bluuebunny/crossref_metadata_2025 huggingface dataset:
Determinants of physical activity in older adults: an umbrella review protocol
Authors: D’Amore Cassandra , Bhatnagar Neera , Kirkwood Renata , Griffith Lauren E. , Richardson Julie , Beauchamp Marla
Published: June 2021

Objective:

The aim of this review is to summarize the evidence for determinants of physical activity in older adults.

Introduction:

Physical activity is an important predictor of multi-morbidity, falls, and cognitive decline in older adulthood. Understanding what influences older adults’ physical activity behavior is an important first step for guiding effective interventions for promoting physical activity in this population.

Inclusion criteria:

This umbrella review will include systematic reviews (including scoping reviews) reporting on the relationship between determinants (also referred to as correlates or factors), measured by either self-report or direct measurement, and physical activity in adults ≥60 years.

Methods:

A systematic search of six databases will be completed in MEDLINE, Embase, CINAHL, Cochrane Library, PsycINFO, and AgeLine. Two independent reviewers will screen titles, abstracts, and full-text articles, and perform data extraction and quality assessment. Evidence for determinants of physical activity will be synthesized using the socio-ecological model. If possible, evidence will be compared by study design, type of physical activity, outcome measure used, setting, and sex.

Systematic review registration:

PROSPERO CRD42020159332
Effectiveness and usability of mobile health applications for medication adherence in patients with heart failure: a systematic review protocol
Authors: de Barros Kátia Adriana Alves Leite , Martins Maria Auxiliadora Parreiras , Praxedes Marcus Fernando da Silva , Ribeiro Antônio Luiz Pinho
Published: June 2021

Objective:

This review will assess the effectiveness and usability of mobile health applications to improve medication adherence in patients with heart failure.

Introduction:

Poor medication adherence by heart failure patients is a major cause of negative clinical outcomes, high rates of hospital readmissions, and death, thereby increasing costs for patients and the health care system. Several studies have shown that the use of mobile health applications improves self-care by heart failure patients, including medication adherence. Therefore, gathering evidence on these studies will help researchers and clinicians understand the impact of such interventions on patient care.

Inclusion criteria:

Eligible studies will evaluate medication adherence in participants aged ≥18 years diagnosed with heart failure who are using app-based (software) interventions. Experimental and observational studies will be included. We will exclude studies with interventions that used mobile applications without functionality to assist the user in organizing and taking their medications.

Methods:

Articles published from database inception to the present day, without language restrictions, will be selected from Embase, MEDLINE, LILACS, Scopus, Web of Science, CINAHL, and the Cochrane Library. Two independent reviewers will screen articles, assess methodological quality, and extract data using JBI assessment and extraction instruments. Discrepancies will be solved by consensus and a third reviewer will be consulted if necessary. A narrative synthesis of findings will be presented, and statistical analysis will be used when appropriate.

Systematic review registration number:

PROSPERO CRD42020147816
Impact on Anode Performance of Lithium-Ion Batteries by Deep Cryogenic Treated SnSb/C Nanofiber Derived From Inorganic Precursors
Authors: Chen Yu , Yan Yuan , Sun Gang , Liu Wei , Ma Min , Zhou Huimin , Cheng Lu , Zhang Hualong , Xia Xin
Published: June 2021

The major obstacle prohibiting the practical application of Sn-based anodes is drastic volume variation during cycling processes. Here, polyacrylonitrile (PAN) was acted as a carbon source, and stannic chloride pentahydrate (SnCl4·5H2O) and antimony chloride (SbCl3) were used as SnSb precursors. SnSb/C nanofibers were prepared via simple electrospinning, deep cryogenic treatment, and carbonization, and it is applied in anode materials for lithium-ion batteries (LIBs) to achieve excellent cycle performance (115.5% capacity retention for 100 cycles). The improvement of electrochemical performance is mainly attributed to the synergistic effect of deep cryogenic treated special SnSb/C nanofibers precursor. In the deep cryogenic treatment process, the crystalline water in the precursor has a pore-forming effect, and the porous nanofiber structure leads to the phenomenon of capacity increase. The above results indicate that comprehensive consideration of deep cryogenic treatment and nanofiber precursors is a new idea to enhance the electrochemical performance of LIBs anode materials.
Investigation and Optimization of Diesel Engine Outputs Under Undi Biodiesel-Diesel Strategies
Authors: Madane Pravin Ashok , Bhowmik Subrata , Panua Rajsekhar , Varma P. Sandeep , Paul Abhishek
Published: June 2021

The present investigation accentuates the impact of Undi biodiesel blended diesel on combustion, performance, and exhaust fume profiles of a single-cylinder, four-stroke diesel engine. Five Undi biodiesel-diesel blends were prepared and tested at four variable loads over a constant speed of 1500 (±10) rpm. The Undi biodiesel incorporation to diesel notably improved the in-cylinder pressure and heat release rate (HRR) of the engine. The higher amount of Undi biodiesel addition enhanced the brake thermal efficiency (BTE) and brake specific energy consumption (BSEC) of the engine. In addition, the Undi biodiesel facilitated the reduction of the major pollutants, such as unburned hydrocarbon (UHC), carbon monoxide, and particulate matter (PM) emissions with slightly higher oxides of nitrogen emissions of the engine. To this end, a trade-off study was introduced to locate the favorable diesel engine operating conditions under Undi biodiesel-diesel strategies. The optimal results of the engine operation were found to be 32.65% of brake thermal efficiency, 1.21 g/kWh of brake specific cumulated oxides of nitrogen and unburned hydrocarbon, 0.94 g/kWh of brake specific carbon monoxide (BSCO), and 0.32 g/kWh of brake specific particulate matter (BSPM) for 50% (by volume) Undi biodiesel blend at 5.6 bar brake mean effective pressure (BMEP) with a relative closeness value of 0.978, which brings up the pertinence of the trade-off study in diesel engine platforms.
Optimizing well-depth sequences for Schroeder diffusers using machine learning
Authors: Selugar Priyam , Azad Hassan
Published: June 2021

Around mid-1970, Schroeder introduced a mathematical theory to generate sequences, which can compute the “depth of the Schroeder diffuser”. A Schroeder diffuser is a design consisting of a number of wells of different “depths,” which propagates sound energy in different directions. The Schroeder diffuser provides the ability to create an optimal scattering of the same sound energy in different diffraction lobes. This paper aims to exploit this property and optimize well-depth sequences from Schroeder diffuser using machine learning techniques. With the advent of machine learning and parallel computing, the optimization of sequences and the iterative process to select the optimal pattern of sequence can be done more efficiently. Hence, the primary focus of this paper is to come up with a machine learning model that predicts the scattered reflections from a random well-depth sequence surface and evaluates the quality of the scattered reflections using a diffusion coefficient. The model tries to achieve optimum diffuser properties by adjusting the sequence. The boundary element method can be used for computing the diffusion coefficient. The diffusion coefficient parameter determines the quality of the diffuser and can be calculated at ⅓ Octave frequency bands.
Relationships between ratings and calculated loudness values for sonic booms at low levels
Authors: Töpken Stephan , van de Par Steven
Published: June 2021

Due to progress in aircraft design, the sonic boom produced by supersonic aircraft may be reduced considerably in the future and the subjective response of humans to future low sonic boom signatures is currently under investigation. In the frame of the RUMBLE project, loudness and short-term ratings of different recordings and simulations of classical booms and potential future boom sounds were collected. The time signals of the signatures were differing in shape but were confined in maximum overpressure and the A-weighted sound exposure level (ASEL) to the range foreseen for future low boom aircraft. Besides a high correlation with the ASEL, the short-term annoyance ratings were also highly correlated to the loudness ratings, suggesting that loudness was the underlying factor for short-term annoyance in the laboratory experiments. Therefore, loudness values were calculated with loudness models from the current ISO 532-1 and 532-2 standard in an attempt to predict the annoyance ratings. The correlation coefficients between short-term annoyance ratings and loudness model values are similar to those between ratings and level based measures (e.g., weighted SELs). For the loudness model according to the ISO 532-1 standard, the correlation coefficient is even slightly higher that than for ASEL.
Simulated X-59 on- and off-design sonic boom levels in realistic atmospheres for noise dose range estimation
Authors: Doebler William , Loubeau Alexandra , Lonzaga Joel B.
Published: June 2021

NASA is planning several community noise surveys across the USA using the X-59 low-boom aircraft. These surveys require a range of noise levels to resolve a dose-response relationship. The X-59 was designed to produce a shaped sonic boom with a Stevens’ Perceived Level (PL) of 75 dB or less across the boom carpet in a standard atmosphere. However, the X-59’s flight condition can be adjusted to produce levels other than 75 PLdB to obtain a range of doses during community testing. Simulated nearfield pressure waveforms of the X-59 C612A in its on-design condition (Mach 1.4 at 53 200 ft) and an off-design condition at a lower altitude (Mach 1.4 at 46 000 ft) were propagated using PCBoom through realistic atmospheres over the span of one year at several locations across the country. The predicted on-design and off-design boom levels and carpet widths are presented, resulting in a preliminary estimate of the dose range that the X-59 may produce. Future work is planned with additional off-design conditions to assess the true capable dose range of the X-59.
Evaluating speech enhancement for cochlear implants using a web application
Authors: Goldsworthy Raymond L. , Bissmeyer Susan , Swaminathan Jayaganesh
Published: June 2021

People who suffer from hearing loss struggle to maintain social relationships, which diminishes their quality of life. As technology progresses, video calls are an increasingly common way of communicating with family and friends. This trend has been accelerated by the rapid rise of software for video conferencing to support communication during the past year of pandemic restrictions. Consequently, using the same media devices that are used for video calls is an ecologically valid way of assessing hearing. This presentation describes a web application for conducting remote hearing assessments on any media device. The features of the web application will be introduced, and research results will be presented from a study of speech enhancement for cochlear implants. Consonant perception is innately challenging for listeners with hearing loss and transmission of speech over communication channels further deteriorates the acoustics of consonants. We hypothesized that consonant enhancement at the source would improve identification. The results indicate that transient emphasis does improve consonant identification for cochlear implant users while preserving their vowel identification accuracy. Discussion will consider general use of hearing assessments using media devices that people use in their daily lives.
Testing phonetic and phonological learning skills remotely: Common challenges and solutions
Authors: Spinu Laura , Muscalu Laura , Wallace Julia
Published: June 2021

We compared monolinguals' and bilinguals' ability to learn an artificial accent of English upon brief initial exposure in an online experiment (n = 40) using the pavlovia.org platform. Our findings replicated those of an earlier experiment conducted in the lab (n = 60), leading us to conclude that remote testing can offer a promising alternative to traditional lab testing in this particular line of research.
Rhotics and affricates in Sursilvan Romansh: Evidence from remote preliminary research on an under-documented language
Authors: Wright Ashlyn
Published: June 2021

Based on my remote phonetic documentation of the Sursilvan variety of Romansh (roh-sul, Gallo-Iberian, Switzerland), I propose a phonetic inventory and present acoustic analyses of variation in rhotics [ʁ] & [χ] as well as contrasts and coarticulation within the affricate system. This contribution to the scarce documentation on Sursilvan Romansh highlights the opportunities presented by remote methods for preliminary research on under-documented language varieties.
Directional sound field decay analysis in coupled spaces
Authors: Berzborn Marco , Balint Jamilla , Vorlaender Michael
Published: June 2021

Multi-exponential energy decays—showing a distinct curvature in the measured decay curve—are a well known phenomenon in coupled spaces if both spaces exhibit different reverberation times due to their specific absorption characteristics or volumes. Recently, Berzborn et al. (2019) investigated directional energy decay curves—calculated from a plane wave decomposition of the sound field—as an analysis framework for the angular distribution of energy during the decay process in reverberation rooms. In this contribution, we investigate the directional characteristics of the energy decay in two rooms connected by a door. Spherical microphone array measurements at two different receiver positions and coupling areas were performed. Results indicate a distinct anisotropic energy decay in the room with the shorter reverberation time, showing a decreased isotropy in the late decay process compared to the early part.
Real-time cavitation control and monitoring for focused ultrasound blood-brain barrier opening via dB-based subject calibrated feedback controller
Authors: Chien Chih-Yen
Published: June 2021

With proposed the dB-based subject calibrated feedback controller, we can achieve different levels of blood-brain barrier opening by adjusting the desired dB level.
Nonlinear thermoacoustic instability investigation on ammonia-hydrogen combustion in a longitudinal combustor with double-ring inlets
Authors: Zhao Dan , Ni Siliang , Guan Di
Published: June 2021

The greenhouse effect induced by the combustion of hydrocarbon fuel is an urgent environmental problem. Ammonia gas, as a renewable energy with a high proportion of hydrogen content, can achieve zero CO2 emission. In order to ignite ammonia and obtain continual flame, a partial premix entry condition of NH3/H2/O2 with double-ring inlets is adopted. The RNG k-ε model and EDC model are used to analyse the self-excited oscillation and the total heat release. After the numerical results and experimental data are validated, the following aspects are investigated: (1) total mass flow rate; (2) mass fraction of hydrogen; (3) mass flow ratio of inlets; and (4) the temperature of the heat exchanger. The results are compared with the traditional single-ring structure under the same condition. It is found that the exothermic heat of double-ring structure increases by 98.7% on average. The frequency of intermittent oscillation increases with the decrease in HN3 proportion. When pure hydrogen is passed through the outer ring, the combustion limit can be greatly expanded even if the inlet mass fraction of hydrogen is very small. This study contributes to provide an alternative method to enhance ammonia combustion and improve its flammability limit.
Reducing hearing loss through safe listening: An initiative of the World Health Organization
Authors: Chadha Shelly
Published: June 2021

Globally, over one billion people are estimated to be at risk of hearing loss due to the common practice of listening to loud sounds in recreational settings. Given the current situation and projected rise in need for hearing care over the coming decades, prevention of hearing loss has become an urgent public health need. To address this, WHO, in 2015, launched the Make Listening Safe initiative. Focused on adolescents and young adults, this aims at raising awareness among this group about the need for and the means of safe listening. At the same time, it works to influence societal and political change so as to facilitate the practice of safe listening. Toward this end, WHO is working to ensure that personal devices such as smartphones and MP3 players include safe listening features and that entertainment venues can create a safe listening environment. Through this talk, WHO will share information of its evidence-based recommendations for safe listening, as well as efforts to promote their implementation.
Creating problems by problem solving: A conversation on how “single problem focus” can ignore or even cascade into undesired, and potentially harmful acoustical issues
Authors: Good Kenneth W. , Schnitta Bonnie
Published: June 2021

A significant part of our profession is translation. It is far too easy to provide the exact right answer to the wrong question and the right solutions are often beyond the problem presented. This conversation will discuss cases where misunderstanding or misleading information was followed by folks asking the wrong question. These examples did or could have resulted in unsatisfactory outcomes at best and deadly outcomes at worst.
Non-occupational noise exposure in the United States: A review
Authors: Fink Daniel
Published: June 2021

That occupational noise exposure causes hearing loss has long been known, but non-occupational noise exposure was generally not recognized as causing hearing loss until the 1960s. Audiometric evaluation of populations not exposed to occupational noise was used to establish normal hearing baselines for workers compensation purposes. Audiometery in these groups, and in isolated populations not exposed to loud noise, suggested that hearing was preserved without noise exposure. The word sociocusis was used to describe non-occupational hearing loss. There are no federal recommendations, guidelines, or standards for non-occupational noise exposure. Perhaps because of a misconception that the 85 A-weighted decibel recommended occupational noise exposure limit is safe for the public without time limit, everyday noise exposure appears to have increased. Noise-induced hearing loss (NIHL) has become a major public health problem in the U.S., with approximately 20% of adolescents age 12–19 and 25% of adults age 20–69 having NIHL Common sources of non-occupational noise exposure include transportation noise, music and entertainment including personal listening devices, restaurant noise, kitchen appliances and power tools, hobbies, and sports. Efforts to reduce non-occupational noise exposure must include public education and the promulgation and enforcement of standards for non-occupational noise exposure.
A wavelength-dependent radiator for improved non-contact measurements of elastodynamic guided waves
Authors: Hakoda Christopher , Pantea Cristian , Chillara Vamshi K.
Published: June 2021

Air-coupled transducers are great for making non-contact measurements of the acoustic leakage emitted from ultrasonic guided waves that travel within an elastic solid. Often times, however, this measured acoustic leakage has a low signal amplitude which only gets worse the further away you position the air-coupled transducer. To improve the measured signal amplitude, we have designed a simple radiator that more efficiently converts elastodynamic wave energy into acoustic wave energy. The radiator is wavelength-dependent which allows for mode-dependent sensitivity and it can be made out of well-understood, durable materials. The end result of this is that the air-coupled transducer can be positioned further away in a safer environment or the increased signal strength can be used to improve the signal-to-noise ratio in a noisy environment. In this presentation, we will discuss our preliminary radiator design, discuss the various parameters that affect its performance and simulation results that demonstrate its effectiveness when compared to your typical acoustic leakage.
Total multiple scattering cross section evaluation using convolutional neural networks for forward and inverse designs of acoustic metamaterials
Authors: Tran Thang , Khatami Ehsan , Amirkulova Feruza
Published: June 2021

We design convolutional neural network models to simulate acoustic multiple scattering from cylindrical structures. The models are trained on data generated by multiple scattering theory to approximate total scattering cross section (TSCS) at different wavenumbers. In our first case study, the input of convolutional neural networks are binary images of positions of the cylinders, and the output is the TSCS, evaluated at eleven discrete values of wavenumber. We consider different planar configurations with five different numbers of cylinders ranging from 2 to 10. Our results show a good correspondence between predicted values and actual TSCS. However, we find that the training accuracy decreases as the number of scatterers increases. In a second case study, we develop convolutional autoencoder models, which take scatterer configuration images as input and, in the process of reproducing the same configurations at the output, reduces the dimensionality of the data to a small number of latent variables. We then use the latent variables in various inverse designs, producing scatterer configurations given values of TSCS. Despite its limitations the autoencoder proves to be a promising tool in searching for desired scatterer configuration without expensive computational cost.
Framing undergraduate education approaches in speech and hearing sciences—Liberal arts, vocational, or skill-set oriented?
Authors: Lee Adrian KC
Published: June 2021

Human communication is complex and the academic disciplines associated with speech and hearing sciences are necessarily interdisciplinary. In the past few years, the role of and models for undergraduate education in this discipline have been debated within the American Speech-Language-Hearing Association (ASHA) and the Council of Academic Programs in Communication Sciences and Disorders (CAPCSD). Traditionally, these undergraduate programs are collectively referred to as Communication Sciences and Disorders (CSD) education, and historically they employed a broad educational perspective based in the liberal arts and sciences. However, many programs today have evolved to focus more primarily on pre-professional education in the clinical fields of speech-language pathology and audiology. From the standpoint of education in acoustics, how should we frame our undergraduate courses to provide the necessary broad general knowledge and skills while satisfying an expectation of vocational preparation from students and other clinically oriented professional organizations? In this talk, I argue that a skill-set oriented approach may be more suitable to prepare CSD undergraduates for a variety of career paths.
Teaching about acoustic measurement and analysis using smartphones
Authors: Lentz Jennifer , Yun Donghyeon
Published: June 2021

Because smartphones are ubiquitous in modern society, they can serve as excellent mobile tools for students to explore aspects of acoustic measurements in and outside of the classroom. In this talk, I will present a set of lab activities based on smartphones which have allowed students studying speech, language and hearing sciences to use their smartphones as a sound level meter and waveform/spectrum analyzer to measure sounds in their daily lives. In group work, students can compare results from apps installed on different cell phone platforms with measures from a calibrated sound level meter, thereby giving them an opportunity to explore the strengths and limitations of cell phones as measurement devices. This presentation will also discuss how lab reports and classroom discussion can foster the development of analytical skills pertaining to sound analysis.
Three-dimensional tuning of idiophone bar modes via finite element analysis
Authors: Beaton Douglas , Scavone Gary
Published: June 2021

The timbre of marimba and other idiophone bars can sometimes be polluted by untuned torsional modes, leading to substandard instruments or rejected materials. Makers have complained of problems with these untuned modes over a specific range of notes. Marimba, vibraphone, and similar idiophone bars are tuned by carving one side of the bar to bring up to three flexural modes into harmonic relationships. Torsional and other mode types are commonly left untuned. The relative frequency of these untuned modes with respect to the fundamental mode will vary along the keyboard. This paper investigates tuning both torsional and flexural modes simultaneously. This tuning is achieved using sophisticated carved geometries, and without employing concentrated masses or additional materials. Bars are modeled using three-dimensional finite elements. Geometry is defined by a large number of input parameters. Algorithms are implemented to identify bar modes automatically, eliminating the need for human intervention. Tuning is performed via a Newton-Raphson approach using the Moore-Penrose generalized matrix inverse to solve systems of tuning equations. This method is found to be effective at finding satisfactory bar geometries in proximity to initial conditions. Numerous example marimba and vibraphone bar models are provided, representing both typical and atypical modal tuning ratios.
An overview of seabed characterization experiment
Authors: Wilson Preston S. , Knobles David P.
Published: June 2021

An overview of the Spring 2021 component of the Seabed Characterization Experiment will be presented. The project is focused on the acoustics of fine-grained ocean bottom sediments. The study site is the New England Shelf, south of Martha’s Vineyard, MA, USA. The goals of the project are (1) understand the physical mechanisms that control acoustic propagation in fine-grained sediments, (2) quantify uncertainties in the estimation of seabed parameters, (3) correlate the observed horizontal variations in the acoustical field with the measured horizontal variability of the seabed and (4) assess the performance of the resulting geoacoustic models, and inversion and statistical inference methods. These goals have been pursued by obtaining direct measurements and/or inferring the values of the following parameters over a wide frequency band: compressional wave speed and attenuation, shear wave speed and attenuation, and seabed layering and gradients. Oceanographic data were collected to support both forward and inverse modeling efforts. A major part of this effort was completed in 2017 and a follow-on effort is planned for 2021 and 2022. This presentation provides an overview of the project, a summary of past results, and a discussion of the most recent work. [Work supported by ONR.]
Strongly enhanced and tunable photovoltaic effect in ferroelectric-paraelectric superlattices
Authors: Yun Yeseul , Mühlenbein Lutz , Knoche David S. , Lotnyk Andriy , Bhatnagar Akash
Published: June 2021

Sandwiching a ferroelectric between two paraelectrics squeezes out larger photovoltaic current.
Ultrafast self-gelling powder mediates robust wet adhesion to promote healing of gastrointestinal perforations
Authors: Peng Xin , Xia Xianfeng , Xu Xiayi , Yang Xuefeng , Yang Boguang , Zhao Pengchao , Yuan Weihao , Chiu Philip Wai Yan , Bian Liming
Published: June 2021

Ultrafast self-gelling polymeric powder with strong wet bioadhesion can be used as effective tissue sealant.
Anion ordering enables fast H
−
conduction at low temperatures
Authors: Ubukata Hiroki , Takeiri Fumitaka , Shitara Kazuki , Tassel Cédric , Saito Takashi , Kamiyama Takashi , Broux Thibault , Kuwabara Akihide , Kobayashi Genki , Kageyama Hiroshi
Published: June 2021

Layered anion order in Ba
2
H
3
X
(
X
= halogen) stabilizes its high-symmetry structure, enabling excellent H
−
conduction below 300°C.
Renatured hydrogel painting
Authors: Yang Zhaoxiang , He Yonglin , Liao Shenglong , Ma Yingchao , Tao Xinglei , Wang Yapei
Published: June 2021

A scalable hydrogel painting method based on hydrogel renaturation can firmly adhere hydrogel to diverse solid surfaces.
The development of a functional human small intestinal epithelium model for drug absorption
Authors: Kwon Ohman , Jung Kwang Bo , Lee Kyeong-Ryoon , Son Ye Seul , Lee Hana , Kim Jong-Jin , Kim Kwangho , Lee Seop , Song Yoo-Kyung , Jung Jaeeun , Park Kunhyang , Kim Dae-Soo , Son Myung Jin , Lee Mi-Ok , Han Tae-Su , Cho Hyun-Soo , Oh Soo Jin , Chung Haeun , Kim Sang-Heon , Chung Kyung-Sook , Kim Janghwan , Jung Cho-Rok , Son Mi-Young
Published: June 2021

Directed differentiation of hPSCs and transition from 3D intestinal organoids into functional hIECs.
Emulsan production by Acinetobacter calcoaceticus in the presence of chloramphenicol
Authors: Rubinovitz C , Gutnick D L , Rosenberg E
Published: June 2021

When exponentially growing cultures of Acinetobacter calcoaceticus RAG-1 or RAG-92 were either treated with inhibitors of protein synthesis or starved for a required amino acid, there was a stimulation in the production of emulsan, an extracellular polyanionic emulsifier. Emulsan synthesis in the presence of chloramphenicol was dependent on utilizable sources of carbon and nitrogen and was inhibited by cyanide or azide or anaerobic conditions. Radioactive tracer experiments indicated that the enhanced production of emulsan after the addition of chloramphenicol was due to both the release of material synthesized before the addition of the antibiotic (40%) and de novo synthesis of the polymer (60%). Chemical analysis of RAG-1 cells demonstrated large amounts of polymeric amino sugars; it was estimated that cell-associated emulsan comprised about 15% of the dry weight of growing cells. The data are consistent with the hypothesis that a polymeric precursor of emulsan accumulates on the cell surface during the exponential growth phase; in the stationary phase or during inhibition of protein synthesis, the polymer is released as a potent emulsifier.
Anaerobic incubation enhances the colony formation of a polA recB strain of Escherichia coli K-12
Authors: Morimyo M
Published: June 2021

Escherichia coli strain E247 (polA1 recB21) has reduced colony formation (even at the permissive temperature of 30 degrees C) because of a poor suppressor mutation (sup-126). The colony formation was enhanced in the absence of oxygen about 3-fold at 30 degrees C and 10(6)-fold at 43 degrees C, suggesting that a polA recB strain was inviable due to oxygen toxicity. Colony formation was also increased by incubation in an agar medium containing the reducing agent thioglycolate and incubation in the presence of chloroform-killed Saccharomyces cerevisiae pet+ cells, but not pet cells. Since the E247 strain viability was inversely dependent on the oxygen pressure and since the strain was more sensitive to superoxide radical than either the polA or the recB mutant, it seems likely that the polA and recB genes play a role in repairing DNA damage during respiration.
Evidence for a messenger function of cyclic GMP during phosphodiesterase induction in Dictyostelium discoideum
Authors: van Haastert P J , Pasveer F J , van der Meer R C , van der Heijden P R , van Walsum H , Konijn T M
Published: June 2021

Chemotactic stimulation of vegetative or aggregative Dictyostelium discoideum cells induced a transient elevation of cyclic GMP levels. The addition of chemoattractants to postvegetative cells by pulsing induced phosphodiesterase activity. The following lines of evidence suggest a messenger function for cyclic GMP in the induction of phosphodiesterase: (i) Folic acid and cyclic AMP increased cyclic GMP levels and induced phosphodiesterase activity. (ii) Cyclic AMP induced both cyclic GMP accumulation and phosphodiesterase activity by binding to a rate receptor. (iii) The effects of chemical modification of cyclic AMP or folic acid on cyclic GMP accumulation and phosphodiesterase induction were closely correlated. (iv) A close correlation existed between the increase of cyclic GMP levels and the amount of phosphodiesterase induced, independent of the type of chemoattractant by which this cyclic GMP accumulation was produced. (v) Computer simulation of cyclic GMP binding to intracellular cyclic GMP-binding proteins indicates that half-maximal occupation by cyclic GMP required the same chemoattractant concentration as did half-maximal phosphodiesterase induction.
Polyamine-deficient Neurospora crassa mutants and synthesis of cadaverine
Authors: Paulus T J , Kiyono P , Davis R H
Published: June 2021

The polyamine path of Neurospora crassa originates with the decarboxylation of ornithine to form putrescine (1,4-diaminobutane). Putrescine acquires one or two aminopropyl groups to form spermidine or spermine, respectively. We isolated an ornithine decarboxylase-deficient mutant and showed the mutation to be allelic with two previously isolated polyamine-requiring mutants. We here name the locus spe-1. The three spe-1 mutants form little or no polyamines and grow well on medium supplemented with putrescine, spermidine, or spermine. Cadaverine (1,5-diaminopentane), a putrescine analog, supports very slow growth of spe-1 mutants. An arginase-deficient mutant (aga) can be deprived of ornithine by growth in the presence of arginine, because arginine feedback inhibits ornithine synthesis. Like spe-1 cultures, the ornithine-deprived aga culture failed to make the normal polyamines. However, unlike spe-1 cultures, it had highly derepressed ornithine decarboxylase activity and contained cadaverine and aminopropylcadaverine (a spermidine analog), especially when lysine was added to cells. Moreover, the ornithine-deprived aga culture was capable of indefinite growth. It is likely that the continued growth is due to the presence of cadaverine and its derivatives and that ornithine decarboxylase is responsible for cadaverine synthesis from lysine. In keeping with this, an inefficient lysine decarboxylase activity (Km greater than 20 mM) was detectable in N. crassa. It varied in constant ratio with ornithine decarboxylase activity and was wholly absent in the spe-1 mutants.
Aerobic and anaerobic respiratory systems in Campylobacter fetus subsp. jejuni grown in atmospheres containing hydrogen
Authors: Carlone G M , Lascelles J
Published: June 2021

Maximum growth of Campylobacter fetus subsp. jejuni, strain C-61, occurred when the cultures were incubated with shaking in atmospheres containing approximately 30% hydrogen, 5% oxygen, and 10% CO2. Suspensions of cells grown under these conditions consumed oxygen with formate as the substrate in the presence of 0.33 mM cyanide, which completely inhibited respiration with ascorbate-N,N,N',N'-tetramethyl-p-phenylenediamine and with lactate. Spectroscopic evidence with intact cells suggested that a form of cytochrome c, reducible with formate but not with lactate or ascorbate-N,N,N',N'-tetramethyl-p-phenylenediamine, can be reoxidized by a cyanide-insensitive system. Analysis of membranes from the cells showed high- and low-potential forms of cytochrome c, cytochrome b, and various enzymes, including hydrogenase, formate dehydrogenase, and fumarate reductase. The predominant carbon monoxide-binding pigment appeared to be a form of cytochrome c, but the spectra also showed evidence of cytochrome o. The membrane cytochromes were reduced by hydrogen in the presence of 2-heptyl-4-hydroxyquinoline-N-oxide at concentrations which prevented the reduction of cytochrome c with succinate as the electron donor. Reoxidation of the substrate-reduced cytochromes by oxygen was apparently mediated by cyanide-sensitive and cyanide-insensitive systems. The membranes also had hydrogen-fumarate oxidoreductase activity mediated by cytochrome b. We conclude that C. fetus jejuni has high- and low-potential forms of cytochrome which are associated with a complex terminal oxidase system.
Action of restriction endonucleases on transforming DNA of Haemophilus influenzae
Authors: Beattie K L , Wakil A E , Driggers P H
Published: June 2021

Cleavage of DNA from Haemophilus influenzae with restriction endonucleases caused inactivation of transforming ability to an extent that depended on the genetic marker and the enzyme. The rate of inactivation, but not the final level of survival, depended on the concentration of enzyme in the restriction digest. In general, the greatest extent of inactivation of transforming activity was obtained with endonucleases that are known to produce the shortest fragments. We electrophoresed restriction digests of H. influenzae DNA in agarose gels and assayed transforming activity of DNA extracted from gel slices. In this way, we determined the lengths of restriction fragments that contain genetic markers of H. influenzae. For the marker that we studied most thoroughly (nov), the shortest restriction fragment that possessed detectable transforming activity was a 0.9-kilobase pair fragment produced by endonuclease R . PstI. The shortest marker-bearing restriction fragment that retained substantial transforming activity (50% of value for undigested DNA) was a 2.1-kilobase pair EcoRI fragment bearing the kan marker. Among marker-bearing restriction fragments 1 to 4 kilobase pairs in length, survival of transforming activity varied 10,000-fold. We relate these observations to the recent findings by Sisco and Smith (Proc. Natl. Acad. Sci. U.S.A. 76:972-976, 1979) that efficient entry of DNA into competent H. influenzae cells appears to require the presence of a recognition sequence that is scattered throughout the Haemophilus genome in many more copies than in unrelated genomes.
Attenuation regulation in the thr operon of Escherichia coli K-12: molecular cloning and transcription of the controlling region
Authors: Lynn S P , Gardner J F , Reznikoff W S
Published: June 2021

Recombinant plasmids were constructed which carry defined regions of the threonine (thr) operon regulatory region of Escherichia coli. In vitro transcription experiments utilizing plasmid or restriction fragment templates showed that two major RNA transcripts, which differ in length by one to a few bases, are transcribed from this region. The approximate length of the transcripts is 150 to 170 bases, and the site(s) of termination is near or within the thr attenuator. The efficiency of termination at the thr operon attenuator in vitro is approximately 90%. A regulatory mutation, thr79-20, which is a G-C insertion in the attenuator, reduces the frequency of transcription termination to 75%. In addition, in vivo RNA transcripts were identified which hybridize to the thr operon regulatory region. These transcripts appeared to be identical to the two major in vitro transcripts as judged by their mobilities on 8% polyacrylamide-8 M urea gels. This result indicates that the thr operon regulatory region is transcribed in vivo and that termination occurs near or within the thr attenuator.
Effects of pH and Repellent Tactic Stimuli on Protein Methylation Levels in
Escherichia coli
Authors: Slonczewski Joan L. , Macnab Robert M. , Alger Jeffry R. , Castle Anna M.
Published: June 2021

Intracellular pH (pH
int
) and extracellular pH (pH
ext
) of
Escherichia coli
were measured at 12-s time resolution by
31
P-nuclear magnetic resonance: a sudden neutral-to-acid shift in pH
ext
(e.g., from 7.0 to 5.6) caused a transient failure of homeostasis, with pH
int
decreasing by about 0.4 unit in ca. 30 s and then returning to its original value (ca. 7.5) over a period of several minutes. Membrane proton conductance was estimated to be 20 pmol s
−1
cm
−2
pH unit
−1
. Addition of the membrane-permeant weak acid benzoate at constant pH
ext
also caused a lowering of pH
int
; at high concentrations it generated an inverted transmembrane pH gradient (ΔpH). The buffering capacity of the cells was estimated by such experiments to be ca. 50 mM per pH unit. Effects of pH-related stimuli on the methyl-accepting chemotaxis proteins (MCPs) were examined: the steady-state methylation of MCP I was found to decrease when pH
int
was lowered by weak acid addition or when pH
ext
was lowered. The extent of demethylation in the latter case was too great to be explained by imperfect steady-state homeostasis; a small but reproducible undershoot in methylation level correlated with the observed short-term homeostatic failure. MCP II underwent smaller and more complex changes than MCP I, in response to pH-related stimuli. The methylation level of MCP I could not, by any condition tested, be driven below a limit of ca. 15% of the control level (unstimulated cells at pH
ext
7.0). The weak-acid concentration needed to reach that limit was dependent on pH
ext
, as would be expected on the basis of ΔpH-driven concentrative effects. The potency ranking of weak acids was the same with respect to lowering pH
int
, demethylating MCP I, and causing repellent behavioral responses. The data are consistent with a model whereby MCP I and hence tactic behavior are sensitive to both pH
int
and pH
ext
. Evidence is presented that pH
int
may also have a direct (non-MCP-related) effect on motor function. Comparison of
methyl
-
3
H- and
35
S-labeled MCP I revealed that in both unstimulated and repellent-stimulated cells the major species did not carry methyl label, yet it had an electrophoretic mobility that indicated that it was more positively charged than the unmethylated form observed in methyltransferase mutants, and it was susceptible to base hydrolysis. This suggests that a substantial fraction of MCP I molecules is methylated or otherwise modified but neither exchanges methyl label nor undergoes reverse modification by repellent stimuli.
Murein components rescue developmental sporulation of Myxococcus xanthus
Authors: Shimkets L J , Kaiser D
Published: June 2021

Murein (peptidoglycan) components are able to rescue sporulation in certain sporulation-defective mutants of Myxococcus xanthus. N-Acetylglucosamine, N-acetylmuramic acid, diaminopimelic acid, and D-alanine each increase the number of spores produced by SpoC mutants. When all four components are included they have a synergistic effect, raising the number of spores produced by SpoC mutants to the wild-type level. Murein-rescued spores are resistant to heat and sonic oscillation and germinate when plated on a nutrient-rich medium. They appear to be identical to fruiting body spores in their ultrastructure, in their protein composition, and in their resistance to boiling sodium dodecyl sulfate. Murein rescue of sporulation, like fruiting body sporulation, requires high cell density, a low nutrient level, and a solid surface.
Physiological Adaptation to the Loss of Amino Acid Transport Ability
Authors: DeBusk Ruth M. , Ogilvie-Villa Susan
Published: June 2021

A strain of
Neurospora crassa
devoid of constitutive amino acid transport ability can utilize arginine as the sole nitrogen source. Nitrogen starvation, presence of arginine, and mutational inactivation of the general permease are key factors in signaling production of an extracellular enzyme which removes the alpha-amino group from the amino acid.
Genetic and physical map of a P1 miniplasmid
Authors: Austin S , Hart F , Abeles A , Sternberg N
Published: June 2021

The prophage form of bacteriophage P1 is a unit-copy plasmid which is maintained with great fidelity in its Escherichia coli host. The plasmid maintenance functions of P1 are clustered in one region of the genome. An 11.5-kilobase fragment from this region has been cloned into a lambda delta att vector and promotes stable unit-copy plasmid maintenance. The properties of the lambda vector facilitated the isolation of deletion mutants affecting the P1 DNA. Twenty-eight deletion mutants were isolated, and their lesions were mapped by physical techniques. The genetic properties of the mutants with respect to plasmid replication, stability of plasmid maintenance, and ability to exert incompatibility effects against P1 and P7 plasmids were determined. These properties, along with those of several subfragments of the P1 insert cloned into high-copy-number plasmid vectors, allow the construction of an unambiguous genetic and physical map of the maintenance functions. A region of less than 3 kilobases, the rep region, is essential for plasmid replication and contains the incA incompatibility determinant within an 800-base-pair segment. Immediately adjacent to rep is a second region of approximately 3 kilobases which is required for stable plasmid maintenance, but not replication. This region, par, contains a second incompatibility element incB which is approximately 1 kilobase in size. The par region appears to specify equipartition of plasmid copies to daughter cells during cell division.
Escherichia coli phenylalanyl-tRNA synthetase operon: characterization of mutations isolated on multicopy plasmids
Authors: Plumbridge J A , Springer M
Published: June 2021

Plasmid pB1 carries the genes for threonyl-tRNA synthetase, phenylalanyl-tRNA synthetase, and translation initiation factor IF3. Strains carrying this plasmid overproduce phenylalanyl-tRNA synthetase about 100-fold. Spontaneous mutant plasmids were obtained which no longer caused the overproduction of the enzyme. Three classes of mutations were found. (i) Deletion mutations were found, some of which had the interesting property of fusing different genes together, e.g., putting phenylalanyl-tRNA synthetase under the control of the threonyl-tRNA synthetase promoter. (ii) Insertion mutations were found; one insertion in particular was studied. This insertion is located in front of the structural gene for phenylalanyl-tRNA synthetase and is shown to interrupt a cis-acting regulatory region. (iii) Mutations that showed no major change in DNA structure were found. One of these mutations is apparently purely structural, as it produces a small subunit of phenylalanyl-tRNA synthetase with a reduced molecular weight. This protein is less stable than the wild-type enzyme. These mutations represent useful tools to investigate how the phenylalanyl-tRNA synthetase operon is regulated.
Electrochemical proton gradient and lactate concentration gradient in Streptococcus cremoris cells grown in batch culture
Authors: ten Brink B , Konings W N
Published: June 2021

The lactate concentration gradient and the components of the electrochemical proton gradient (delta micro H+) were determined in cells of Streptococcus cremoris growing in batch culture. The membrane potential (delta psi) and the pH gradient (delta pH) were determined from the accumulation of the lipophilic cation tetraphenylphosphonium and the weak acid benzoate, respectively. During growth the external pH decreased from 6.8 to 5.3 due to the production of lactate. Delta pH increased from 0 to -35 mV, inside alkaline (at an external pH of 5.7), and fell to zero directly after growth stopped. Delta psi was nearly constant at -90 mV during growth and also dissipated within 40 min after termination of growth. The internal lactate concentration decreased from 200 mM at the beginning of growth (at pH 6.8) to 30 mM at the end of growth (at pH 5.3); the external lactate concentration increased from 8 to 30 mM due to the fermentation of lactose. Thus, the lactate gradient decreased from 80 mV to zero as growth proceeded and the external pH decreased. From the data obtained on delta psi, delta pH, and the lactate concentration gradient, the H+/lactate stoichiometry (n) was calculated. The value of n varied with the external pH from 1.9 (at pH 6.8) to 0.9 (at pH values below 6). This implies that especially at high pH values the carrier-mediated efflux of lactate supplies a significant quantity of metabolic energy to S. cremoris cells. At pH 6.8 this energy gain was almost two ATP equivalents per molecule of lactose consumed if the H+/ATP stoichiometry equals 2. These results supply strong experimental evidence for the energy recycling model postulated by Michels et al.