Single-Grating Monolithic Spatial Heterodyne Raman Spectrometer: An Investigation on the Effects of Detector Selection

Spatial heterodyne Raman spectrometers (SHRSs) are modified forms of Michelson interferometers, except the mirrors in a Michelson interferometer are replaced with stationary diffraction gratings. This design removes the need for an entrance slit, as is the case in a dispersive spectrometer, and removes the need to scan the spectrum by using a moving mirror in a modern Michelson interferometer. In previous studies, various SHRS variants, such as free-standing two-grating SHRS, single-grating SHRS (1g-SHRS), monolithic SHRS (mSHRS), and single-grating mSHRS (1g-mSHRS), have been evaluated. However, the present study exclusively focuses on the 1g-mSHRS configuration. The 1g-mSHRS and 1g-SHRS increase the spectral range at fixed grating line density while trading off spectral resolution and resolving power. The mSHRS benefits from increased rigidity, lack of moving parts, and reduced footprint. In this study, we investigate how the choice of detector impacts the performance of the 1g-mSHRS system, with a specific focus on evaluating the performance of three types of cameras: charged-coupled device (CCD), intensified CCD (ICCD), and complementary metal-oxide-semiconductor (CMOS) cameras. These systems were evaluated using geological, organic, and inorganic samples using a 532 nm continuous wave laser for the CMOS and CCD cameras, and a 532 nm neodymium-doped yttrium aluminum garnet pulsed laser for the ICCD camera. The footprint of the 1g-mSHRS was 3.5 × 3.5 × 2.5 cm3 with a mass of 272 g or 80 g, depending on whether the monolith housing is included or not. We found that increasing the number of pixels utilized along the x-axis of the camera increases fringe visibility (FV) and optimizes the resolution (by capturing the entirety of the grating and magnifying the fringes). The number of pixels utilized in the y-axis, chip size, and dimensions, affect the signal-to-noise ratio of the systems. Additionally, we discuss the effect of pixel pitch on the recovery of Fizeau fringes, including the relationship between the Nyquist frequency, aliasing, and FV.

Remote Raman Sensing Using a Single-Grating Monolithic Spatial Heterodyne Raman Spectrometer: A Potential Tool for Planetary Exploration

Advances in Raman instrumentation have led to the implementation of a remote dispersive Raman spectrometer on the Perseverance rover on Mars, which is used for remote sensing. For remote applications, dispersive spectrometers suffer from a few setbacks such as relatively larger sizes, low light throughput, limited spectral ranges, relatively low resolutions for small devices, and high sensitivity to misalignment. A spatial heterodyne Raman spectrometer (SHRS), which is a fixed grating interferometer, helps overcome some of these problems. Most SHRS devices that have been described use two fixed diffraction gratings, but a variance of the SHRS called the one-grating SHRS (1g-SHRS) replaces one of the gratings with a mirror, which makes it more compact. In a recent paper we described monolithic two-gratings SHRS, and in this paper, we investigate a single-grating monolithic SHRS (1g-mSHRS), which combines the 1g-SHRS with a monolithic setup previously tested at the University of South Carolina. This setup integrates the beamsplitter, grating, and mirror into a single monolithic device. This reduces the number of adjustable components, allows for easier alignment, and reduces the footprint of the device (35 × 35 × 25 mm with a weight of 80 g). This instrument provides a high spectral resolution (∼9 cm^-1) and large spectral range (7327 cm^-1) while decreasing the sensitivity to alignment with a field of view of 5.61 mm at 3m. We discuss the characteristics of the 1g-mSHRS by measuring the time-resolved remote Raman spectra of a few inorganic salts, organics, and minerals at 3 m. The 1g-mSHRS makes a good candidate for planetary exploration because of its large spectral range, greater sensitivity, competitively higher spectral resolution, low alignment sensitivity, and high light throughput in a compact easily aligned system with no moving parts.

Compact Color Biofinder (CoCoBi): Fast, Standoff, Sensitive Detection of Biomolecules and Polyaromatic Hydrocarbons for the Detection of Life

We have developed a compact instrument called the "COmpact COlor BIofinder", or CoCoBi, for the standoff detection of biological materials and organics with polyaromatic hydrocarbons (PAHs) using a nondestructive approach in a wide area. The CoCoBi system uses a compact solid state, conductively cooled neodymium-doped yttrium aluminum garnet (Nd:YAG) nanosecond pulsed laser capable of simultaneously providing two excitation wavelengths, 355 and 532 nm, and a compact, sensitive-gated color complementary metal-oxide-semiconductor camera detector. The system is compact, portable, and determines the location of biological materials and organics with PAHs in an area 1590 cm2 wide, from a target distance of 3 m through live video using fast fluorescence signals. The CoCoBi system is highly sensitive and capable of detecting a PAH concentration below 1 part per billion from a distance of 1 m. The color images provide the simultaneous detection of various objects in the target area using shades of color and morphological features. We demonstrate that this unique feature successfully detected the biological remains present in a 150-million-year-old fossil buried in a fluorescent clay matrix. The CoCoBi was also successfully field-tested in Hawaiian ocean water during daylight hours for the detection of natural biological materials present in the ocean. The wide-area and video-speed imaging capabilities of CoCoBi for biodetection may be highly useful in future NASA rover-lander life detection missions.

Underwater Time-Gated Standoff Raman Sensor for In Situ Chemical Sensing

We describe the fabrication of an underwater time-gated standoff Raman sensor, consisting of a custom Raman spectrometer, custom scanner, and commercial diode-pumped pulsed 532 nm laser all located inside a pressure housing. The Raman sensor was tested in the laboratory with samples in air, a tank containing tap water and seawater, and in the coastal Hawaiian harbor. We demonstrate our new system by presenting standoff Raman spectra of some of the chemicals used in homemade explosive devices and improvised explosive devices, including sulfur, nitrates, chlorates, and perchlorates up to a distance of ∼6 m in seawater and tap water. Finally, the Raman spectra of these hazardous chemicals sealed inside plastic containers submersed in the Hawaiian Harbor water are also presented.

Detecting Minerals and Organics Relevant to Planetary Exploration Using a Compact Portable Remote Raman System at 122 Meters

Raman spectroscopy is a technique that can detect and characterize a range of molecular compounds such as water, water ice, water-bearing minerals, and organics of particular interest to planetary science. The detection and characterization of these molecular compounds, which are indications of habitability on planetary bodies, have become an important goal for planetary exploration missions spanning the solar system. Using a compact portable remote Raman system consisting of a 532 nm neodymium-doped yttrium aluminum garnet- (Nd:YAG-) pulsed laser, a 3-in. (7.62 cm) diameter mirror lens and a compact spectrograph with a miniature intensified charge coupled device (mini-ICCD), we were able to detect water (H₂O), water ice (H₂O-ice), CO₂-ice, hydrous minerals, organics, nitrates, and an amino acid from a remote distance of 122 m in natural lighting conditions. To the best of our knowledge, this is the longest remote Raman detection using a compact system. The development of this uniquely compact portable remote Raman system is applicable to a range of solar system exploration missions including stationary landers for ocean worlds and lunar exploration, as they provide unambiguous detection of compounds indicative of life as well as resources necessary for further human exploration.

Suppressing the Multiplex Disadvantage in Photon-Noise Limited Interferometry Using Cross-Dispersed Spatial Heterodyne Spectrometry

Spatial heterodyne spectrometers are members of the static Fourier transform class of spectrometers, well-regarded for their ability to acquire high-resolution, high wavelength precision emission spectra in compact, light footprint packages. In a spatial heterodyne spectrometer experiment, a Fizeau fringe is generated for every spectral feature in a given spectrum, and spatial heterodyne spectrometer records the superposition of all Fizeau fringes in the spectrum on a detector. Hence, the sensitivity of spatial heterodyne spectrometers is constrained by uncorrelated, multiplicative photon noise that limits the detection of spectral features to those that are more luminous than the square root of the total incident flux onto the detector. In essence, powerful spectral features create a rising floor of noise that wash out less luminous features. In the present work, we introduce a novel spectrometer coupling, that being an Amici prism spectrometer in series with spatial heterodyne spectrometer, that correlates photon shot noise along one axis of a detector that in turn suppresses multiplicative photon noise within each row of the interferogram image. We demonstrate that this spectrometer pairing facilitates the measurement of weak Raman spectral features that, in a traditional spatial heterodyne spectrometer measurement, would be washed out by multiplicative photon noise.

Remote Raman Detection of Chemicals from 1752 m During Afternoon Daylight

The detection and identification of materials from a distance is highly desirable for applications where accessibility is limited or there are safety concerns. Raman spectroscopy can be performed remotely and provides a very high level of confidence in detection of chemicals through vibrational modes. However, the remote Raman detection of chemicals is challenging because of the very weak nature of Raman signals. Using a remote Raman system, we performed fast remote detection of various solid and liquid chemicals from 1752 m during afternoon hours on a sunny day in Hawaii. Remote Raman systems with kilometer target range could be useful for chemical detection of volcanic gases, methane clathrate icebergs or fire ice, toxic gas clouds and toxic waste, explosives, and hazardous chemicals. With this successful test, we demonstrate the feasibility of developing future mid-size remote Raman systems suitable for long range chemical detection using helicopters and light airplanes.

Evaluation of a policy of total mesorectal excision for rectal and rectosigmoid cancers

BACKGROUND

Total mesorectal excision (TME) is advocated for rectal cancer but the indications and extent of resection vary widely between surgeons.

METHODS

Seventy-six consecutive patients (61 elective, 15 acute admission) with rectal or rectosigmoid cancer were admitted to a unit where TME was the preferred surgical option for potentially curative cancer at all levels of the rectum.

RESULTS

Procedures undertaken were anterior resection (38 patients), abdominoperineal resection (18), Hartmann's procedure (ten) and transanal excision (one). Six patients had proximal faecal diversion alone and surgery was withheld in three. Anastomotic leaks occurred in six of 37 patients who had anterior resection with primary anastomosis, resulting in one early death. The presence of a proximal stoma did not influence the rate or seriousness of anastomotic dehiscence. After potentially curative TME in 45 patients, there have been eight local recurrences, four associated with systemic metastases and four which occurred in isolation (median follow-up 34 months).

CONCLUSION

Curative TME was deemed appropriate in 59 per cent of unselected patients with rectal cancer. It was associated with few local recurrences but a morbidity rate that questions its role in treatment of upper third tumours.

Molecular biology and respiratory disease. 3. Evaluation of nucleolar organiser regions in pulmonary pathology

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Significance of venous and lymphatic invasion in malignant polyps of the colon and rectum

Three hundred and sixty seven neoplastic colorectal polyps removed at endoscopy of which 34 were complicated by invasive carcinoma, were reviewed clinically and histologically to assess the prevalence and clinical significance of venous and or lymphatic invasion. Traditional stains for histological assessment were supplemented by immunohistochemical methods. Venous and or lymphatic invasion was present in six cases (17.6%), with a statistically significant association with recurrent carcinoma or Dukes's C carcinoma in polyps otherwise regarded as completely excised. The presence or absence of venous and or lymphatic invasion in malignant polyps should be documented as if present, further treatment is indicated. A combination of haematoxylin and eosin and elastic-van Gieson stains will usually identify the presence of vascular invasion. Where a discrepancy arises, however, additional immunohistochemical stains may be of value.

How should we count AgNORS? Proposals for a standardized approach

There is interest currently in the AgNOR technique, for NOR-associated proteins. In some cases, this technique enables the distinction to be made between certain grades of malignancy and may enable prognostic assessment. This paper attempts to suggest a standardized means for the enumeration of NORs in histological sections. Attention should be paid to rigorous technique and careful resolution of intranucleolar AgNOR dots. The timing of the reaction and fixation methods are also most important.

Correlation between NOR sizes and numbers in non-Hodgkin's lymphomas

A series of 36 cases of non-Hodgkin's lymphomas (NHL) has been studied by means of the argyrophil (AgNOR) method for nuclear organizer regions (NORs). Morphometric analysis of highly magnified photographic images of light microscope preparations of the AgNORs was performed by means of an interactive image analysis system. It was observed that in the low-grade specimens (where NORs are less frequent than in those of high-grade histology), the AgNOR sites were highly significantly (P less than 0.001) larger than in high-grade NHL. In the low-grade lymphomas, the AgNOR maximum diameter (Dmax) ranged from 0.7 to 1.7 micron 2 (mean 1.11 micron 2) and area ranged from 0.48 to 1.99 micron 2 (mean 1.11 micron 2). In contrast, in the high-grade specimens, Dmax was from 0.33 to 0.51 micron (mean 0.41 micron) and the area ranged from 0.082 to 0.19 micron 2 (mean 0.13 micron 2). Thus, a well-defined inverse relationship was observed between AgNOR numbers and their sizes. There was total separation between low- and high-grade values in this series. This light microscope technique offers some advantages over ultrastructural morphometry of interphase NORs (fibrillar centres).

Prognostic importance of nucleolar organiser regions in embryonal rhabdomyosarcoma

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Nucleolar organizer regions in cutaneous tumours

A silver colloid technique to identify nucleolar organizer region associated protein (AgNOR) has been applied to 68 cutaneous tumours. Basal cell carcinomas, eccrine tumours, apocrine tumours, and hair follicle tumours had differences in their numbers of AgNORs; these appeared as small black dots in their nuclei. Dermatofibromas and squamous cell carcinomas showed a degree of variability in the number of AgNORs depending on the cellularity of the former and differentiation of the latter. Basal cell carcinomas possessed significantly many more AgNORs per nucleus than the other neoplasms. It is suggested that this technique, previously the province of the cytogeneticist, may be of use in the diagnosis of cutaneous neoplasms.

Nucleolar organiser regions in fibrous proliferations of childhood and infantile fibrosarcoma

A silver colloid technique to identify nucleolar organiser region associated protein (AgNOR) was applied to 16 fibrous proliferations of childhood and six low grade fibrosarcomas. The fibrous proliferations comprised five cases of infantile digital fibromatosis, seven of infantile desmoid type fibromatosis, and four of infantile myofibromatosis. The AgNORs were visualised as dots within the nuclei of the cells, and on the basis of their relative mean numbers of AgNORs fibrous proliferations of childhood could be easily differentiated from low grade infantile fibrosarcoma. The differences observed were significant (0.01 greater than p greater than 0.001). This technique, previously the province of the cytogeneticist, may be of use to the pathologist in differentiating infantile fibrous proliferations.

Nucleolar organizer regions in small cell tumours of childhood

A silver colloid technique for nucleolar organizer regions (AgNORs) was applied to paraffin sections of 50 small cell tumours of childhood. These comprised 20 neuroblastomas, 10 Ewing's sarcoma, and 20 rhabdomyosarcomas, including spindle cell, myxoid, and round cell variants. On the basis of the number of AgNORs, one could differentiate between the three groups. The differences observed were statistically significant (P = 0.01-0.001). The subtypes of rhabdomyosarcoma could not be distinguished from one another on the basis of AgNOR counts. We suggest that this simple histochemical technique may be a useful adjunct to the range of special techniques now available to assist the pathologist in the diagnosis of small round cell tumours.

Immunohistochemical localization of S100 protein in benign and malignant conditions of the breast

A peroxidase--antiperoxidase technique for S100 protein has been applied to 122 breast lesions from 122 patients. These included 35 cases of fibrocystic disease, 16 cases of sclerosing adenosis, 24 cases of papilloma and papillomatosis, 43 intraduct carcinomas, and four intralobular carcinomas. In fibrocystic disease, S100 protein was demonstrable in large amounts in cells between the duct lining cells and the basement membrane of the ducts, being most pronounced in those exhibiting adenosis. Areas of epitheliosis showed scattered positive cells within the ducts with more strongly positive cells around these ducts. Apocrine metaplasia was moderately positive. No S100 protein was demonstrable in the epithelial lining cells of cysts or within the stroma. In sclerosing adenosis individual cells and groups of cells in the fibrous tissue were strongly positive. In papillomatosis and papilloma, the vascular core and epithelium failed to stain, but a discontinuous layer of cells between the epithelium and basement membrane was positive. In intraduct and intralobular carcinoma the tumor cells were uniformly negative, and wherever fibrocystic disease was also present, S100 protein was variably demonstrable. The study corroborated the view that fibrocystic disease and benign proliferative processes of the breast appear to contain cells that correspond to myoepithelial cells, and suggests that S100 protein may serve as a useful marker in the separation of benign proliferative breast lesions from in situ carcinoma.

Immunohistochemical localization of S100 protein in skin tumors

We applied a peroxidase-antiperoxidase technique for S100 protein to 73 tumors of skin and skin adnexa. These included 15 eccrine tumors, 11 apocrine tumors, 18 tumors with differentiation toward hair, two sebaceous adenomas, one mixed tumor of the scalp, ten dermatofibromas, ten basal cell carcinomas, five squamous cell carcinomas, and one clear cell acanthoma. Consistent results were obtained. Occasional cells in eccrine tumors showed strong positive staining, as did the Langerhans' cells in the squamous cell carcinomas and the clear cell acanthoma. The cells of the apocrine tumors showed moderate to weak staining, and the tumors with differentiation toward hair, the sebaceous adenomas, and the mixed tumor of the scalp showed uniform negative staining, as did basal cell carcinomas and dermatofibromas.