Study of Culture Conversion in Drug-Resistant Pulmonary Tuberculosis on All-Oral Longer Regimen at IGIMS, Patna.

Background: Multidrug-resistant tuberculosis (MDR-TB) refers to tuberculosis that resists at least two primary drugs, namely isoniazid and rifampicin. To assess the management of MDR-TB, sputum culture conversion is performed. This study aimed to determine the culture conversion status of MDR-TB patients undergoing an all-oral longer regimen. Methods: This research constitutes an observational and prospective study conducted within a hospital setting. The study was done at the Department of Microbiology, IGIMS, Patna, from October 2020 to March 2022. Culture conversion in multidrug resistance pulmonary tuberculosis on all-oral longer regimens took one spot and one morning sample of sputum as per standard protocol after completing two months of all-oral longer regimens and culturing it in liquid broth using Mycobacterium Growth Indicator Tube (MGIT) 960 System at two, four then six months till we got a negative result. Results: Maximum number of the cases, 77 (74.8%), belonged to 19-35 years of age group. Males were 68 (66.1%) and females were 35 (33.9%), respectively, with male to female ratio of 1.9:1. After 2 months of oral longer regimen treatment, out of 103 cases, we found 98 (95.1%) patients had sputum for culture positive and only five (4.2%) patients had sputum for culture negative. After 6 months of oral longer regimen treatment, out of 101 cases, we found 16 (15.8%) patients had sputum for culture positive and 85 (85.2%) patients had sputum for culture negative. Conclusion: In patients with multidrug-resistant pulmonary tuberculosis (MDR-TB) who received an all-oral longer regimen, the introduction of bedaquiline led to positive outcomes as evidenced by a greater number of negative sputum cultures, a decrease in culture reversions, and a reduced risk of developing a more resistant form of MDR-TB.

Application of Oncolytic Poxviruses: An Emerging Paradigm in Cancer Therapy.

Despite the significant advancement of new tools and technology in the field of medical biology and molecular biology, the challenges in the treatment of most cancer types remain constant with the problem of developing resistance toward drugs and no substantial enhancement in the overall survival rate of cancer patients. Immunotherapy has shown the most promising results in different clinical and preclinical trials in the treatment of various cancer due to its higher efficacy and minimum collateral damage in many cancer patients as compared to conventional chemotherapy and radiotherapy. An oncolytic virus is a new class of immunotherapy that can selectively replicate in tumor cells and destroy them by the process of cell lysis while exerting minimum or no effect on a normal cell. Besides this, it can also activate the host's innate immune system, which generates an anti-tumor immune response to eliminate the tumor cells. Several wild types and genetically modified viruses have been investigated to show oncolytic behavior. Vaccinia virus has been studied extensively and tested for its promising oncolytic nature on various model systems and clinical trials. Recently, several engineered vaccinia viruses have been developed that express the desired genes encoded for selective penetration in tumor cells and enhanced activation of the immune system for generating anti-tumor immunity. However, further investigation is required to prove their potential and enhance their therapeutic efficacy.

Poxviruses as Agents of Biological Warfare: The Importance of Ensuring Ethical Standards for Research with Viruses.

Historically, biological agents have been used to target various populations. One of the earliest examples could be the catastrophic effect of smallpox in Australia in the eighteenth century (as alleged by some historians). Modern biological techniques can be used to both create or provide protection against various agents of biological warfare. Any microorganism (viruses, bacteria, and fungi) or its toxins can be used as biological agents. Minnesota Department of Health has listed Smallpox (variola major) as a category A bioterrorism agent, even though it has been eradicated in 1980 through an extensive vaccination campaign. Category A agents are considered the highest risk to public health. Laboratory-associated outbreaks of poxviruses could cause unprecedented occupational hazards. Only two WHO-approved BSL-4 facilities in the United States and Russia are allowed to perform research on the variola virus. So, poxviruses present themselves as a classical case of a dual-use dilemma, since research with them can be used for both beneficial and harmful purposes. Although the importance of ethics in scientific research requires no further elaboration, ethical norms assume greater significance during experimentation with poxviruses. In this chapter, we will update the readers on the sensitive nature of conducting research with poxviruses, and how these viruses can be a source of potential biological weapons. Finally, specified ethical guidelines are explored to ensure safe research practices in virology.

Amyloidogenic Propensity of Metabolites in the Uric Acid Pathway and Urea Cycle Critically Impacts the Etiology of Metabolic Disorders.

Novel insights into the etiology of metabolic disorders have recently been uncovered through the study of metabolite amyloids. In particular, inborn errors of metabolism (IEMs), including gout, Lesch-Nyhan syndrome (LNS), xanthinuria, citrullinemia, and hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome, are attributed to the dysfunction of the urea cycle and uric acid pathway. In this study, we endeavored to understand and mechanistically characterize the aggregative property exhibited by the principal metabolites of the urea cycle and uric acid pathway, specifically hypoxanthine, xanthine, citrulline, and ornithine. Employing scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM), we studied the aggregation profiles of the metabolites. Insights obtained through molecular dynamics (MD) simulation underscore the vital roles of π-π stacking and hydrogen bonding interactions in the self-assembly process, and thioflavin T (ThT) assays further corroborate the amyloid nature of these metabolites. The in vitro MTT assay revealed the cytotoxic trait of these assemblies, a finding that was substantiated by in vivo assays employing the Caenorhabditis elegans (C. elegans) model, which revealed that the toxic effects were more pronounced and dose-specific in the case of metabolites that had aged via longer preincubation. We hence report a compelling phenomenon wherein these metabolites not only aggregate but transform into a soft, ordered assembly over time, eventually crystallizing upon extended incubation, leading to pathological implications. Our study suggests that the amyloidogenic nature of the involved metabolites could be a common etiological link in IEMs, potentially providing a unified perspective to study their pathophysiology, thus offering exciting insights into the development of targeted interventions for these metabolic disorders.

Comparison of Cytokines Profiles and Monocyte Response Among Tuberculosis Patients Versus Patients Coinfected With Intestinal Helminth and Tuberculosis.

Background Tuberculosis (TB) and intestinal helminth infections often coexist, posing a significant health challenge. TB, caused by Mycobacterium tuberculosis, and helminths elicit distinct immune responses - Th1 for TB and Th2 for helminths. Co-infection introduces a complex immunological challenge, potentially compromising TB control. This study addresses the research gap by comparing cytokine profiles and monocyte responses in TB patients, helminth-infected individuals, and those with both. Insights gained may enhance diagnosis, treatment, and disease control strategies where TB and helminths prevail. Methods A cross-sectional observational study conducted at Indira Gandhi Institute of Medical Sciences, Patna, Bihar, aimed to compare cytokine profiles and monocyte responses in TB patients and those coinfected with TB and helminths. The study included 150 newly diagnosed active TB individuals aged 18 to 65 years. TB diagnosis was confirmed through clinical assessment, sputum microscopy, and GeneXpert (Cepheid, Sunnyvale, CA, USA) testing. Stool examination employed various methods, including the Kato-Katz technique and formalin-ether concentration. Blood samples were collected for hematological analysis, cytokine profiling, and monocyte isolation. Statistical analysis, using SPSS version 20.0 (IBM Corp., Armonk, NY, USA), included descriptive statistics, and t-test analyses. Results In our study of 150 participants, half (50.0%) showed positive helminth status. The sociodemographic analysis revealed no significant differences in age, gender, education, occupation, marital status, smoking, alcohol, BMI, diabetes, and hypertension between TB patients (n=75) and TB+Helminth patients (n=75), ensuring baseline matching. The prevalence of specific helminth infections in TB+Helminth patients included Ascaris lumbricoides (24.0%), Trichuris trichiura (18.7%), and others. Hematological parameters showed significant differences, with TB+Helminth patients exhibiting higher RBC count, hemoglobin, hematocrit, neutrophil count, and monocyte count; also eosinophil count was more raised in TB+Helminth patients (0.36 x 103/µL) when compared to TB patients (0.25 x 103/µL). Cytokine profiles and monocyte responses varied significantly between the groups, with TB patients having higher IL-4, IL-6, IFN-γ, TNF-α, and IL-1ß levels, while TB+Helminth patients had elevated IL-10. Monocyte response time did not differ significantly. Conclusion The observed differences in hematological parameters and cytokine profiles emphasize the need for tailored approaches to diagnosis and treatment in co-infected individuals. These findings suggest that the management of TB patients should consider the potential influence of helminth co-infections.

The Trend of C-Reactive Protein After Corticosteroid Therapy in COVID-19 Patients Admitted to IGIMS, Patna.

BACKGROUND: C-reactive protein (CRP) is a routine inflammation biomarker. Increased CRP levels are correlated with COVID-19. We found a marked reduction in CRP concentration on corticosteroid therapy, which in turn led to reduced mortality and duration of hospital stay. METHODS: In this retrospective cohort study, CRP levels were measured on admission and at 72 hours and compared between two groups of patients, with and without corticosteroid therapy. The study sample consisted of 105 RT-PCR-confirmed patients admitted to the ICU of the COVID ward. Out of the total patients, 57 received one or more doses of dexamethasone in addition to usual treatment, and 48 were given only usual care. RESULT: CRP at the time of admission was comparable for both groups. Also, a significant decrease in the CRP was noted in both groups 72 hours post-admission. Moreover, the decline was more marked in the steroid-administered group (CRP-baseline: 34.3mg/dL (+/-8.44), CRP at 72 hours 18.5mg/dL(+/-7.95) (p <0.00) compared to non-steroid group (CRP_baseline: 34.04mg/dL (+/-10.06), CRP at 72. Those with comorbidities were administered steroids (n=38, 66.7%) compared to those who were not (n=08, 16.7%). The average duration of hospital stay was less (5 to 7 days) in the corticosteroid-administered group compared to the other group (7 to 10 days). CONCLUSION: Routine CRP tests can predict the outcome and treatment of severe coronavirus disease. Corticosteroid treatment in COVID-19 patients is associated with reduced CRP levels within 72 hours after therapy.

Assessment of Changes in the Upper Airway in Children with Finger Sucking Habit Using Cephalometric Radiographs.

Introduction: The persistence of the sucking beyond a certain age has been attributed to many deleterious effects on the orofacial structures. Hence, the present study evaluates the alterations in the upper airway among the children with and without the finger-sucking habits. Material and Methods: We piloted an observational study among 58 children with malocclusion who required orthodontic treatment, in which between 7 and 12 years were selected. They were subjected to lateral cephalometric radiographs, and cephalometric analysis of craniofacial morphology, tongue posture, hyoid bone position, upper airway, and head posture was performed and analyzed using independent t-test. Results: In the children with finger-sucking habit group, not only the maxilla was placed anteriorly in relation to the cranial base, but also increased Abstract xi in the length of the palate and the tongue posture. No significant alterations were seen in other parameters. Conclusion: Changes were evident among the children with finger-sucking habits for the craniofacial morphology, tongue posture, upper airway, and head posture with no alteration in the hyoid bone position.

Fabrication and mechanical characterization of hydrogel-based 3D cell-like structures.

In this article, we demonstrate the fabrication of 3D cell-like structures using a femtosecond laser-based two-photon polymerization technique. By employing poly(ethylene glycol) diacrylate monomers as a precursor solution, we fabricate 3D hemispheres that resemble morphological and biomechanical characteristics of natural cells. We employ an optical tweezers-based microrheology technique to measure the viscoelastic properties of the precursor solutions inside and outside the structures. In addition, we demonstrate the interchangeability of the precursor solution within fabricated structures without impairing the microstructures. The combination of two-photon polymerization and microrheological measurements by optical tweezers demonstrated here represents a powerful toolbox for future investigations into cell mimic and artificial cell studies.

Clinical and CBCT Assessment of Crestal Bone Changes in Immediate and Delayed Placement of Implant.

Objectives: The present research was done to assess the crestal bone changes in immediate and delayed dental implant placement. Materials and Method: Twenty four implant sites in participants within the age group of 25-60 years in both genders were done with immediate (Group I) and delayed implant (Group II) placement method. Clinical parameters such as pain, mobility, and radiographic assessment for crestal bone alterations were recorded at baseline, 3 months, and 6 months. Results and Conclusion: On intergroup assessment, the mean variation of the pain, mobility, and crestal bone loss was insignificant.

Post-COVID-19 cavitary lung lesion due to Aspergillus flavus and Enterobacter cloacae in a patient suffering from COVID-19 pneumonia - a case report.

The coronavirus disease 2019 (COVID-19) pandemic has manifested as a multifaceted paradigm but has primarily affected the respiratory system. Though a rare sequela after-COVID-19, we present a case of cavitary lung lesion in an adult patient, which manifested with common symptoms such as fever, cough and dyspnoea during the post-COVID-19 recovery period. Aspergillus flavus and Enterobacter cloacae were found to be the main causative organisms. Fungal and bacterial coinfection may be thought of in similar situations and appropriate treatment may be given to prevent further morbidity and mortality.

Strategic implants and bone morphogenic changes: Survival and clinical success in long-term.

Dental implants are one of the established treatment protocols to replace/restore lost tooth/teeth structures. Ihde and Ihde redefined concept of strategic implantology based on immediate loading. The aim of present case series was to evaluate efficacy of strategic implants regarding primary stability, quality of bone, survival, and clinical success in long-term. The present case series included a total of 26 patients aged 40 to 70 years restored with strategic implants after an immediate loading protocol. On follow-up visits, clinical assessment of implant stability was done by absence of implant mobility and absence of pain and dysesthesia while radiographically, immediate postoperative crestal bone level was compared with that observed on follow-up visits. Also, integration of apical and/or crestal threads of implants were assessed radiographically for any signs of radiolucency along with healing of sockets and crestal bone levels in relation to abutment margins.

The long-term impact of coronavirus disease 2019 on environmental health: a review study of the bi-directional effect.

Background: When health systems worldwide grapple with the coronavirus disease 2019 (COVID-19) pandemic, its effect on the global environment is also a significant consideration factor. It is a two-way process where the pre-COVID climate factors influenced the landscape in which the disease proliferates globally and the consequences of the pandemic on our surroundings. The environmental health disparities will also have a long-lasting effect on public health response. Main body: The ongoing research on the novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and COVID-19 must also include the role of environmental factors in the process of infection and the differential severity of the disease. Studies have shown that the virus has created positive and negative ramifications on the world environment, especially in countries most critically affected by the pandemic. Contingency measures to slow down the virus, such as self-distancing and lockdowns have shown improvements in air, water, and noise quality with a concomitant decrease in greenhouse gas emissions. On the other hand, biohazard waste management is a cause for concern that can result in negative effects on planetary health. At the peak of the infection, most attention has been diverted to the medical aspects of the pandemic. Gradually, policymakers must shift their focus to social and economic avenues, environmental development, and sustainability. Conclusion: The COVID-19 pandemic has profoundly impacted the environment, both directly and indirectly. On the one hand, the sudden halt in economic and industrial activities led to a decrease in air and water pollution, as well as a reduction in greenhouse gas emissions. On the other hand, the increased use of single-use plastics and a surge in e-commerce activities have had negative effects on the environment. As we move forward, we must consider the pandemic's long-term impacts on the environment and work toward a more sustainable future that balances economic growth and environmental protection. The study shall update the readers on the various facets of the interaction between this pandemic and environmental health with model development for long-term sustainability.

Marker assisted stacking of Ty3, Mi1.2 and Ph3 resistance alleles for leaf curl, root knot and late blight diseases in tomato.

Developing multiple disease resistance through naturally available host resistance alleles is a challenging as well as rewarding area of research. Availability of host resistance alleles and the reliability of their identification through diagnostic molecular markers have paved the way for stacking of these resistance alleles for developing important genetic resources in tomato. Here we report the marker assisted stacking of Ty3, Mi1.2 and Ph3 alleles, governing leaf curl, root knot and late blight disease resistance, respectively, in superior F4 segregants of tomato derived from two diverse parents (i.e., BRDT-1 and H-88-78-1). Marker assisted selection was applied only on morphologically superior segregants at F2 and F3 generations, which helped us in identifying suitable lines even from a relatively small population. The diagnostic values of the employed molecular markers advocate that the identified superior segregants, carrying all the three aforementioned resistance alleles in homozygous condition, are suitable to be explored as valuable genetic resources for developing multiple disease resistance through rapid introgression of these genes in different genetic background of tomato. Identification of suitable segregants derived from these lines should be promising for obtaining improved cultivars in near future. Nevertheless, these lines might be further explored to decipher the intrinsic details of host's resistance mechanism involving genetic interactions between different resistance factors. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01277-2.

Determinants of menstrual hygiene among adolescent school girls in a rural area of Patna, Bihar, India: A cross-sectional study.

Background: Adolescence is a transitional phase marked by the onset of menarche. Most adolescent girls have incomplete or inaccurate information about menstrual physiology and hygiene. There are several misconceptions and taboos linked with it, resulting in adverse health outcomes. However, numerous factors associated with menstrual hygiene are modifiable. If these are adequately identified and addressed, it can empower young girls to lead healthy life in a positive environment. Aims and Objectives: (1) To assess the knowledge and practices regarding menstrual hygiene among adolescent school girls. (2) To determine the association of menstrual hygiene practices with sociodemographic and related factors. Materials and Methods: A descriptive cross-sectional study was conducted in rural Patna, Bihar, in which 300 eligible adolescent school-going menstruating girls (13-17 years) were recruited from four schools. They were interviewed using a predesigned questionnaire, and relevant information on sociodemographic profiles and menorrhoeal characteristics was obtained. Median scores were calculated for the knowledge and practices domain. Multiple logistic regression was used to determine the associated factors of menstrual hygiene practice. Results: The mean age of girls was 14 ± 1.07 years, while the mean age of menarche was 12.37 ± 0.92 years. More than half (59.3%) were found to possess good knowledge (scores 7 and above) regarding menstruation and its physiology. Half (50.3%) of the girls had good menstrual hygiene practices (scores 9 and above). Multiple logistic regression model revealed that adolescent girls studying in government schools (AOR = 0.05, CI = 0.02-0.12) and those living in nuclear families (AOR = 0.05, CI = 0.02-0.12) were likely to be significantly associated with poor menstrual hygiene practices. Conclusion: Menstrual hygiene is still far from satisfactory; hence, it should be a vital aspect of the school health educational curriculum. There is an imperative need to design acceptable awareness/advocacy programs for adolescent girls in the future.

Robust Tipless Positioning Device for Near-Field Investigations: Press and Roll Scan (PROscan).

Scanning probe microscopes scan and manipulate a sharp tip in the immediate vicinity of a sample surface. The limited bandwidth of the feedback mechanism used for stabilizing the separation between the tip and the sample makes the fragile nanoscopic tip very susceptible to mechanical instabilities. We propose, demonstrate, and characterize an alternative device based on bulging a thin substrate against a second substrate and rolling them with respect to each other. We showcase the power of this method by placing gold nanoparticles and semiconductor quantum dots on the two opposite substrates and positioning them with nanometer precision to enhance the fluorescence intensity and emission rate. Furthermore, we exhibit the passive mechanical stability of the system over more than 1 h. Our design concept finds applications in a variety of other scientific and technological contexts, where nanoscopic features have to be positioned and kept near contact with each other.

Expression of podoplanin in tumor cells and lymphatic vessels in both tumoral and peritumoral areas and correlation with metastatic potential of oral squamous cell carcinoma.

AIM: This study aims to study the expression of podoplanin in tumor cells as well as the lymphatic vessels (LVs) in both tumoral and peritumoral areas and correlate the importance of the lymphatic microvascular density (LMVD) in oral squamous cell carcinoma (OSCC) and its metastatic potential. MATERIALS AND METHODS: D2-40 expression and LV density (LVD) were assessed using antibody D240, in 45 diagnosed cases of all the three grades of OSCC. D2-40 expression was evaluated in both epithelial cells as well as the LVs. RESULTS: D2-40 expression in OSCC showed two different patterns - diffuse and focal. LMVD was calculated and difference in peritumoral and intra tumoral LVs was also assessed. A marked increase was seen we progressed from well-differentiated tumor to poorly differentiated ones, but this difference was found to be statistically nonsignificant. D2-40 immunostaining also highlighted the presence of lymphatic invasion present within the tumors which was detected by the presence of tumor emboli within the LVs. Overall, no significant correlation was found between D240 epithelial positivity and LVD. CONCLUSION: The expression of podoplanin in tumor cells and lymphatics when correlated with histopathological status and clinically with the lymph node status can definitely help in the adjuvant therapies used in OSCC.

Assessment of C-Reactive Protein Level in Oral Submucous Fibrosis and Oral Squamous Cell Carcinoma Patient.

BACKGROUND: Potentially malignant disorders are highly prevalent in India. In this study, we assessed C-reactive protein (CRP) levels in patients with oral submucous fibrosis (OSMF) and oral squamous cell carcinoma (OSCC). METHODOLOGY: Sixty-four patients (OSMF and OSCC) were undertaken and were classified into 3 groups, OSMF patients (Group I, 34), OSCC (Group II, 30), and healthy controls (Group III, 26). Immunoturbidimetry method was used for the estimation of CRP levels. RESULTS: Maximum cases in Group I was seen in the age group 40-60 years (males-10, females-3), Group II in the age group 40-60 years (males-11, females-5) and Group III (males-5, females-6). The mean CRP level in Group I was 6.12 ± 4.5 mg/l, in Group II was 28.4 ± 21.5 mg/l, and in Group III was 3.15 ± 2.19 mg/l. The difference was significant (P < 0.05). CONCLUSION: Authors found that OSMF and oral cancer patients had increased CRP levels as compared to healthy subjects.

Multi-frequency passive and active microrheology with optical tweezers.

Optical tweezers have attracted significant attention for microrheological applications, due to the possibility of investigating viscoelastic properties in vivo which are strongly related to the health status and development of biological specimens. In order to use optical tweezers as a microrheological tool, an exact force calibration in the complex system under investigation is required. One of the most promising techniques for optical tweezers calibration in a viscoelastic medium is the so-called active-passive calibration, which allows determining both the trap stiffness and microrheological properties of the medium with the least a-priori knowledge in comparison to the other methods. In this manuscript, we develop an optimization of the active-passive calibration technique performed with a sample stage driving, whose implementation is more straightforward with respect to standard laser driving where two different laser beams are required. We performed microrheological measurements over a broad frequency range in a few seconds implementing an accurate multi-frequency driving of the sample stage. The optical tweezers-based microrheometer was first validated by measuring water, and then exemplarily applied to more viscous medium and subsequently to a viscoelastic solution of methylcellulose in water. The described method paves the way to microrheological precision metrology in biological samples with high temporal- and spatial-resolution allowing for investigation of even short time-scale phenomena.

Evaluation of Hydroxyapatite Granules, CERAMENT™, and Platelet-rich Fibrin in the Management of Endodontic Apical Surgery.

AIM: The present study compared hydroxyapatite granules, CERAMENT™, and platelet-rich fibrin (PRF) in the management of endodontic apical surgery cases. MATERIALS AND METHODS: The present study was conducted on 126 patients requiring apical surgery of both genders. Patients were treated with hydroxyapatite granules, CERAMENT™, and PRF and were recalled regularly for assessment of pain, mobility, presence or absence of sinus, and healing site. RESULTS: The mean days taken for the disappearance of pain in group I was 51.2 days, in group II was 52.3 days, and in group III was 44.7 days. The difference was significant (p < 0.05). There was a less number of draining sinuses in II and III groups. This was statistically significant (p < 0.05). Significantly less area remained after surgical intervention in groups II and III compared to group I recorded at follow-up period. The difference was significant (p < 0.05). CONCLUSION: Authors found PRF superior in terms of reducing pain, mobility, and sinus and improving the healing site as compared to hydroxyapatite and CERAMENT™. CLINICAL SIGNIFICANCE: Platelet-rich fibrin is considered more superior in terms of reducing pain, mobility, and sinus and improving the healing site, and it can be advised in clinical practice for endodontic management.

Reduction in generalized conductance with increasing gain in amplifying Anderson-localized systems.

The consequences of a nonconservative environment on the transport of photons under conditions of Anderson localization in a disordered system are a topic of great interest. In this work, we experimentally demonstrate the systematic decrease in the localization length of a quasi-one-dimensional localizing system when gain is added to it. We quantify the generalized conductance of the system using the variance of the fluctuations in the localized eigenfunctions and show a decrease in conductance with gain. We theoretically model this system using a combination of transfer matrix calculations and rate equations for a two-level lasing system and find very good qualitative agreement with the experimental results. We show that the generalized conductance in higher disorder can be emulated in weak disorder using the appropriate gain. The decreasing conductance is explained using the reduced probability of outcoupling of photons relative to their peak position within the system.