Overall rates of successful clot capture were similar with and without DC use; however, DC-assisted trials showed a higher incidence of corked and fully ingested clots (P < .05), whereas aspiration catheter-only trials more frequently resulted in full clot aspiration. Withdrawal of a closely size-matched DC generates a previously unquantified transient vacuum that initiates preaspiration clot engagement. This study identifies synthetic aperture aspiration as a mechanism creating a localized low-pressure field that may promote early clot mobilization and wall detachment before active suction. While DC withdrawal likely contributes to clot engagement, the primary value of a DC remains safe navigation and device delivery.
Chemical proteomics approaches often yield low peptide recovery because they aim to enrich low-abundance proteins. Poor sample handling further reduces recovery through peptide adsorption to plastic surfaces and losses due to vacuum evaporation. We systematically mapped these losses across buffers, volumes, plastics and pH, then developed an Evotip-compatible handling protocol that minimizes adsorption and removes the need for vacuum evaporation. Losses to plastic adsorption and vacuum evaporation were most apparent at low inputs (< 200 ng) and with larger volumes (> 20 µL) but were also dependent on acidification as well as the buffer and plastic used. The optimized workflow: direct acidification of peptides, frozen storage if needed, and direct loading onto Evotips, resulted in up to ∼90-fold gains versus workflows incorporating vacuum concentration steps, a common practice in proteomics sample preparation, when peptide input was limited to 10 ng. This optimized sample handling method enables high-throughput chemical proteomics by reducing manual handling steps and enables the characterization of low abundance proteins previously lost during sample preparation.
Low-density foams are of significant interest in inertial confinement fusion (ICF), with potential applications as fuel carriers, ablation layers, or as a hohlraum filling material. Despite their potential, the shock response of these materials remains poorly characterized, limiting the accuracy of hydrodynamic simulations. Here we report experimental measurements of the equation of state for 90mg/cm^{3} silica (SiO_{2}) aerogel foam under laser-driven shock compression, conducted at the GEKKO XII laser facility. Shock pressures between 50 and 160 GPa were achieved, and the corresponding states were determined using standard impedance-matching techniques with a quartz reference material. Initial measurements appeared to underestimate the foam shock velocity relative to predictions by the Quotidian Equation of State (QEOS) model. Experimental diagnostics indicated the presence of a vacuum gap between the reference material and the foam. The vacuum gaps were characterized, and one-dimensional radiation-hydrodynamic simulations were conducted to estimate their impact on the measured shock velocity. After applying simulation-based corrections, the experimental Hugoniot aligns closely with QEOS predictions, supporting the model's applicability to low-density foams.
In this work, we present a simple protocol for processing and analyzing multi-peak scanning tunneling microscope light emission (STM-LE) spectra obtained using an all-optical setup integrated into a standard low temperature, ultrahigh vacuum, scanning tunneling microscope system. The method involves measuring the polarization dependence of the STM-LE spectra and evaluating the localized surface plasmon confinement length to determine the presence and orientation of dipole emitter/s. We apply this technique to the STM-LE from Au-tip/Au(111) surface and Au-tip/Ag(111) surface systems. The observed spectra contain multiple peaks that cannot be described by a single confinement length, indicating the presence of multiple dipole emissions arising from electrical excitation within the tip-surface junction. The polarization of the STM-LE from distinct dipoles reveals that these dipoles have different orientations. Our work demonstrates that a simple and all-optical addition to a standard ultrahigh vacuum STM system can be used to obtain more in-depth information from the STM-LE spectra.
Counterions and the solvent environment are critical factors determining the electrical properties of DNA. Previous studies have reported the effects of Na+ ion concentration variations and solvent environments on the electrical conductivity of B-DNA. However, the mechanism by which they exert their influence on the drug-DNA complex remains unclear. This model integrates density functional theory and the nonequilibrium Green's function formalism to explore the impact of Na+ ions on the electrical properties of three drug-DNA complexes in both aqueous and vacuum environments. By minimizing the energy, Na+ ions are added to the drug-DNA complexes to render them electrically neutral. Subsequently, the electrical properties of the three DNA molecules are calculated under neutral conditions and after randomly removing one Na+ ion in different solvent environments to investigate the effects of the solvent environment and Na+ ions. The results show that the presence of Na+ hinders charge transport at the HOMO level both in aqueous solvent and vacuum. The removal of one Na+ ion from each of the three complexes leads to an increase in molecular conductivity and charge transfer efficiency, among which the Noga-DNA complex is particularly significantly affected by Na+ ions in the aqueous environment.
Cryo-scanning electron microscopy (cryo-SEM) was used to examine intact frozen-fractured eggs from five avian species-quail, hen, duck, turkey, and goose-spanning two taxonomic orders (Galliformes and Anseriformes) and a wide range of egg sizes. Whole eggs were frozen in liquid nitrogen within 24 h of laying, fractured at cryogenic temperature, and observed in the frozen-hydrated state after vacuum sublimation and gold coating. Multiple structural regions were examined, including yolk spheres, the albumen body, the shell-shell membrane-albumen interface, and the yolk-vitelline membrane-albumen interface where suitable fracture surfaces were available. Yolk spheres displayed a conserved polyhedral close-packing geometry across species, with larger eggs generally showing larger yolk sphere dimensions. The frozen albumen displayed species-dependent ice crystal morphologies: an isotropic spongy network in quail, fine parallel lamellae in hen, coarser lamellae in turkey, a multi-domain columnar-dendritic pattern in duck, and coarse lamellae in goose. These morphological differences did not simply scale with egg size and suggest that species-dependent differences in albumen composition and freezing behavior may influence ice crystal growth during cryogenic fixation. Because freezing rate and egg geometry were not independently controlled, the observed structures should be interpreted as cryo-fixed freezing morphologies rather than direct representations of unfrozen albumen microstructure. To our knowledge, systematic cryo-SEM comparison of albumen freezing morphology within intact avian eggs has not previously been reported. This study provides a rare comparative cryo-SEM atlas of intact frozen-fractured avian eggs and a morphological basis for future controlled investigations of albumen composition, freezing behavior, and ice crystal growth.
We developed a robust vacuum system for separating CH4, CO, and CO2 from laboratory-prepared and natural gaseous samples for radiocarbon (14C) and stable carbon isotope ratio (δ13C) analyses. The system is unique in its ability to isolate all three gases from a single sample without cross-contamination. While CH4 and CO2 are major greenhouse gases, atmospheric CO is a toxic air pollutant primarily emitted from incomplete combustion processes. As these species have different sources, tracing of individual gases needs efficient separation methods for δ13C- and 14C-based source identifications. The developed system achieves extraction efficiencies of ∼95-100% for all three gases, with negligible background contribution to the isotopic ratios and no detectable intermixing. System performance is demonstrated using synthetic air mixtures with controlled gas concentrations, as well as natural air samples collected from diverse environmental settings. The results confirm that the system is well suited for high-precision δ13C and 14C measurements of CO2, CH4, and CO in complex air matrices.
This Letter uncovers five distinct charge transport modes and their transitions in dual-energy electron beam diodes. We via first-principle particle-in-cell (PIC) simulations establish that the specific mode (e.g., space-charge oscillations) and the current transmitted characteristics are essentially governed by the interplay between the electron beam energy and the injected current density. The effective space-charge-limited (SCL) current (lower than the conventional SCL threshold) is unveiled due to the coupled interactions between two electron beams. A generalized analysis is conducted for n-component electron beams, and a theoretical piecewise function for the transmitted current density is proposed, which agrees well with the PIC results under designed conditions. The discovery provides a mechanistic picture of multiple electron beam transport in diodes, paving the way for novel designs of high-performance modern vacuum electronic devices.
The global impact of the COVID-19 pandemic has instigated a profound public health crisis, particularly affecting professionals like dentists who, due to their close interaction with saliva-a potential viral reservoir-and the aerosols generated during specific procedures, face elevated risks of infection. To mitigate this, the Centers for Disease Control and Prevention (CDC) and the Philippine Dental Association (PDA) have established guidelines for averting cross-infection in dental settings. This study, conducted in an urbanized Metro Manila City, delves into the infection control practices of dentists amid the pandemic. Dentists from a Metro Manila city dental chapter were invited to participate in an online survey (Google Forms) consisting of participants' demographics, patient triage, engineering, administrative controls, disinfection personal hygiene, personal protective equipment (PPE), and waste management practices. Descriptive statistics, employing frequency distributions and percentages, summarized the dentists' adherence to infection control protocols. Out of forty-nine respondents (49), the majority (92%) provided their teams' orientation on COVID-19 infection control protocols before reopening. Notably, 57% deferred elective procedures and 43% postponed aerosol-generating procedures (AGPs). Only 39% utilized rubber dam isolation during AGPs. Most respondents reported full implementation of recommended administrative controls during the pandemic, with 92% isolating their treatment areas from other parts of the clinic. Most respondents adopted high-efficiency particulate air (HEPA) filtration units (82%) as one of their clinic's engineering controls, and an extraoral vacuum machine, accounting for 71% of the respondents. The most common disinfection product used by the participants was alcohol, which was at 94%. Additionally, over 90% adhered to all recommended hand hygiene practices for both dental staff and patients. For the waste management protocols, only 55% of the respondents have their infectious waste collected by third-party Treatment Storage and Disposal (TSD) facilities. The data shows that with the guidelines posted by both the PDA and CDC, the city's dental practitioners could still provide services to the community in the safest manner at the time by being updated and following the infection control practices suggested by both organizations. Although some areas could have been improved, such as third-party waste management and the utilization of RT-PCR testing, some of these problems could have been attributed to the lack of availability in their areas.