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Multiple sclerosis (MS) is an inflammatory, autoimmune demyelinating disorder of the central nervous system (CNS), leading to progressive functional impairments, and many intrinsic and acquired factors are believed to be associated with its development and relapse. In terms of environmental factors, air pollution has gained much attention during recent decades, as chronic exposure to ambient air pollution seems to increase the level of some pro-inflammatory markers in the human brain, which can lead to neuroinflammation, neurodegeneration, and blood-brain barrier (BBB) breakdown. These events may also be associated with the risk of MS development and relapse. In this review, we aimed to summarize recent findings around the impact of air pollutants, including particulate matter (PM10, PM2.5, and ultra-fine particles), gaseous pollutants (carbon monoxide [CO], nitrogen oxides [NOx], sulfur dioxide [SO2], and ozone [O3]), and heavy metals, on MS development and relapse.

Coronavirus disease 2019 (COVID-19) pandemic has struck many countries and caused a great number of infected cases and death. Healthcare system across all countries is dealing with the increasing medical, social, and legal issues caused by the COVID-19 pandemic, and the standards of care are being altered. Admittedly, neurology units have been influenced greatly since the first days, as aggressive policies adopted by many hospitals caused eventual shut down of numerous neurologic wards. Considering these drastic alterations, traditional ethical principles have to be integrated with state-of-the-art ethical considerations. This review will consider different ethical aspects of care in neurologic patients during COVID-19 and how this challenging situation has affected standards of care in these patients.

Osteoma cutis (OC) or cutaneous ossification refers to uncommon bone formation in the skin. Primary OC develops without any predisposing factor or pre-existing lesion, whereas secondary OC sets out as a dystrophic ossification following traumatic, cicatricial, and neoplastic factors or other cutaneous inflammations. Herein, we report a rare case of long-standing progressive primary OC of the scalp resected in 3 sessions with no recurrence after 1 year.

Aims Cardiovascular diseases (CVDs) are the leading cause of death in the world. Many modifiable risk factors have been reported to synergistically act in the development of CVDs. We aimed to compare the predictive power of anthropometric indices, as well as to provide the best cut-off point for these indicators in a large population of Iranian people for the prediction of CVDs and CVD risk factors. Methods and results All the data used in the present study were obtained from Khuzestan comprehensive health study (KCHS). Anthropometric indices, including BMI (body mass index), WC (waist circumference), HC (hip circumference), WHR (waist-to-hip ratio), WHtR (waist-to-height ratio), ABSI (a body shape index), as well as CVD risk factors [dyslipidaemia, abnormal blood pressure (BP), and hyperglycaemia] were recorded among 30 429 participants. WHtR had the highest adjusted odds ratios amongst anthropometric indices for all the risk factors and CVDs. WC had the highest predictive power for dyslipidaemia and hyperglycaemia [area under the curve (AUC) = 0.622, 0.563; specificity 61%, 59%; sensitivity 69%, 60%; cut-off point 87.95, 92.95 cm, respectively], while WHtR had the highest discriminatory power for abnormal BP (AUC = 0.585; specificity 60%; sensitivity 65%; cut-off point 0.575) and WHR tended to be the best predictor of CVDs (AUC = 0.527; specificity 58%; sensitivity 64%; cut-off point 0.915). Conclusion In this study, we depicted a picture of the Iranian population in terms of anthropometric measurement and its association with CVD risk factors and CVDs. Different anthropometric indices showed different predictive power for CVD risk factors in the Iranian population.

Background. Coronavirus disease 2019 (COVID-19) was initially detected in Wuhan city, China. Chest CT features of COVID-19 pneumonia have been investigated mostly in China, and there is very little information available on the radiological findings occurring in other populations. In this study, we aimed to describe the characteristics of chest CT findings in confirmed cases of COVID-19 pneumonia in an Iranian population, based on a time classification. Methods. Eighty-nine patients with COVID-19 pneumonia, confirmed by a real-time RT-PCR test, who were admitted to non-ICU wards and underwent a chest CT scan were retrospectively enrolled. Descriptive evaluation of radiologic findings was performed using a classification based on the time interval between the initiation of the symptoms and chest CT-scan. Results. The median age of patients was 58.0 years, and the median time interval from the onset of symptoms to CT scan evaluation was 7 days. Most patients had bilateral (94.4%) and multifocal (91.0%) lung involvement with peripheral distribution (60.7%). Also, most patients showed involvement of all five lobes (77.5%). Ground-glass opacities (GGO) (84.3%) and mixed GGO with consolidation (80.9%) were the most common identified patterns. We also found that as the time interval between symptoms and CT scan evaluation increased, the predominant pattern changed from GGO to mixed pattern and then to elongated-containing and band-like-opacities-containing pattern; on the other hand, the percentage of lung involvement increased. Conclusions. Bilateral multifocal GGO, and mixed GGO with consolidation were the most common patterns of COVID-19 pneumonia in our study. However, these patterns might change according to the time interval from symptoms.

Necrobiosis lipoidica‐like lesions, in known cases of sarcoidosis, can be considered as a member of the broad spectrum of histologic changes in sarcoidosis.

BACKGROUND Breast cancer, with an incidence of 33.2 per 100,000 in Iranian population, is considered as the most common cancer in Iranian women. Nowadays, with the increasing survival rates, breast reconstruction has been integrated into surgical techniques of breast cancer treatment. The aim of this study was to evaluate the current status of breast reconstruction in Iranian population. PATIENTS AND METHODS This retrospective study was conducted in Imam Hospital between January 2008 and June 2018. All the patients underwent breast reconstruction surgery. The trend of reconstruction and complication rates were 2 major outcomes. Logistic regression model was used to predict complications. Student t test was used to compare means. RESULTS Fifty-five patients underwent 60 autologous breast reconstruction surgeries and 152 patients underwent 193 prosthesis-based reconstruction surgeries. Most of cases were invasive ductal carcinoma ± ductal carcinoma in situ (126 cases, 68%). Among 253 surgeries in 207 patients, 98 cases (38.7%) were 2-stage implant, 91 (36.0%) were 1-stage implant, 3 (1.2%) were acellular dermal matrix + prosthesis, 31 (12.2%) were pedicled transverse rectus abdominis myocutaneous flap, 25 (9.8%) were latissimus dorsi flap ± prosthesis, and 4 (15.8%) were latissimus dorsi flap. Among prosthesis-based reconstructions, chemotherapy could predict the occurrence of complications (odds ratio, 2.87; 95% CI, 1.07-7.68), whereas none of these factors could predict the occurrence of complications in autologous reconstructions. The most prevalent complication was seroma formation (48.5% of all complications). Overall complication rates (including major and minor) were higher among autologous reconstructions compared with prosthesis-based reconstructions (45.8% and 21.1%, respectively, P < 0.001). CONCLUSIONS The trend of breast reconstruction is changing in Islamic Republic of Iran as a developing country. Implant-based reconstruction has surpassed autologous reconstructions in recent years. In terms of complications, we observed higher rates among autologous reconstructions.

First presentation of the Kaposi sarcoma (KS) on the penis is not prevalent, and it was reported in 2%‐3% of the cases that mostly occurred in the HIV‐positive patients. Here, we report a case of primary KS on the glans penis in an HIV‐negative patient.

Background Magnetic resonance imaging (MRI) is a non-invasive highly sensitive tool for diagnosing chondromalacia patellae in the early stages. Many studies have evaluated patellar and trochlear morphology with different radiologic indices. We aimed to assess the discriminative power of tibial, patellar, and femoral indices in MRI for chondromalacia patellae. Patients and methods 100 cases of chondromalacia, as well as 100 age-matched controls among the patients who underwent knee MRI between February 2017 and March 2019, were included. The standard protocol of knee MRI was applied and the diagnosis of chondromalacia was made on MRI findings. Chondromalacia subjects were also classified as grade 1 to 4 according to the Modified Outerbridge’s MRI grading system. We measured 25 MRI parameters in the knee and adjacent structures to determine the relation between chondromalacia patellae and anatomical MRI parameters. Results Tibial slope, trochlear depth, lateral trochlear inclination, and lateral patellar tilt angle had significant correlation with chondromalacia. Any increase in lateral trochlear inclination and lateral patellar tilt angle could increase the probability of the disease (Odds ratio [OR] 1.15, 1.13; 95% CI: 1.03–1.30; 1.02–1.26, respectively), while any increase in medial tibial slope and trochlear depth could decrease the probability of chondromalacia (OR 0.85, 0.06; 95% CI: 0.73–0.98, 0.02–0.17, respectively). We also designed a model for the severity of disease by using the patellar height index (relative odds ratio: 75.9). Conclusions The result of this study showed the novelty role of tibial anatomy in developing chondromalacia and its mechanism. We also concluded that patellar height might be an important factor in defining disease severity.

Metastasis of head and neck squamous cell carcinoma (SCC) to the skin of this region is extremely rare and reported in 1-2% of cases. The cutaneous metastases of head and neck cancers often present as multiple papulonodular lesions; however, sporadic cases of solitary or multiple keratoacanthoma-like lesions are reported. We describe a rare case of cutaneous metastases of laryngeal SCC presenting as multiple eruptive keratoacanthoma-like lesions with concomitant scrofuloderma in an area of previous radiotherapy.

Pemphigus vulgaris is a potential life-threatening autoimmune bullous disorder. The significant role of autoreactive B cells in the pathogenesis of PV has been explained extensively by producing autoantibodies. Recently, attention has been directed toward the role of T cells in the pathogenesis of PV; in other words, the underlying etiology of PV depends on the interaction between T cells and B cells resulting in antibody secretion. Herein, we systematically review the current literature on the emerging role of T cells in PV. To perform this systematic review, an extensive search through EMBASE, PubMed, Scopus, and ISI databases was performed from 1976 through 2021. Articles investigating the function of T cell subgroups in the pathogenesis or treatment of pemphigus vulgaris were included and reviewed. It is evidenced that T cells play a pivotal role in PV pathogenesis. Th1 and Th2 dichotomy including Th1 suppression and Th2 elevation may induce antibody production against desmoglein in keratinocytes. Furthermore, increased level of Th17 and decreased level of regulatory T cells have been detected in PV patients. However, further studies on the exact role of γδ-T cells in PV are required in order to clarify the pathogenesis of PV. T cells and their subtypes can be involved in the pathogenesis of PV. Thus, they can be considered as tentative targets of novel therapies for PV.

We report two cases of lichen planus following COVID-19 vaccination in two middle-aged women, where the first patient presented with lichenplanopilaris (LPP) relapse and development of lichen planus 14 days after the second dose of AstraZeneca vaccine, and the other patient who had a previous scattered lesion of LP which extended and increased in severity after the first and second dose of Sinopharm. The suggested cause could be due to immune dysregulation and up regulation of T cell lymphocytes which was triggered after COVID-19 vaccination. What supports our hypothesis that LP had occurred due to COVID-19 vaccination, is that one of the patients responded successfully to Metronidazole. This means that the infection process after vaccination could be the cause in aggravating LP. To add, one of the suggested mechanisms for the appearance of LP or reactivation of a dormant LPP can be cytotoxic CD8 T-lymphocytes which increase the secretion of IFN-γ and IL-5 cytokines and may also result in basal keratinocytes' apoptosis leading to cutaneous manifestations. This was supported by the efficacy of Tofacitinib that was used in the other patient who presented with reactivation of LPP in addition to LP. Tofacitinib decrease the number of T cell infiltration and adjust IFN expression.

The novel coronavirus disease 2019 (COVID-19), caused by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), was announced as a pandemic in March 2020. Different diagnostic laboratory tests have been used to detect the infection. Each diagnostic tool, such as Chest Computed tomography (CT) imaging, genome sequencing, nucleic acid amplification methods, whole genome sequencing, microarray, and serology testing have several advantages and disadvantages. Nucleic acid amplification methods are better diagnostic tools for the detection of SARS-CoV-2 in early stages of the infection, while serological tests are more appropriate for the recognition of previously infected patients. In this review, we will briefly consider each diagnostic method, and discuss its pros and cons.

Treatment of pigmented lesions is one of the major challenges of laser and cosmetic practitioners. The most common pigmented lesions that are treated by lasers are melanocytic nevi, ephelides, solar lentigines, and café au lait macules. Melanin absorbs different wavelengths (500-1100 nm); thereby, treatment of various pigmented lesions requires the application of lasers with different wavelengths. Choosing the most appropriate type of laser depends on various factors such as the chromophore and the location of a specific lesion in the skin. In this paper, we aim to review the most efficient laser treatment protocols for each pigmented skin lesion and compare their efficacy in each part based on the previous studies.

Nodular or keloidal morphea, also known as nodular scleroderma, is a rare form of localized sclerosis (SSc) or morphea. In this paper, we reported a case of this rare entity with a review of the literature.

Pemphigus vulgaris which is an autoimmune dermatological disorder characterized by vesiculobullous lesions over the skin and mucosae may also give rise to cardiac disease. Global Longitudinal Strain (GLS) measurement may help to predict cardiac dysfunction in these patients.In this prospective study, the GLS was measured before and after steroid pulse therapy in pemphigus vulgaris patients using 2 D speckle-tracking echocardiography. Moreover, blood pressure, pulse rate, and corrected QT (cQT) interval were recorded before and after steroid pulse therapy.We included 23 pemphigus patients. The mean age of patients was 34.5(±6.4). Mean GLS decreased significantly after the administration of steroid pulse therapy. The mean GLS decreased regardless of age, however, the patients with the age range of 40-50 years showed the highest change in GLS. There was no interaction between gender and GLS change. Mean cQT increased significantly after pulse therapy (The steroid pulse therapy may associate with the progression of cardiac dysfunction in pemphigus patients. GLS, as a predictor, may be a valuable marker of cardiac subclinical dysfunction in this condition.

Effects of variable dust size, mass and charge on the characteristics of nonlinear dust acoustic solitary waves (DASW) in a two-temperature ion dusty plasma have been studied analytically. Plasma ions are assumed to be Maxwellian while plasma electrons are nonextensively distributed. Mass and electrical charge of dust particles are assumed to be proportional to their size. Plasma is embedded in an external magnetic field with variable direction. The Zakharov–Kuznetsov equation was derived using reductive perturbation method, and its solitary answers were extracted. Dispersion relation of DASW shows that this wave may generate in plasma only if the nonextensivity coefficient, q, is positive. For all allowed magnitudes of c (the ratio of the largest dust radius to smallest dust radius) and q, only rarefactive solitons may be formed in plasma. Effect of variable dust size on the width and amplitude of DASW is noticeable when c is smaller than 3. Both the width and amplitude of DASW increase with increasing c, and with increasing the nonextensivity of plasma, effect of variable size increases. Results show that increasing the strength of external magnetic field leads to localization of DASW while both the width and amplitude of DASW are under the influence of the direction of the external magnetic field simultaneously.

Background Oncoplastic breast surgery (OBS) is becoming an acceptable procedure for the surgical treatment of breast cancer; however, its safety and recurrence rate still need further clarification. This study evaluates the rate of local recurrence and its predictive factors after OBS in a large series of patients. Materials and methods This study was conducted between January 2008 and June 2018 in two centers in Iran. Patients underwent OBS, and baseline characteristics were recorded. Patients underwent regular follow-up; local recurrence rate, median time, and the hazard ratio of predictive factors were calculated. Also, a multivariate analysis was performed. Results A total of 676 patients with a mean age of 48 ± 10.7 y were included. The median follow-up time was 26.4 (first, third IQR: 13.2, 45.6) mo, and 37 (5.5%) patients were diagnosed with local recurrence. The median time to local recurrence was 22.0 (first, third IQR: 16.0, 32.8) mo. Pathological N stage, neoadjuvant chemotherapy, overexpression of HER2, and one surgery technique was associated with a higher risk of recurrence, while the expression of estrogen receptor and progesterone receptor (PR) decreased the risk of recurrence. PR status, neoadjuvant chemotherapy, and pathological N stage remained significant in the final model for recurrence on multivariate analysis. Conclusion OBS is a safe technique with an acceptable risk of local recurrence. PR status, neoadjuvant chemotherapy, and pathological N stage can predict recurrence in these patients with an acceptable power.

Background: In this study, we assessed the prevalence of positive rapid detection test (RDT) among healthcare workers (HCWs) and evaluated the role of personal protective equipment (PPE) and knowledge of the pandemic. Methods: In a cross-sectional study conducted between August 2020 and October 2020 in a tertiary referral center (Tehran, Iran), we enrolled 117 physicians, nurses, and other HCWs (OHCWs)—aides, helpers, and medical waste handlers—regularly working in coronavirus disease 2019 (COVID-19) wards. The RDT kit was utilized to reveal recent infection; data on demographics, PPE use and availability, and knowledge of the pandemic was collected through pre-defined questionnaires. Results: Overall, 24.8% (95% CI: 16.8–32.7%) of HCWs had positive RDTs. The more PPE was available and used, the less the chance of positive RDT was (OR: 0.63 [0.44–0.91], P = 0.014 and 0.63 [0.41–0.96], P = 0.030). The same was true for the knowledge of prevention and adhering to preventive rules (OR: 0.44 [0.24–0.81], P = 0.008 and 0.47 [0.25–0.89], P = 0.020). OHCWs had the highest prevalence of positive RDT, while they had more shifts per month, less accessibility to PPE, and less knowledge of the pandemic than physicians. Conclusion: The findings of this study suggest that HCWs should have a thorough knowledge of the pandemic along with using PPE properly and rationally. Furthermore, adhering to preventive regulations plays a crucial role in HCWs’ safety. It is also noteworthy that shifts should be arranged logically to manage exposures, with a special attention being paid to OHCWs.

As the largest organ in the body, human skin is constantly exposed to harmful compounds existing in the surrounding environment as the first-line barrier. Studies have indicated that exposure to high concentrations of many environmental factors, such as ultraviolet (UV) radiation, outdoor air pollutants, including polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), particulate matter (PM), heavy metals, gaseous pollutants, such as carbon monoxide (CO), nitric oxides (NOx ), sulfur oxide (SO2 ), ozone (O3 ), and indoor air pollutants (solid fuels consumption), might interrupt the skin's normal barrier function. Besides, the intensity of the pollutants and the length of exposure might be a contributing factor. Air pollutants are believed to induce or exacerbate a range of skin conditions, such as aging, inflammatory diseases (atopic dermatitis, cellulitis, and psoriasis), acne, hair loss, and even skin cancers (mainly melanoma and Squamous Cell Carcinoma) through various mechanisms. The interaction between pollutants and the skin might differ based on each agent's particular characteristics. Also, damaging the skin barrier seems to be closely related to the increased production of reactive oxygen species (ROS), induction of oxidative stress, activation of aryl hydrocarbon receptor (AhR), and inflammatory cytokines. This article reviews recent studies on the correlation between air pollutants and skin diseases, along with related mechanisms.

The novel coronavirus disease 2019 (COVID-19), caused by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), first appeared in December 2019, in Wuhan, China and evolved into a pandemic. As Angiotensin-Converting Enzyme 2 (ACE2) is one of the potential target receptors for SARS-CoV-2 in human body, which is expressed in different tissues, multiple organs might become affected. In the initial phase of the current pandemic, a handful of post-mortem case-series revealed COVID-19-related pathological changes in various organs. Although pathological examination is not a feasible method of diagnosis, it can elucidate pathological changes, pathogenesis of the disease, and the cause of death in COVID-19 cases. Herein, we thoroughly reviewed multiple organs including lung, gastrointestinal tract, liver, kidney, skin, heart, blood, spleen, lymph nodes, brain, blood vessels, and placenta in terms of COVID-19-related pathological alterations. Also, these findings were compared with SARS and MERS infection, wherever applicable. We found a diverse range of pathological changes, some of which resemble those found in SARS and MERS.

In-hospital transmission is one of the main routes of the 2019 novel coronavirus (SARS-CoV-2) spreading among health care workers (HCWs) who are the frontline fighters. However, coming into contact with COVID-19-positive patients is unavoidable. Therefore, hand hygiene is of utmost importance for the prevention of COVID-19 among HCWs. This purpose can be achieved by applying alcohol-based hand rubs, washing hands properly with soap and water, and applying other antiseptic agents. Nevertheless, regular hand hygiene could also be challenging, because water, detergents, and disinfectants may predispose HCWs to hand dermatitis. The current article reviews the risk factors for the development of hand dermatitis, with further focus on the most common agents used among HCWs. In addition, the risk of occupational hand dermatitis for each agent is evaluated to increase awareness of this common condition. Finally, some recommendations are discussed to reduce the effect of hand dermatitis on HCWs.

Background Ivermectin (IVM) was first used as an antiparasitic agent; however, the role of this drug evolved into a broad spectrum. Many mechanisms have been proposed, including interaction with the GABAergic system. Considering the presence of GABA receptor in the skin tissue and its role in ischemia-reperfusion I/R injury, we aimed to evaluate the effect of IVM through GABA receptors on random-pattern skin flap survival. Methods Sixty Wistar male rats were used. Multiple doses of IVM (0.01, 0.05, 0.2, and 0.5 mg/kg) were injected intraperitoneally before the surgery. Baclofen (selective GABAB agonist) and bicuculline (selective GABAA antagonist) were administered in combination with IVM to assess the role of the GABAergic system. Histopathological evaluations, immunohistochemical staining, quantitative assessment of IL-1β and TNFα, and the expression of GABAA α1 subunit and GABAB R1 receptors were evaluated in the skin tissue. Results IVM 0.05 mg/kg could significantly increase flap survival compared with the control group (P Conclusions IVM could improve skin flap survival, probably mediated by the GABAergic pathway. Both GABAA and GABAB receptors are involved in this process. This finding may repurpose the use of old drug, “Ivermectin.”

Background Breast-conserving surgery, especially with oncoplastic breast surgery (OBS), is becoming the standard of care in the surgical management of breast cancer. We investigated the applied technique of OBS and oncologic outcomes in a large series of patients. Patients and Methods This study was conducted between January 2008 and June 2018 in two centers in Iran. Patients underwent OBS. Early and late postoperative complications, oncologic outcomes, and follow-up data were documented. Results Nine hundred thirty-seven patients with a mean ± standard deviation age of 48.1 ± 11.3 underwent OBS. Most of the patients were diagnosed with early-stage disease, of which the most common pathology was invasive ductal carcinoma (83.3%). Lateral oncoplasty was the most commonly used OBS technique (324 cases, 34.6%). The most common complication was seroma formation. Reduction-type OBS technique had the highest rate of complications (13.1%). Thirty-four patients (5.4%) experienced local recurrence, with a median recurrence time of 26.4 months. Nine patients (1.3%) died from cancer recurrence. Conclusion OBS is a safe procedure with minor complications and good oncologic outcomes. These techniques can be applied to most patients who are candidates for breast-conserving surgery.

Protecting healthcare workers (HCWs) is crucial during Corona Virus Disease 2019 pandemic and requires wearing personal protective equipment (PPE) [1]. While most of the studies have focused on the skin reactions caused by gloves, other PPE such as gowns, respirator masks, face shields and goggles are also worn by HCWs for long hours during the current epidemic and skin irritations caused by these equipment may cause discouragement of health workers from using them [2]. In this letter we have focused on the reaction caused by non‐glove PPE.

Dear Editor,Treatment of pemphigus vulgaris (PV) patients, as a chronic bullous disease, with immunosuppressive agents could affect the course of COVID-19 (1). Nowadays, rituximab, an anti-CD20 mon...

To the Editor,Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) first appeared in Wuhan, China in December 2019 resulting in the COVID-19 pandemic. It has been shown that SARS-CoV-2 spik...

Sir,The immunosuppressive drugs used for the treatment of psoriasis may affect the clinical presentation and outcome of COVID-19 infection (1). Herein, we report a 73-year-old male patient with sev...

Background Protective helmets may reduce the risk of death and head injury in motorcycle collisions. However, there remains a large gap in knowledge regarding the effectiveness of different types of helmets in preventing injuries. Objective To explore and evaluate the effectiveness of different types of motorcycle helmets; that is the association between different helmet types and the incidence and severity of head, neck, and facial injuries among motorcyclists. Also, to explore the effect of different helmet types on riders. Methods A systematic search of different scientific databases was conducted from 1965 to April 2019. A scoping review was performed on the included articles. Eligible articles were included regarding defined criteria. Study characteristics, helmet types, fixation status, retention system, the prevention of injury or reduction of its severity were extracted. Results A total of 137 studies were included. There was very limited evidence for the better protection of full-face helmets from head and facial injury compared to open-face and half-coverage helmets. There was however scarce evidence for the superiority of a certain helmet type over others in terms of protection from neck injury. The retention system and the fixation status of helmets were two important factors affecting the risk of head and brain injury in motorcyclists. Helmets could also affect and limit the riders in terms of vision, hearing, and ventilation. Multiple solutions have been discussed to mitigate these effects. Conclusion Full-face helmets may protect head and face in motorcycle riders more than open-face and half-coverage helmets, but there is not enough evidence for better neck protection among these three helmet types. Helmets can affect the rider’s vision, hearing, and ventilation. When designing a helmet, all of these factors should be taken into account.

The effect of negative ions on the density, temperature, and potential of plasma in a direct current discharge regime has been studied experimentally. Nitrogen as an electronegative gas was used to produce negative ions in the plasma. Langmuir probe was employed to measure plasma parameters. Discharge was performed in an evacuated glass tube, with circular disk electrodes at different pressures. To obtain the spatial variation of plasma characters, measurements were done at different points on the axis of discharge tube. Argon and nitrogen gases were used as the working gas, and plasma current was kept constant at 5 mA during the experiments. Discharge voltage decreased sharply with increasing pressure for both argon and nitrogen plasmas; however, to sustain the discharge at constant current in nitrogen plasma, higher voltage was required in comparison with argon plasma. The plasma electron density was decreased from cathode to anode during the discharge process, while electron temperature was increased. Results confirm that nitrogen plasma contains negative ions, and discharge process is influenced by them noticeably.